Table of contents

Data science, hailed as the fourth paradigm of science, is a rapidly growing field which has served to revolutionize the fields of bio-informatics and climate science and can provide significant speed improvements in the discovery of new materials, mechanisms, and simulations. Data science techniques are often used to analyze and predict experimental data, but they can also be used with simulated data to create surrogate models. Chief among the data science techniques in this application is machine learning (ML), which is an effective means for creating a predictive relationship between input and output vector pairs. Physics-based battery models, like the comprehensive pseudo-two-dimensional (P2D) model, offer increased physical insight, increased predictability, and an opportunity for optimization of battery performance which is not possible with equivalent circuit (EC) models. In this work, ML-based surrogate models are created and analyzed for accuracy and execution time. Decision trees (DTs), random forests (RFs), and gradient boosted machines (GBMs) are shown to offer trade-offs between training time, execution time, and accuracy. Their ability to predict the dynamic behavior of the physics-based model are examined and the corresponding execution times are extremely encouraging for use in time-critical applications while still maintaining very high (∼99%) accuracy.

Li-ion batteries using the Li[Ni_0.8Co_0.15Al_0.05]O₂ (NCA) electrode containing an aqueous binder have been fabricated by a pressurized CO₂ gas treatment (PCT). With the PCT, the pH of the NCA slurry containing an aqueous binder significantly decreased from 12.2 to 8.3 in 3 minutes. The cyclability and coulombic efficiency were greatly improved and the retention rate of the discharge capacity at the 50th cycle with respect to that at the 1st cycle achieved 82%. A Li₂CO₃ layer may be formed on the NCA electrode surfaces during the PCT, and the corrosion reaction on the Al foil collector was significantly suppressed. The Li₂CO₃ layer is electronically insulating and prevents decomposition of the electrolyte during the cycling, resulting in a decreased film resistance (R_f) between the 25th and 50th cycles. On the other hand, without the PCT, the discharge capacity drastically decreased during the cycling. The aqueous binder may be degraded, the corrosion reaction on the Al foil collector occurred, and Al compound layers were formed on an Al foil collector. However, these layers didn't protect the NCA particle surfaces. Therefore, the electrolyte was decomposed during the cycling. These results caused an increase in the charge transfer resistance and R_f.

Adding esters as co-solvents to Li-ion battery electrolytes can improve low-temperature performance and rate capability of cells. This work uses viscosity and electrolytic conductivity measurements to evaluate electrolytes containing various ester co-solvents, and their suitability for use in high-rate applications is probed. Among the esters studied, methyl acetate (MA) outperforms other esters in its impact on the conductivity and viscosity of the electrolyte. Therefore, viscosity and conductivity were measured as a function of temperature and LiPF₆ concentration for electrolytes ethylene carbonate (EC): linear carbonate: MA in the ratio 30:(70-x):x, where linear carbonate = {ethyl methyl carbonate (EMC), dimethyl carbonate (DMC)}, and x = {0, 10, 20, 30}. Adding MA leads to an increase in conductivity and decrease in viscosity over all conditions. Calculations of electrolyte properties from a model based on a statistical-mechanical framework, the Advanced Electrolyte Model (AEM), are compared to all measurements and excellent agreement is found. All electrolytes studied roughly agree with a Stokes' Law model of conductivity. A Walden analysis shows that the ionicity of the electrolyte is not significantly impacted by either MA content or LiPF₆ concentration. Li[Ni_0.5Mn_0.3Co_0.2]O₂/graphite cells containing MA were cycled at charging rates up to 2C and showed improved cycling performance.

Oxygen and sulfur dual-doped 3D interconnected hierarchical porous carbons (HPCs) were synthesized via pyrolysis followed by chemical activation of natural alginate. The results showed that both an appropriate poristy and high level of S doping lead to the excellent electrochemical performance. The optimal HPC-Na-900/S composite exhibited outstanding electrochemical performance as cathode materials for Li-S batteries. Specially, the electrochemical performances of the resultant HPC/S composites change randomly with the surface area, pore volume except porosity and surface chemistry under the testing conditions. The porosity plays a more important role than surface area as well as pore volume which are the crucial parameters in designing of porous carbon, and only the ratio of these hierarchical pores reaches a specific range, the best battery performance can be achieved. The introduction of heteroatom are also key factors that determines the performance of lithium-sulfur batteries. This insight into the relation of microstructure and surface chemistry with battery performance can help to guide better understand and rationally design porous carbon hosts.

The poor thermal stability of conventional LiPF₆-based electrolytes is one of the major obstacles for today's lithium-ion batteries. Recently, lithium 4,5-dicyano-2-(trifluoromethyl)imidazolide (LiTDI) has demonstrated to be highly efficient in scavenging moisture from the electrolyte and thereby improving electrolyte stability. In this context, effects of the LiTDI additive on LiNi_1/3Mn_1/3Co_1/3O₂ (NMC)/graphite cells are evaluated at a temperature of 55°C. With the incorporation of LiTDI, an improved cycling performance of NMC/graphite cells was achieved, and the impedance increase at the NMC/electrolyte interface was significantly mitigated. Furthermore, LiTDI exhibited a profound influence on the interfacial chemistries in the full cell, and LiTDI-derived species were found on the surfaces of both the cathode and the anode. The SEI layer formed on graphite anodes was more homogenous in morphology and consisted of larger amounts of LiF and fewer oxygen-containing species, as compared to graphite in additive-free cells. This study shows that LiTDI is a promising electrolyte additive for NMC/graphite cells operated at elevated temperatures, highlighting that the influence of the LiTDI additive is worth exploring also in other battery chemistries.

With the aim of developing zinc-air batteries with a large capacity and long life, submicron ultrafine zinc-bismuth powders with a high surface area, high activity and low cost were prepared by a DC arc evaporation method. To reduce the corrosion rate of zinc-air batteries composed of ultrafine zinc-bismuth powders and to improve the charge and discharge performance of the zinc electrode, organic additives such as benzotriazole (BTA), thiourea (CH₄N₂S) and sodium dodecyl benzene sulfonate (SDBS) were added individually into the electrolyte. The hydrogen evolution rate of the zinc electrode composed of zinc-bismuth powders and the properties of zinc-air batteries were investigated by hydrogen evolution experiments and electrochemical tests. The adsorption mechanism of different electrolyte additives on the zinc electrode was studied based on SEM, Raman spectroscopy and electrochemical tests. The corrosion performance of BTA was the best of the single electrolyte additives. The charge-discharge performance and cycle performance of the zinc-air battery were greatly improved, and the corrosion inhibition efficiency of the zinc electrode was 76.9%. The capacity after 60 cycles was 458.2 mAh/g, and the capacity retention rate was 91%. Of the two-element compound electrolyte additives, the combination of BTA and SDBS was the best; the optimum corrosion inhibition efficiency of the zinc electrode was 88.5%, the capacity was 497.0 mAh/g after 60 cycles, and the capacity retention rate was 96%.

Li₂MnO₃ film synthesized on SrTiO₃ substrate with SrRuO₃ buffer layer using pulsed laser deposition has demonstrated a high initial charge-discharge capacity. It has been found that the Li₂MnO₃ crystals were composed of nano-domains with 5 nm in size, which followed a dominant orientation relationship (OR) with respect to the SrRuO₃ crystals at the Li₂MnO₃/SrRuO₃ interface. The domain size is in agreement with the calculated critical size, which is determined by the elastic strain originated from the lattice mismatch at the Li₂MnO₃/SrRuO₃ interface. We proposed that the high initial charge-discharge capacity of the Li₂MnO₃ film is due to the combined effects of (1) being able to release the lattice strain at the Li₂MnO₃ domain boundaries during (de)intercalation of Li-ions that causes lattice expansion and shrinkage, and (2) crystal structure of the nano-domains and their ORs with respect to the SrRuO₃ crystals being well-maintained due to the above strain release. In addition, our observation confirmed the existence of anti-phase domain boundaries and stacking faults in the Li₂MnO₃ crystals. However, it is considered that their influences on the (de)intercalation of Li-ions are not significant, because these defects do not obstruct the conduction paths of Li atoms that are orderly arranged in the c-planes.

Rechargeable magnesium batteries have attracted much interest due their high volumetric capacity, potential for safe operation, and the natural abundance of magnesium. However, the development of magnesium batteries for practical applications has been obstructed by the lack of understanding of the liquid structure of electrolytes. Herein, we use quantum density functional theory coupled with a continuum solvation model to investigate the structure of Mg(BH₄)₂ in two ethereal solvents: tetrahydrofuran (THF), and monoglyme (G1). The most energetically favorable clusters of Mg(BH₄)₂, MgBH₄⁺, and Mg²⁺, with associated solvent molecule ligands, are determined. The free energy required to generate monovalent ions in the electrolyte is positive and the formation of divalent complexes is prohibitive. Singly and doubly charged complexes are more stable in G1 than THF, which is consistent with experimental findings. From the standpoint of free energy, clusters containing multiple magnesium atoms are not favored. Theoretical ²⁵Mg-NMR, ¹¹B-NMR spectra, and infrared vibrational modes of borohydride were calculated for each cluster. The relationships between cluster charge and the signals of each spectrum are determined. These analytical descriptors could be useful to characterize the degree of ion dissociation in the electrolyte.

Li-rich Mn-Ni-Fe (MNF) oxide cathodes are emerging as a low-cost alternative to commercial Ni-Mn-Co (NMC) oxides with the cost of raw iron being three orders of magnitude lower than cobalt. MNF cathodes have demonstrated potential for high capacity and high discharge voltage cathodes, however, the capacity decay and instability of discharge voltage upon cycling still need to be resolved for their successful commercialization. Both phenomena are related to the changes in structure and in this study, we utilize SXRD and XAFS to investigate the structural changes correlated to electrochemical performance of Li_1.2Mn_0.5Ni_0.2Fe_0.1O₂ cathode. This material, prepared by sol gel synthesis, showed initial discharge capacity of 226 mAhg⁻¹ and 93% capacity retention after 100 cycles. Fitting of the XAFS results provided information on the changes in local environment of each transition metal atom. Such detailed information on atomic environment is reported for the first time and compared to prior studies of NMC cathodes. In the discharged state Mn atoms show a shift to lower oxidation state and an irreversible loss of oxygen near neighbors after cycling, while Ni and Fe show only minor changes in their environment. An observed 5.87% lattice expansion after cycling is suggested to contribute to voltage fade.

The necessity of developing Ni-rich layered oxides cathode materials with more than 90% of Ni content is rapidly increasing for satisfying the demand of achieving the high capacity of Li-ion batteries. However, including more Ni contents results in increased formation of undesirable Li residues at the surface as well as deteriorating several types of degradation behaviors during cycling, which are the critical factors of design rules for the cathode material. In this study, the facile synthesis of an electrochemically active material, LiCoO₂, is realized at the surface of LiNi_0.91Co_0.06Mn_0.03O₂ via the conventional dry coating method utilizing the Li-reactive capability of Co₃O₄. First-principles calculations are performed to investigate the possible formation of LiCoO₂ from the phase diagram. The formation of the electrochemically active coating material considerably reduces the Li residues, increases the capacity, and exhibits a better cycle life with enhanced rate capability. The presence of LiCoO₂ phase is verified from transmission electron microscopy (TEM) images, energy-dispersive X-ray spectroscopy (EDS) elemental mapping, and electron energy loss spectroscopy (EELS) spectra. Superior performance of Co₃O₄ is further demonstrated by comparing the results with those from conventional coating materials of Al₂O₃, TiO₂, V₂O₃, and ZnO, whose electrochemical performance is worse in all of aspects.

A composite of bismuth and carboxymethyl cellulose (Bi@CMC) was successfully prepared and used as an additive in rechargeable Zn–Ni battery. The Bi@CMC composite combines the characters of electric conduction, hydrogen evolution reaction (HER) suppression and hydrophilicity, since hydrophilic carboxymethyl cellulose (CMC) fibers are coated by high-HER overpotential Bi particles. A Zn–Ni battery using an anode containing Bi@CMC demonstrated a higher coulombic efficiency and discharge capacity than pristine CMC. In addition, the rationality of the method which utilized the KOH/Zn(OH)₄²⁻ electrolyte to alkaline rechargeable zinc-based batteries is discussed.

The FeF₃·0.33H₂O nanoparticles packaged into three-dimensional order mesoporous carbons (3D-OMCs) as cathode material of sodium-ion batteries (SIBs) was deliberately designed and fabricated by a facile nanocasting technique and mesoporous silica KIT-6 template. The structure, morphology, elemental distribution and electrochemical performance of FeF₃·0.33H₂O@3D-OMCs nanocomposite are investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscope (TEM), energy-dispersive X-ray spectroscope (EDS), Raman spectroscopy and electrochemical measurement. The results show that the as-synthesized FeF₃·0.33H₂O nanoparticles are perfectly packaged in 3D-OMCs matrix, and the size and morphology of FeF₃·0.33H₂O nanoparticles can be effectively controlled. Furthermore, it has been found that the FeF₃·0.33H₂O@3D-OMCs nanocomposite can deliver a high first discharge capacity of 386 mAh g⁻¹ and excellent capacity reservation after 100 cycles at a rate of 20 mA g⁻¹ in the voltage range of 1.0–4.0 V. Especially, even up to 100 mA g⁻¹, the discharge capacity is still as high as 201 mAh g⁻¹, indicating a remarkable rate capability. The excellent electrochemical properties of FeF₃·0.33H₂O@3D-OMCs nanocomposite can be because the 3D mesoporous structure of 3D-OMCs can provide an expressway of electron transfer for Na⁺ insertion/extraction, and alleviate the drastic volume variation of FeF₃·0.33H₂O in the charge-discharge process.

Cyclic voltammetry and electrochemical impedance spectroscopy were applied to investigate the effect of the concentration of KOH solution on the capacitive performance of the nanostructured vanadium nitride. The results reveal that the required overpotential for the transformation of V²⁺ to V³⁺ in concentrated KOH solutions is much lower than that in diluted solutions, indicating that concentrated solutions are kinetically more favorable than diluted solutions. Additionally, a marked decrease in charge transfer resistance and electrolyte series resistance were observed as the concentration of KOH solution increased. Thus, the specific capacitance and the rate capability of the vanadium nitride electrode are improved with increasing of the concentration of KOH solution. Moreover, the specific capacitance of the vanadium nitride material in 6 M KOH solution is the highest, and the vanadium nitride material exhibits great long term stability in KOH solution.

The thermal stability of lithium ion batteries was studied by means of Accelerating Rate Calorimetry in Heat-Wait-Search operation on both electrode and cell level. Fresh and aged samples were investigated depending on the state-of-charge (SoC) of a 5 Ah pouch cell comprising mesocarbon microbeads and LiNi_0.4Co_0.2Mn_0.4O₂ as the anode and cathode materials. 1 M LiPF₆ in EC:DEC 3:7 (by weight) containing 2 wt% VC and 0.5 wt% LiBOB was chosen as the electrolyte. Measurements on the electrode level revealed a higher self-heating rate (SHR) of the cathode compared to the anode for all SoC and state-of-health (SoH) combinations in the temperature range where a self-sustaining decomposition reaction could be detected. A lower SoC showed a lower SHR of the electrode/electrolyte mixture with no reaction detected on the anode side ≤ 50% cell SoC. Cyclic aging led to a decrease in thermal stability of the cathode at lower SoC values with no significant influence on the anode implying a larger safety threat on the cell level. Avrami-Erofeev and autocatalytic reaction models were used to quantify the influences of SoC and SoH on reaction kinetics. Full cell measurements confirmed the observations at a higher SHR.

In this work we discuss the degradation chemistry on carbon-free electrodes of two ether based electrolytes for Li-O₂ batteries, i.e. tetraethylene glycol dimethyl ether (TEGDME) and dimethoxy ethane (DME) with lithium trifluoromethane sulfonate (LiTfO) as salt. To this aim we developed an all-metallic positive electrode by electrodeposition of a gold dendritic film on a nickel foam (Au@Ni). These carbon-free electro-catalytic electrodes have been used to investigate the degradation chemistry of the electrolytes in Li-O₂ cells by eliminating the parallel parasitic reactions due to the commonly used carbon electro-catalysts. In particular the composition and morphological evolutions of the Au@Ni electrodes after discharge and cycling have been characterized ex situ by Raman Spectroscopy, X-ray Photoemission Spectroscopy and Scanning Electron Microscopy. We also couple this experimental study with thermodynamic predictions about the onset degradation of the DME molecule based on density functional theory calculations. In summary in both DME/LiTfO and TEGDME/LiTfO electrolytes, the degradation involves the oxidation of the ether solvent to a mixture of carbonates and carboxylates/formate/oxalate. DME is apparently more strongly degraded compared to TEGDME whereas the LiTfO anion is highly stable. Calculations suggest the key role played by the singlet oxygen molecule as initiator of the degradation path.

Physical properties of LiPF₆ in ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) electrolytes were studied by conductivity measurements, Fourier transform infrared spectroscopy (FT-IR) and differential thermal analysis (DTA). Conductivity measurements show that the addition of additive levels of FEC to EMC electrolyte can dramatically increase the conductivity of EC-free EMC electrolytes at low salt concentrations below 0.4 M. FT-IR results show that the added FEC hinders ion pair formation by competing with EMC to dissociate LiPF₆ resulting in increased conductivity in EMC electrolytes. Conductivity measurements show that the conductivity of DMC electrolytes decreases significantly below 0°C due to the high melting point of DMC. Differential thermal analysis was used to determine the LiPF₆-DMC phase diagram which then can be used to explain the conductivity results. The results presented here identify avenues by which EC-free electrolytes can be improved for use in practical Li-ion cells.

Layered LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) is one of the high-energy positive electrode (cathode) materials for next generation Li-ion batteries. However, compared to the structurally similar LiNi_1/3Mn_1/3Co_1/3O₂ (NMC111), it can suffer from a shorter lifetime due to its higher surface reactivity. This work studied and compared the formation of surface contaminations on NMC811 and NMC111 when stored under ambient conditions using electrochemical cycling, Raman spectroscopy, and X-ray photoelectron spectroscopy. NMC811 was found to develop a surface layer of up to ∼10 nm thickness that was mostly composed of nickel carbonate species mixed with minor quantities of hydroxide and water after ambient storage for 1 year, while no significant changes were observed on the NMC111 surface. The amount of carbonate species was quantified by gas chromatographic (GC) detection of carbon dioxide generated when the NMC particles were dispersed in hydrochloric acid. Surface impurity species formed on NMC811 upon ambient storage not only lead to a significant delithiation voltage peak in the first charge, but also markedly reduce the cycling stability of NMC811-graphite cells due to significantly growing polarization of the NMC811 electrode.

LiNi_0.5Co_0.2Mn_0.3O₂ (NCM) and LiMn_0.6Fe_0.4PO₄ (LMFP) mixtures are prepared and intensively investigated in a practical level. The 18650 full batteries that are assembled with NCM-LMFP mixtures as cathodes exhibit better rate capability than cells that are utilized LMFP material as the cathode. Moreover, energy densities of 18650 batteries that are fabricated with NCM-LMFP mixtures as cathodes are not largely reduced with the reduced amount of NCM because of the high voltage plateau of LMFP material, but contrary, the cost of cathode materials is remarkably decreased. The cycling stability of batteries that are prepared with NCM-LMFP mixtures as cathodes is better than cells that are assembled with NCM as the cathode. In addition, the low/high-temperature performance of cells that are fabricated with mixture materials as cathodes is superior to batteries that are assembled with LMFP as the cathode. These electrochemical test results demonstrate that NCM-LMFP mixtures combined the advantages of the two materials, implying good synergetic effects between NCM and LMFP materials. Therefore, lithium ion batteries fabricated with NCM-LMFP mixtures as cathodes with high energy density, superior rate capability, long lifetime, excellent temperature adaptability and low cost would be a promising candidate batteries for electric vehicles.

The zinc air battery has been regarded as an efficient solution to renewable energy storage applications in the next generation. Zinc air chemistries are promising, though great challenges still remain to utilize their high energy, optimize efficiency and high discharge rate. Here, we demonstrate an improved zinc air battery by replacing NaOH, used in our previous study, with KOH as an additive to the molten Li_0.87Na_0.63K_0.50CO₃ eutectic electrolyte. Cycling tests showed a very stable performance through 150 charge-discharge cycles, exhibiting high coulombic efficiency (94%) and an average discharge potential of ∼1.08 V when charged at a constant current of 75 mA and discharged over a constant 100Ω load to 0.8 V cutoff at 550°C. Moreover, rate tests revealed a good performance even at high rates of cycling, maintaining a coulombic efficiency of over 90% while at 7.3 C. These results show marked improvements in the field of rechargeable zinc air batteries.

The potential of internal short circuit (ISC) increases due to the attempt to cram more active materials in a limited volume, when designing battery with higher energy density. Since the mechanism of ISC formation in lithium ion batteries is still unclear, it is essential to develop effective ISC detection algorithm. This paper provides an in-depth analysis on the fault features for ISC detection using a validated electrochemical-thermal coupled model. The modelling analysis unveils the fault features of ISC, and the difference of state-of-charge and the heat generation power are regarded as promising indicators for further development of fault diagnosis algorithms.

A long-term in-situ measurement method for evolved gases in commercial 18650 cylindrical lithium ion batteries (LIBs) is proposed using Raman spectroscopy. Hydrogen, methane, carbon dioxide, and carbon monoxide were the main gases detected from cells at 4.2–4.8 V for 1800 h. Gas evolution rates were determined by the aging time and the staying potential, resulting in a nonlinear partial-pressure-dependence as a function of the aging time. Initially, the evolution of carbon dioxide and carbon monoxide was significant. After potential-dependent onset times, hydrogen and methane generation increased suddenly. At low potential ranges of 4.2–4.4 V, mostly hydrogen gas was generated, whereas at high potential ranges (>4.6 V), methane becames dominant. Even at 4.4 V, importantly, the absolute accumulative H₂ gas pressure was >3 atm, raising the requirement to monitor such gas for better safety even under nominal operating conditions. Moreover, cumulative partial pressures of the detected gases exceeded the range 5–10 atm, which was associated with the staying potential. An evolution mechanism through which the gas is converted from hydrogen to methane is proposed and discussed. The electrochemical analysis of the aged LIBs showed that the capacity fade was accelerated by the increase in the staying potential while the resistances remained similar.

Currently, finding a suitable anode material for sodium-ion batteries (NIBs) is the major challenge as graphite is not an ideal anode candidate. Recently, organic anode materials hold promise as potential alternatives. In this study, naphthalene based dicarboxylate (Na₂-NDC) has been explored as anode material for NIBs. The electrochemical sodiation/desodiation process of Na₂-NDC is a biphasic reaction and it shows a good capacity retention even after 100 cycles. Ex-situ XRD studies reveal structurally robust nature of Na₂-NDC during sodiation/desodiation process. Moreover, the Na₂-NDC anode was paired with Na₃V₂O₂(PO₄)₂F/rGO cathode and demonstrated a full cell for the first time.

For reliable lifetime predictions of lithium-ion batteries, models for cell degradation are required. A comprehensive semi-empirical model based on a reduced set of internal cell parameters and physically justified degradation functions for the capacity loss is developed and presented for a commercial lithium iron phosphate/graphite cell. One calendar and several cycle aging effects are modeled separately. Emphasis is placed on the varying degradation at different temperatures. Degradation mechanisms for cycle aging at high and low temperatures as well as the increased cycling degradation at high state of charge are calculated separately. For parameterization, a lifetime test study is conducted including storage and cycle tests. Additionally, the model is validated through a dynamic current profile based on real-world application in a stationary energy storage system revealing the accuracy. Tests for validation are continued for up to 114 days after the longest parametrization tests. The model error for the cell capacity loss in the application-based tests is at the end of testing below 1% of the original cell capacity and the maximum relative model error is below 21%.

The energy density of a non-aqueous redox flow battery (naRFB) is directly related to the active species concentration, cell voltage, and the number of electrons transferred per redox process. One strategy to increase the energy density is to mix multiple active components, which has the effect of increasing the overall concentration and the number of electrons transferred. In this study, ferrocene with TEMPO and cobaltocenium hexafluorophosphate with N-methylphthalimide were evaluated to be posolyte and negolyte mixtures, respectively. The resulting naRFB system exhibit two one-electron redox processes that establish a cell voltage of 1.8 V at a 50% state-of-charge. There were no interactions between the active species in electrolyte mixtures as observed by cyclic voltammetry, chronoamperometry and UV-vis absorbance spectroscopy. Charge-discharge experiments further demonstrated the suitability of the proposed electrolyte mixtures for naRFB applications.

LiNiO₂ is a promising cathode material for lithium ion batteries because of its high specific capacity (approximately 220 mA h g⁻¹). However, there are several challenging issues in the development of LiNiO₂, including its poor cycle and rate performance because of its structural deterioration due to thermodynamically unstable Ni³⁺. This paper demonstrates the role of Na⁺ in the electrochemical performance and structural stability of [Li_1-xNa_x]NiO₂ (x = 0, 0.005, 0.01, 0.025, and 0.05). Charge disproportionation Ni³⁺ → Ni²⁺ and Ni⁴⁺ in LiNiO₂ increases the cation mixing of Li⁺ and Ni²⁺ during cycling, resulting in the poor cycle performance of LiNiO₂. However, Na⁺ in [Li_1-xNa_x]NiO₂ mitigates the charge disproportionation because of the larger size of Na⁺ than Li⁺, leading to the improved structural stability of [Li_1-xNa_x]NiO₂. Consequently, Na⁺-doped LiNiO₂ alleviates the increase in the cation mixing of Li⁺ and Ni²⁺ during cycling compared to bare LiNiO₂. This results in the improved cycle performance of [Li_1-xNa_x]NiO₂ (x = 0.05), such as approximately 76% of capacity retention after 100 cycles. Moreover, the substitution of Li⁺ with Na⁺ in LiNiO₂ improves the storage characteristics of [Li_1-xNa_x]NiO₂, leading to a negligible capacity loss even after long-term storage.

Low cost non-woven fabric cannot be used as separator in lithium ion battery due to its asymmetrically large pores that easily lead to short circuit of a battery. We introduce a convenient method by coating blended copolymer onto both sides of non-woven fabric to make it possibly use in high voltage lithium ion battery in this paper. Cellulose acetate phthalate (CAP) copolymer is used as secondary copolymer to blend with poly(vinylidene fluoride-hexafluoropropylene) (P(VdF-HFP)) copolymer to offset the disadvantage of P(VdF-HFP) with low ionic conductivity and poor interfacial compatibility. It is found that the PC2 blended GPE shows better electrolyte uptake and higher ionic conductivity. When cycled at the voltage range of 3.0 V and 4.4 V, CR2025 coin cell with the structure of Li/GPE/LiCoO₂ exhibits acceptable cyclic stability and rate performance. After 100 cycles, the blended GPE based coin cell keeps 79% of original discharge capacity compared with that traditional Celgard Polyethylene membrane (saturated with liquid electrolyte) remains 77% of capacity, although non-woven fabric membrane falls down to no capacity after 7 cycles. Additionally, LiCoO₂ cathode combined with blended GPE still shows a high discharge capacity of 158 mAh g⁻¹ at 2C, remaining 91.3% capacity of 0.1C rate.

Nonaqueous redox flow batteries (RFBs) with an organic electrolyte can work at voltages higher than 2.1 V, thanks to the excellent electrochemical stability of such electrolytes. However, the biggest challenge related to nonaqueous RFBs is that the electrochemically active salts used in these batteries exhibit lower solubilities in organic electrolytes compared to those in aqueous electrolytes. In this study, bis(trifluoromethanesulfonyl)imide (TFSI) is investigated as the counter anions for the complexes of iron and nickel tris(2,2'-bipyridine) ((Bpy)₃) for use as electrolytes in high-energy RFBs. The synthesized salts were characterized systematically through ab-initio calculations, nuclear magnetic resonance (NMR), inductively coupled plasma mass spectrometry (ICP-MS) and electrochemical analyses. Ni(Bpy)₃(TFSI)₂ and Fe(Bpy)₃(TFSI)₂ containing bulky imide anions exhibit the improved solubility by weakening inter-anion Coulombic interactions, via charge delocalization.

The Na₃V₂(PO₄)₂F₃/Carbon Na-ion battery technology is appealing because of its high energy and power density, hence the need to assess its viability under practical operation. Here we provide a comprehensive understanding of its storage and cycling performances in various electrolytes and at different temperatures via a through differential voltage (dV/dQ) analysis of the data obtained from coin and pouch cells. The cells show excellent long-term cycling performance (capacity decay less than 0.020 mAh g⁻¹ per cycle at 1C rate whatever the electrolytes), but suffer at 55°C from copious self-discharge stemming from either reduction or oxidization of electrolytes. We could deduce, from monitoring side reactions rate as a function of temperature, the activation energies of 34 and 29 kJ mol⁻¹ for the parasitic reactions proceeding at the anode and cathode side, respectively. We hope our analysis protocol to be widely implemented for the fundamental investigation of side reactions between electrode and electrolyte interface in Na-ion battery; a must for optimizing battery performances via the screening of various electrolyte formulations.

Despite the accuracy and non-intrusive nature of Electrochemical Impedance Spectroscopy, the impedance spectra of commercial Lithium-ion cells are notoriously hard to interpret. Consequently, the literature is filled with various equivalent circuit models, which differ greatly in their physical significance, but which produce very similar impedance spectra. In this paper, explicit formulas are given to convert between various equivalent circuits made of resistors and capacitors of the sort discussed in the literature. Furthermore, all these formulas have been implemented in a Python program, in the hope that studies done assuming one circuit might be compared to studies done with a different circuit, for instance. This paper considers cases where two different circuits can produce two impedance spectra which are identical. For instance, explicit conversions are given between Ladder circuits, Voight circuits, and Maxwell circuits for various time constants. This gives a conceptual foundation to explore the more difficult case of circuits producing impedance spectra which are similar to each other (e.g. within 5%).

Iron molten air batteries are a promising technology for clean and efficient electrical power generation, but their durability is a key challenge to commercialization. Here, we replaced LiCl in the KCl-LiCl-LiOH system with Li₂SO₄ or Li_0.87Na_0.63K_0.50CO₃ to investigate electrode corrosion and improve cycle life. The nickel air electrode exhibited low corrosion rate in KCl-Li₂SO₄-LiOH, but the kinetics of the air electrode reactions was impaired. Electrolyte composition influences pitting corrosion of the Ni air electrode in KCl-LiCl-LiOH and intercrystalline corrosion in KCl-Li₂SO₄-LiOH. KCl-LiNaKCO₃-LiOH is a superior electrolyte for these iron air batteries with nickel air electrode. A tenacious, compact Li nickel oxide nano-scale particle layer on the nickel air surface in KCl-LiNaKCO₃-LiOH retards nickel fin matrix (current collector) corrosion allowing long-term use. The air electrode surface is an electrocatalytic layer of uniform nano-particles. The iron molten air battery cycled for 850 cycles with an average coulombic efficiency of 88.6% and average discharge potential of ∼1.04 V, achieving a ten-fold increase in cycle life in contrast with the previous result using KCl-LiCl-LiOH. This study explores key factors improving the Ni air electrode and cycle life without interfering with the cycling performance of the iron molten air battery.

The full electrochemical utilization of a crude micron-silicon anode is enabled by a simple and scalable cyclized-polyacrylonitrile (cPAN) electrode architecture paired with an innovative room temperature ionic liquid (RTIL) electrolyte. Field emission scanning electron microscopy, transmission electron microscopy, and electron energy loss spectroscopy show that the resilient cPAN coating mechanically contains the cycling-induced expansion, contraction, and fragmentation of the oversized silicon particles while an electrochemically robust solid-electrolyte interphase (SEI) layer prevents the perpetuation of irreversible side reactions. Prolonged electrochemical cycling data demonstrates unprecedented performance in both half-cell and full-cell configurations. Implementation of the micron-silicon anode constitutes a significant development in the evolution of safe and commercially-viable high-performance lithium-ion batteries.

The reduction products of common lithium salts for lithium ion battery electrolytes, LiPF₆, LiBF₄, lithium bisoxalato borate (LiBOB), lithium difluorooxalato borate (LiDFOB), and lithium trifluorosulfonylimide (LiTFSI), have been investigated. The solution phase reduction of different lithium salts via reaction with the one electron reducing agent, lithium naphthalenide, results in near quantitative reactions. Analysis of the solution phase and head space gasses suggests that all of the reduction products are precipitated as insoluble solids. The solids obtained through reduction were analyzed with solution NMR, IR-ATR and XPS. All fluorine containing salts generate LiF upon reduction while all oxalate containing salts generate lithium oxalate. In addition, depending upon the salt other species including, Li_xPF_yO_z, Li_xBF_y, oligomeric borates, and lithium bis[N-(trifluoromethylsulfonylimino)] trifluoromethanesulfonate are observed.

A new method is introduced for determining unknown concentrations of major components in typical lithium-ion battery electrolytes. The method is quick, cheap, and accurate. Machine learning techniques are used to match features of the Fourier transform infrared (FTIR) spectrum of an unknown electrolyte to the same features of a database of FTIR spectra with known compositions. With this method, LiPF₆ concentrations can be determined with similar accuracy and precision as an inductively coupled plasma optical emission spectrometry (ICP-OES) method. The ratios of organic carbonate solvent species can be determined with more rapidity than gas chromatography (GC). This FTIR method is faster and less expensive than GC and ICP-OES, and has the added benefit of being able to determine LiPF₆ concentration and solvent fractions simultaneously. Application of this tool can facilitate electrolyte analysis of aged lithium-ion cells, and will help elucidate mechanisms for cell degradation.

Sodium ion batteries with low cost and high capacities have attracted much attention. Herein, P2-type Na_2/3Fe_1/2Mn_1/2O₂ is synthesized by self-combustion method and characterized for physicochemical and electrochemical properties. The XRD confirms that the sample is formed in a pure phase. Cyclic voltammograms of electrodes are characterized by two well-defined pairs of peaks corresponding to redox processes in two different stages. The electrochemical studies as a cathode for sodium ion batteries are investigated in the 1.5–4.2 V range using Na metal as anode. An initial discharge capacity of about 210 mAh g⁻¹ is obtained at C/10 rate.

Severe self-corrosion is the main barrier preventing the application of aluminum as an anode material in alkaline air battery. In this work, a hybrid organic/inorganic inhibitor based on L-Cysteine/zinc oxide was tested to see if its addition to alkaline electrolyte can reduce self-corrosion of a commercial 1060 pure aluminum. Results obtained have shown that self-corrosion of pure aluminum is significantly restrained by the L-Cysteine/ZnO hybrid inhibitor without affecting its discharge performance. An interaction between ZnO and L-Cysteine leads to formation of a dense layer on pure aluminum surface. In both NaOH + ZnO and NaOH + L-Cysteine + ZnO solutions, the reaction mechanism is mainly controlled by diffusion of zincate ions. By using the L-Cysteine/ZnO hybrid inhibitor, cheap commercial 1060 pure aluminum can replace expensive 5N5 super-pure aluminum to achieve a comparable performance. This has been demonstrated in this study by comparing the battery based on commercial 1060 pure aluminum with the L-Cysteine/ZnO inhibitor and the battery made of 5N5 super-pure aluminum with 4 M NaOH solution.

The paper focuses on the performance and aging behavior of lithium nickel cobalt manganese oxide commercial standard material (NCM-111) which is improved with a post synthesis process in order to enhance the cathode active material of lithium-ion pouch cells regarding their capacity and cyclic stability. The aging behavior of the cells is analyzed with electrochemical impedance spectroscopy (EIS) during long-term electrochemical load cycling tests based on the Common Artemis Driving Cycle (CADC). Additionally, post-mortem investigations using scanning electron microscopy (SEM) and X-ray diffraction (XRD) were performed. The results demonstrate that post-processing of electrode active material is an effective tool to improve the properties of lithium-ion electrode materials, especially regarding high energy applications and lifetime optimization. The paper bridges the gap between lithium-ion battery electrode material development and the necessary cell testing under automotive relevant conditions which is important for the evaluation of new lithium-ion battery materials for automotive applications.

Expanded graphite (EG) - polypyrrole (PPy) hybrid nanocomposites are used for the fabrication of paper-based highly flexible supercapacitor devices. Brush-painted EG electrodes are utilized as electrodes for the electrodeposition of PPy, resulting in the formation of nanocomposite electrodes with the desired material loading. Fabricated paper-based electrodes are free from heavy current collectors, binders, and conductive additives. Within nanocomposite electrodes, expanded graphite layer on paper facilitates the charge transfer and conformal PPy layer atop improves capacitance through pseudocapacitance. Fabricated nanocomposite electrodes are highly flexible, thanks to excellent mechanical integrity among paper, EG and PPy components. A specific capacitance of 177.8 F g⁻¹, in conjunction with a capacity retention of more than 94.9% is obtained following 5000 cycles. With the simple fabrication and promising electrochemical performance obtained herein, fabricated paper-based nanocomposite supercapacitors are envisaged for utilization as power sources in paper electronics.

A cation disordered Li₂MnO₃ with NaCl type structure is found to show good electrochemical performance. The initial charge profile of the disordered Li₂MnO₃ shows a plateau at 4.1 V, while the ordered Li₂MnO₃ shows a plateau at 4.4 V. The good electrochemical activity affects the subsequent electrochemical performance, i.e., its initial charge and discharge capacities are 410 mA h g^{− 1} and 320 mA h g^{− 1}. An iodometry and an X-ray fluorescence reveals that Mn ion in Li₂MnO₃ reduces from 4+ to ca. 3.7+ accompanying some amount of O₂ release from Li₂MnO₃, during the disordering process. Such oxygen deficiency might be one of the key factors that improves the initial electrochemical activity of the Li₂MnO₃(4+). Ex-situ XRD reveals that the lattice size of the disordered Li₂MnO₃ changes by about 3% during cycling.

The quantitative analysis of electrochemical impedance spectroscopy (EIS) data is important for both characterization and prognostic applications in many electrochemical systems. Here we describe an open-source platform, the ImpedanceAnalyzer, for easy-to-use physics-based analysis of experimental EIS spectra. To demonstrate the use of the platform, we explore the basic capabilities of the pseudo two-dimensional (P2D) battery model to predict publicly available experimental EIS data from a 1500 mAh commercial lithium-ion (LiCoO₂/graphite) cell. An a priori computed dataset of 38,800 P2D-based impedance spectra simulations, covering a wide range of frequencies (1 mHz to 100 kHz) and model parameters, enables a straightforward least squares matching approach for analyzing experimental spectra. We find an average error of 1.73% between the best-matching computed spectrum from the 38,800 member library and the experimental spectrum being analyzed. Our analysis shows there is significant opportunity to improve the fit between experimental data and physics-based impedance simulations by a combination of a larger computed dataset, local optimization, and further additions to the model physics. The approach and open source tools developed here can be easily extended to other electrochemical systems.

This study investigates biochar supercapacitor electrodes made several times larger than those in commercial application, using both thick monolithic and powder thin film structures. Slow-pyrolysis of wood precursors produces carbonized biochar monoliths which retain the internal structures of biomass. While this natural network of transportation channels for water and nutrients was not found to facilitate ion migration in capacitive charge/discharge cycles, monolithic electrodes revealed lower intrinsic resistances than thin films containing PTFE binder. As a consequence, monolithic electrodes up to 5 mm thick show equivalent specific capacitance performance to their thin film counterparts. This feature could allow greater energy density storage per device.

Cell performance of lithium-ion-batteries (LIB) can be tailored to particular hybrid or full electric vehicle applications by targeted adjustment of manufacturing parameters. Furthermore there is a large number of cathode material compositions which can be used. Knowing the correlations between these parameters, electrode structures and cell performance is important to reach the high requirements posed by electromobility. Within this study, impacts of essential manufacturing parameters, being active material mass loading, calendering stress load and carbon black content on the cell performance were investigated for two different, promising cathode materials. For NMC and LMO, the respectively highest calendering stress load and carbon black content yielded the best performance as losses due to poor electronic conductivity were reduced. The active material mass loading rather influenced the ratio between specific energy and specific power. Finally two optimally performing parameter configurations could be identified which were, depending on the required application: NMC with high mass loading and LMO with medium mass loading; in both cases the highest calendering load and carbon black content were applied. An analysis of statistical reproducibility dependent on various parameter configurations was carried out as well. A significant improvement of reproducibility could be achieved by increase of calendering stress load.

It has been shown recently that the overpotential originating from ionic conduction of alkali-ions through the inner dense solid-electrolyte interphase (SEI) is strongly non-linear. An empirical equation was proposed to merge the measured resistances from both galvanostatic cycling (GS) and electrochemical impedance spectroscopy (EIS) at 25°C. Here, this analysis is extended to the full temperature range of batteries from −40°C to +80°C for Li, Na, K and Rb-metal electrodes in carbonate electrolytes. Two different transport mechanisms are found. The first one conducts alkali-ions at all measured temperatures. The second transport mechanism conducts ions for all seven measured Li-ion electrolytes and one out of four Na-ion electrolytes; however, only above a certain critical temperature T_C. At T_C a phase transition is observed switching-off the more efficient transport mechanism and leaving only the general ion conduction mechanism. The associated overpotentials increase rapidly below T_C depending on alkali-ion, salt and solvent and become a limiting factor during galvanostatic operation of all Li-ion electrolytes at low temperature. In general, the current analysis merges the SEI resistances measured by EIS ranging from 26 Ωcm² for the best Li up to 292 MΩcm² for Rb electrodes to its galvanostatic response over seven orders of magnitude. The determined critical temperatures are between 0–25°C for the tested Li and above 50°C for Na electrolytes.

Lithium-rich ternary cathode material Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ and K⁺–doped Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ materials have been successfully prepared via co–precipitation method, followed by a high-temperature solid state process. The chemical component, crystal structure and morphology, surface valence states are conducted by ICP, XRD refinement, FESEM and XPS analysis. Electrochemical properties and Li⁺ diffusion behavior have been extensively studied. The Rietveld refinement results reveal that the c/a ratio increases induced by K⁺ doping. Electrochemical studies indicate that the reasonable amount of K⁺–doped material exhibits the better cycling stability and rate performance. The study indicates that K⁺ doping hinders the lithium ions migration, thus excesses of K⁺ doping leads to the cycling stability and rate performance degradation.

This paper presents an approach to quantify microstructural inhomegeneity in lithium ion battery electrodes over multiple length scales and examines the impact of this microstructural inhomogeneity on electrochemical performance. Commerical graphite anodes are investigated because graphite remains the anode material of choice due to its low cost, mechanical robustness, and suitable electrochemical properties. At the same time, the graphite anode often plays a role in cell degradation and failure, as lithium plating can occur on the graphite anode during charge, when unfavorable microstructure in the graphite electrode leads to a large overpotential. Here, three-dimensional representations of four different commercial anodes obtained with X-ray tomographic microscopy are statistically analyzed to quantify the microstructural inhomogeneity that is commonly present in lithium ion battery electrodes. Electrochemical simulations on the digitalized microstructures are performed to isolate and understand the influence of different types of microstructural inhomogeneity on battery performance. By understanding how distributions in particle size and shape or slurry and electrode processing cause microstructural inhomogeneity and impact performance, it is possible to determine the extent to which homogeneity should be prioritized for specific applications and how homogeneity could be achieved through smart material selection and processing.

Lithium manganese oxide cathodes used in Li-ion batteries suffer from manganese dissolution and capacity fade. We present a new technique for directly measuring the manganese ion (Mn²⁺) concentration in a typical Li-ion carbonate electrolyte using 4-(2-pyridylazo) resorcinol (PAR) as a UV-vis probe. Chelation between PAR and Mn²⁺ ion induces a characteristic absorption peak where the peak intensity corresponds to Mn²⁺ ion concentration in the electrolyte. Electrochemical stability of the probe is verified by performing potential hold and cyclic voltammetry. The in situ characterization of Mn dissolution in a customized battery cell is performed during cyclic voltammetry.

Electrochemical intercalation of lithium ions was investigated in propylene carbonate (PC)-trimethyl phosphate (TMP) electrolyte solution. Intercalation of lithium ions took place in 1 mol dm⁻³ lithium bis(trifluoromethanesulfonyl)amide (LiTFSA)/PC:TMP by adding a certain amount of calcium ions. When the molar ratio of PC:TMP:Li⁺ was 6:6:1, lithium-ion intercalation took place when the molar ratio of Ca²⁺/Li⁺ was 1.2. The criteria was Ca²⁺/Li⁺ = 0.8 when the molar ratio of the electrolyte was PC:TMP:Li⁺ = 2:10:1. It was suggested from Raman spectra that the solvation structure of lithium ions were altered from the four coordinated tetrahedral configuration in the case that intercalation reaction occurred. This change in the lithium-ion solvation structure was caused by adding calcium ions, which has stronger Lewis acidity than lithium ions. Different criteria of Ca²⁺/Li⁺ molar ratio for lithium-ion intercalation by the difference of PC:TMP:Li⁺ molar ratio shows that the lithium-ion solvation structure was also affected by the electrolyte composition.

The cycle stability and initial Coulombic efficiency (ICE) of molybdenum dioxide (MoO₂) are generally inferior as anode materials for lithium ion batteries. Herein, we report a facile self-transition strategy to prepare a hierarchically nanostructured Cu-MoO₂/reduced graphene oxide (rGO) composite. The prepared Cu-MoO₂/rGO composite exhibits a reversible capacity as high as 970 mAh g⁻¹ after 200 discharge/charge cycles at 100 mA g⁻¹, superior ICE (80.4%), and excellent cyclability (607 mAh g⁻¹ even after 600 discharge/charge cycles at 500 mA g⁻¹ with a Coulombic efficiency of 98.8%). The enhanced electrochemical performance is attributed to the formation of a multi-hierarchical nanostructure of Cu-MoO₂/rGO composite. Such a unique structure well adapts to the volume variation of MoO₂ upon cycling and greatly enhances the kinetics of charge transfer. Furthermore, the homogeneous dispersion of Cu nanocrystallites among the MoO₂ crystals not only creates the conductive path in the whole structure, but also provides sufficient channels for Li⁺ insertion/extraction. These results are envisaged to pave the way toward the rational design and fabrication of nanostructured electrode materials with enhanced electrochemical properties for next-generation lithium ion batteries.

Understanding the factors limiting Li⁺ charge transfer kinetics in Li-ion batteries is essential in improving the rate performance, especially at lower temperatures. The Li⁺ charge transfer process involved in the lithium intercalation of graphite anode includes the step of de-solvation of the solvated Li⁺ in the liquid electrolyte and the step of transport of Li⁺ in the preformed solid electrolyte interphase (SEI) on electrodes until the Li⁺ accepts an electron at the electrode and becomes a Li in the electrode. Whether the de-solvation process or the Li⁺ transport through the SEI is a limiting step depends on the nature of the interphases at the electrode and electrolyte interfaces. Several examples involving the electrode materials such as graphite, lithium titanate (LTO), lithium iron phosphate (LFP), lithium nickel cobalt aluminum oxide (NCA) and solid Li⁺ conductor such as lithium lanthanum titanate or Li-Al-Ti-phosphate are reviewed and discussed to clarify the conditions at which either the de-solvation or the transport of Li⁺ in SEI is dominating and how the electrolyte components affect the activation energy of Li⁺ charge transfer kinetics. How the electrolyte additives impact the Li⁺ charge transfer kinetics at both the anode and the cathode has been examined at the same time in 3-electrode full cells. The resulting impact on Li⁺ charge transfer resistance, R_ct, and activation energy, E_a, at both electrodes are reported and discussed.

Lithium difluorophosphate (LiDFP) is used as an electrolyte additive to improve the electrochemical performances of LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523)/graphite cells operating at a high charging cutoff voltage. LiDFP additive generates a more uniform, extremely stable, and lower resistance passivation film on the cathode surface. This passivation film not only suppresses the subsequent decomposition of electrolyte, but also prevents the dissolution of transition metal ions from NCM523 particles, resulting in improved cyclic stability and discharge capability of NCM523/graphite cells. With electrolyte contained 1.0 wt% LiDFP, the 18650 batteries achieves a capacity retention of 88.2% after 300 cycles at 3.0∼4.4 V and 90.0% after 200 cycles at 3.0∼4.45 V, comparing to 77.9% and 66.3% of the batteries without additive.

The electrochemical and phase-change behavior of lithium trivanadate during lithiation and delithiation is analyzed by comparing a coupled electrode/crystal-scale mathematical model to operando experiments. The model expands on a previously published crystal-scale model by adding descriptions for electrode-scale resistances. Agreement between simulated and observed electrochemical measurements is compelling. Time and space-resolved operando EDXRD measurements on the cathode are compared with simulated concentration profiles. Both simulation and experiment reveal that during lithiation, phase transformations preferentially occur near the separator, while during delithiation the disappearance of the lithium-rich β-phase occurs uniformly across the electrode.

One of the interests in studying the intercalation phenomenon of Li-ion is to explain the hystereses which are observed on the open circuit voltage curve of the graphite electrode during the charge and discharge. We investigated a potentiometric method to obtain the equilibrium curve and entropy change curve of the graphite electrode in charge and discharge. These curves lead to the analysis of the intercalation compounds in the graphite electrode. The results show a high hysteresis between the lithiation and delithiation in region II on the entropy curve. We do not observe the formation of LiC₁₈ compound which would be observed at filling fraction x = 0.33 and there is no clear evidence of the LiC₂₇ at x = 0.22. Based on our observations, we propose an intercalation model of Li into graphite in an attempt to explain the hysteresis phenomenon which was observed during charge and discharge in region II due to the possible presence of the compound LiC₂₄. We have also observed a possible compound for the LiC₂₄ by XRD post-mortem analysis.

The prevailing electrode fabrication method for lithium-ion battery electrodes includes calendering at high pressures to densify the electrode and promote adhesion to the metal current collector. However, this process increases the tortuosity of the pore network in the primary transport direction and imposes severe tradeoffs between electrode thickness and rate capability. With the aim of understanding the impact of pore tortuosity on electrode kinetics, and enabling cell designs with thicker electrodes and improved cost and energy density, we use here freeze-casting, a shaping technique able to produce low-tortuosity structures using ice crystals as a pore-forming agent, to fabricate LiNi_0.8Co_0.15Al_0.05O₂ (NCA) cathodes with controlled, aligned porosity. Electrode tortuosity is characterized using two complementary methods, X-ray tomography combined with thermal diffusion simulations, and electrochemical transport measurements. The results allow comparison across a wide range of microstructures, and highlight the large impact of a relatively small numerical change in tortuosity on electrode kinetics. Under galvanostatic discharge, optimized microstructures show a three- to fourfold increase in area-specific capacity compared to typical Li-ion composite electrodes. Hybrid pulse power characterization (HPPC) demonstrates improved power capability, while dynamic stress tests (DST) shows that an area-specific area capacity corresponding to 91% of the NCA galvanostatic C/10 capacity could be reached.

A new ageing mode for positive electrode, associated to Ni₂O₃H formation, was observed for the first time in alkaline batteries (Ni-Cd, Ni-MH) during harsh shallow cycling operations. The study of Ni₂O₃H synthesis conditions outlined that γ-NiOOH and βIII-NiOOH phases display instability versus electrolyte at elevated temperature, leading to the irreversible formation of Ni₂O₃H through a reduction, followed by a dissolution / precipitation mechanism. It was shown also that Ni₂O₃H is a rather moderate electronic conductor and is almost electrochemically inactive, in good correlation with the loss of cell capacity. Highlighting NiOOH / Ni₂O₃H transformation provides a new understanding of nickel hydroxide and oxyhydroxide phase transformations diagram.

Layered double hydroxides (LDH) as active electrode materials have become the focus of research in energy storage applications. The manufacturing of excellent electrochemical performance of the LDH electrode is still a challenge. In this paper, the production of CoAl-LDH@Ni(OH)₂ is carried out in two steps, including hydrothermal and electrodeposition techniques. The prominent features of this electrode material are shown in the structural and morphological aspects, and the electrochemical properties are investigated by improving the conductivity and cycle stability. The core of this experimental study is to investigate the properties of the materials by depositing different amounts of nickel hydroxide and changing the loading of the active materials. The experimental results show that the specific capacity is 1810.5F·g⁻¹ at 2 A/g current density and the cycle stability remained at 76% at 30 A g⁻¹ for 3000 cycles. Moreover, a solid-state asymmetric supercapacitor with CoAl-LDH@Ni(OH)₂ as the positive electrode and multi-walled carbon nanotube coated on the nickel foam as the negative electrode delivers high energy density (16.72 Wh kg⁻¹ at the power density of 350.01 W kg⁻¹). This study indicates the advantages of the design and synthesis of layered double hydroxides, a composite with excellent electrochemical properties that has potential applications in energy storage.

Practical lithium-sulfur batteries require high sulfur electrode loading and lean electrolyte designs, which entail more research efforts on the two cell-design parameters - sulfur loading and electrolyte/sulfur loading ratio (E/S). In this work, a systematic investigation is performed to understand the impact of these two variables over key Li-S cell performance parameters. It is demonstrated that Li-S cells' power performance strongly depends on the E/S ratio, while both E/S ratio and sulfur loading significantly influence the cycle life of Li-S cells. Low E/S ratio and high sulfur loading both give rise to fast lithium anode corrosion, which induces fast capacity fade and Coulombic efficiency decay. Pre-passivation of the lithium anode with an ionic conductor Li₃PO₄ protection layer only improves the Coulombic efficiency retention at sulfur loading levels much lower than the practical threshold. Meanwhile, increasing the concentration of LiNO₃ additive in the electrolyte is found effective in sustaining the cycling capacity and the Coulombic efficiency over a reasonable usage window (∼200 cycles). The role of LiNO₃ is the protection of lithium anode during cycling.

3-D nanosheet arrays of Ni₃(VO₄)₂ directly grown on Ni foam through a facile one-step hydrothermal route are used as an electrode for non-enzymatic glucose detection. The structure of Ni₃(VO₄)₂ nanosheet arrays was confirmed by XRD, morphology by electron microscopy and chemical analysis using XPS. In the electrochemical studies, the sensitivity toward glucose sensing of Ni₃(VO₄)₂ nanosheet arrays/Ni foam was compared with bare Ni foam. The studies revealed Ni₃(VO₄)₂ nanosheet arrays/Ni foam exhibited a remarkable high sensitivity of 19.83 mA mM⁻¹ cm⁻² with the response time of ∼1 second and detection limit of 0.57 μM. The amperometric response due to glucose and selectivity toward glucose electro-oxidation was excellent in the presence of interfering reagents such as ascorbic acid, uric acid, dopamine and L-cysteine. Further, the performance of the electrode in flexural conditions and issues such as reusability of the electrode and its application on real samples such as orange juice for glucose sensing have been demonstrated successfully. Overall results validated Ni₃(VO₄)₂ nanosheet arrays/Ni foam electrode as an excellent candidate for glucose sensing, which is binder-free, and possesses high sensitivity and selectivity along with long term stability, good flexibility and reusability.

A novel electrochemical sensor concept, which enables detection of ppb-levels of Pb²⁺ in water, is outlined. The sensor works on the principle of underpotential deposition of Pb onto a Cu electrode followed by measurement of the hydrogen evolution reaction (HER) current on the Pb_upd-modified electrode surface. The degree of suppression of the HER current is correlated to the Pb_upd coverage, which in turn depends on the Pb²⁺ concentration in solution. Feasibility of achieving a detection limit of 10 ppb Pb²⁺ in aerated DI water and tap water is demonstrated and the sensing response time is analyzed using diffusion-reaction calculations.

IrO_x electrodes suffer from large potential drift in solutions in the presence of strong reductive anions such as S²⁻, I⁻, etc. resulting in the inaccuracy of pH measurement. Our homemade IrO_x electrode developed by cycling heat-treatment and quenching process for three times with excellent response property showed the same problem. In-situ/ex-situ XAFS study showed the composition of the IrO_x film changes in strong reductive solution. At the meantime, XPS survey of the IrO_x electrode also verified the composition change of Ir⁴⁺/Ir³⁺ before and after its immersion in these solutions. In order to solve the above problem, the porous-structured IrO_x electrodes were modified by being dipped into Nafion solution for 1∼3 times. Surface and cross section characterizations, EIS tests as well as the pH detection property evaluations were conducted to identify the modification effect and determine a better modification process. Nafion modification for just once is suggested to prevent the electrode from potential drift in solutions containing strong reductive anions. Finally, the pH response mechanism of the modified IrO_x electrode in reductive solutions was discussed.

The evolution of electrochemical biosensors reflects a simplification and enhancement of the transduction pathway. The use of novel conducting polymers in the preparation of sensor platforms has become increasingly studied and imparts many advantages. The sensitivity and overall performance of enzymatic biosensors has improved tremendously as a result of incorporating functional group containing conducting polymers into their fabrication. Hereby, an efficient surface design was investigated by modifying the graphite rod electrode surfaces with conducting polymer displaying functional groups for the immobilization of biomolecules. A model enzyme, glucose oxidase, was efficiently immobilized to the modified surfaces via covalent binding. The biosensor was characterized in terms of its storage and operational stability and kinetic parameters. The designed sensor platform revealed excellent stability and promising kinetic parameters without carbon nanotube or graphene additive. Finally, the sensor platform was tested on beverages for glucose detection.

Herein, a robust novel electrochemical sensor for the detection of prophylactic drug Dimetridazole (DMZ) has been developed eco-friendly through the green synthesis of reduced graphene oxide/Prussian blue microcubes (rGO/PB MCs), and the fabrication was economically done by efficient screen-printed carbon electrode (SPCE) modification method. It is critical as DMZ excess level in poultry farm imposes carcinogenic threats. A responsive, reproducible and long-lasting DMZ sensor was established using the material composed of Prussian blue microcubes encapsulated by thin sheets of reduced graphene oxide (rGO/PB MCs). The rGO/PB MCs composite is prepared through a facile hydrothermal approach, and its elemental, structural, electrochemical and catalyzing abilities are examined. The composite is fabricated on the SPCE, and the resulting improved electrode showed outstanding electrocatalytic ability toward DMZ and the reduction peak current are correlated to the DMZ concentrations. It retains the more extensive working range between 0.02 μM and 1360.1μM and the detection limit reaches 3.2 nM. It also possesses appreciable sensitivity of 2.2935 μAμM⁻¹cm⁻². This technique is efficiently applied to the detection of DMZ in spiked samples of milk and egg.

Nanoporous films of different metal oxides were coated onto a titanium support (sputter coated with platinum or non-sputtered) and submitted to electrochemical impedance spectroscopy (EIS) testing. The arsenic (V) concentration (in an aqueous solution) was varied during the EIS testing to determine how each composite (metal oxide coating + support) would electrochemically respond to arsenic in solution and whether it would be a suitable material for an arsenic (V) sensor electrode. It was found that increasing the amount of metal oxide deposited (film thickness) did not always equate to greater sensitivity for arsenic detection and the support used (sputtered with platinum vs. non-sputtered) also influenced the sensing ability of the composite electrodes. Moreover, factors such as poor repeatability of the fabrication process (acidic SiO₂ sol) and instability of the EIS curves at constant arsenic concentrations occurred with select metal oxide coatings (Fe₂O₃, TiO₂ and Al₂O₃) and would be detrimental to the performance of the sensor. Of the coatings tested, the titanium support sputtered with platinum and coated with ZrO₂ showed the most promise as an arsenic (V) sensor because of the separation and stability of its EIS curves with different arsenic concentrations and the high frequencies for which this occurred.

In this study, non-enzymatic glucose sensors were designed and fabricated by electrochemical deposited platinum nano-crystals, including Platinum nanosphere (Pt NS), Platinum nanorose (Pt NR), and Platinum nanocubes (Pt NC) on fluorine-doped tin oxide glass. The control of the morphologies and growth types was conducted by either potentiostatic or pulse-mode potentiostatic deposition for synthesizing Pt NS, Pt NR, or Pt NC, respectively, at room temperature. Among three Pt nano-crystals, The Pt NC displayed the highest electrocatalytic activity to oxidation of glucose (glucolactone) owning to the single crystalline structure. The developed Pt NC sensor showed a fast response time (2 s), a high sensitivity of 20.75 μA/mM⋅cm, and a detection limit of 0.7 μM (at S/N ratio = 3). By setting glucose oxidation potential to 0.1 V, the Pt NC electrode provided a linear dependence (R² = 0.99086) to glucose in a concentration range from 0.33 to 12.50 mM. The Pt NC electrodes showed stable, highly sensitive, low working oxidation potential, low loading of Pt, and rapid amperometric response in sensing glucose with excellent reproducibility and selectivity, possessing a great potential for non-enzymatic glucose sensing applications.

Chitosan is an amino polysaccharide with possible biomedical applications, for example, in bandage materials or as an antibacterial agent or a cytotoxic agent for tumor and cancer cells. In this study, the cytotoxic effect of chitosan (CTSN-P) on MCF-7 breast cancer cells was monitored in a nondestructive and real-time manner by electrical cell–substrate impedance sensing with a fabricated multidisc indium tin oxide electrode array. The electrical impedance characteristics of cell growth on the multidisc electrode were analyzed by equivalent electric circuit modeling. Application of CTSN-P caused deterioration of viability of cells on the electrode substrate and yielded a CTSN-P concentration–dependent decrease in impedance. The 50% cytotoxicity concentrations in a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and impedimetric assay were 1266.60 and 543.17 μg/mL, respectively. Thus, impedance measurement is suitable for detecting low-dose effects of CTSN-P on the behavior or morphology of live cells.

Nowadays, organic donor-acceptor molecules have attracted a lot of scientific attention because of their unique properties and potential applications in various fields. Although tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) is well known charge transfer salt for a long time, the first application of this material as ion-to-electron transducer in ion-selective electrodes is presented. As a proof of concept, potassium-selective and nitrate-selective solid-state electrodes were constructed. Moreover, TTF-TCNQ intermediate layers were fabricated using two organic solvents. Developed potassium sensors displayed a good Nernstian response with a slope of 58.52 mV/decade (10⁻⁶–10⁻¹ M K⁺), whereas the nitrate-selective electrodes showed a sensitivity of −58.47 mV/decade (10⁻⁵–10⁻¹ M NO^-₃). Reproducible standard potentials and low detection limits were observed. Potential stability of studied electrodes was evaluated using current-reversal chronopotentiometry. The capacitance of TTF-TCNQ-contacted electrodes is 255 μF and 629 μF for K⁺ and NO⁻₃ sensors. The results of measurements conducted reveal that TTF-TCNQ has an appropriate effect on potentiometric sensors performance.

Corrosion of dissimilar friction stir welds (FSW) made in AZ31/AZ80 magnesium alloys was investigated using the scanning reference electrode technique (SRET), and microcapillary polarization technique, complemented by optical and SEM/EDX microscopy. The corrosion rate of the base metals along with the welded specimen was estimated by mass loss testing. The stir zone material in both alloys showed a higher corrosion potential than the base metal due to the partial dissolution of β-Mg₁₇Al₁₂ and Al-Mn particles. The basic corrosion mechanism in dissimilar welds was determined to be different from that of a similar joint. The corrosion behavior of the dissimilar FSW joint was governed by the galvanic coupling of the two alloys, and not by the microstructural evolution occurring during the welding process. The corrosion behavior of the joint was governed by the galvanic coupling between the α-Mg matrix in AZ31 and the Al-rich intermetallics in AZ80. The welded specimens exhibited the highest corrosion rate, while AZ80 was the most corrosion resistant material.

Plasma electrolytic oxidation (PEO) coatings were applied to base metal and dissimilar welded specimens to increase their corrosion resistance. The current density used to produce PEO coatings was found to affect the roughness, thickness and composition of the coating. An applied current density of 20 mA/cm² was found to be a suitable processing condition capable of yielding a uniform coating able to prevent the exposure of the galvanic couple and inhibit its detrimental influence on the corrosion resistance of the dissimilar welded specimen.

Five Fe-33Mn-xC steels, referred to as 0 C, 0.3 C, 0.6 C, 0.8 C, and 1.1 C steels according to their carbon content in mass%, were prepared to clarify the effect of interstitial carbon on the dissolution behavior of steel. The 0.3 C, 0.6 C, 0.8 C, and 1.1 C steels indicated a fully austenitic structure with no carbide precipitate. The lattice parameters of the 0.6 C, 0.8 C, and 1.1 C steels calculated from the γ(111) and γ(200) diffraction peaks increased by up to around 0.8% over that of the 0.3 C steel, suggesting that the added carbon was present as interstitial carbon in the steels. The 0.6 C, 0.8 C, and 1.1 C steels were passivated during the anodic polarization measurements in 0.1 M Na₂SO₄ solution at pH 12.0, whereas the 0 C and 0.3 C steels actively dissolved. The anodic polarization measurements in a buffer solution at pH 10.0 demonstrated a lower dissolution current density for the 0.3 C, 0.6 C, 0.8 C, and 1.1 C steels with higher amounts of interstitial carbon. The dissolution current density at 0.3 V vs. Ag/AgCl (3.33 M KCl) of the 1.1 C steel was reduced to approximately 1 × 10⁻² A m⁻², which was one hundredth that of the 0.3 C steel. The dissolution current density of the steels was not inhibited by the presence of 0.1 M CO₃²⁻ ions, which is an expected dissolution product of interstitial carbon, implying that the interstitial carbon improved the electrochemical property of the steels themselves. The work function of the 1.1 C steel, which showed improved corrosion resistance with interstitial carbon, was 0.12 eV lower than that of the 0 C steel. The peak positions of the Fe 2p_3/2 and Mn 2p_3/2 spectra of the 1.1 C steel indicated the binding energies were approximately 0.1 eV and 0.2 eV higher than those of the 0 C steel. This can likely be attributed to the partial chemical bonding of interstitial carbon to iron and manganese, respectively.

The scanning vibrating electrode technique (SVET) was employed to examine the effect of 'galvanic throwing power' and the distance over which a Mg-rich primer (MgRP) provided sacrificial anode-based cathodic protection to AA2024-T351. Three systems were investigated in full immersion conditions where the same MgRP was used with three different pretreatments: Non-film forming (NFF), trivalent chromium pretreatment (TCP) and anodization with a chromate seal (ACS). Experiments were conducted with two coating/defect area ratios and three parameters were monitored: 1) the maximum peak height of local anodes, inferring the location and intensity of pits, 2) the current density profile at the coating/defect interface (CDI) region and 3) total integrated anodic and cathodic current density values of defined areas in the defect region moving progressively away from the CDI. The NFF-based system was shown to provide the superior galvanic throwing power and a quasi-steady-state galvanic current distribution was detected in the defect region adjacent to the CDI indicating enhanced cathodic activity in response to the MgRP. High resistance between the MgRP and the substrate, due to the thickness of the pretreatment layer, appeared to mediate galvanic interactions in the case of TCP and ACS-based systems.

To elucidate the role of noble metal impurities on corrosion of Mg, 3D time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging in combination with X-ray photoelectron spectroscopy and optical microscopy measurements were carried out on Mg samples (99.9%) before and after Mg polarization at E_OCP+0.5 V in 0.1 M NaCl. A significant segregation of Fe (and of Mn and Al) metallic impurities at grain boundaries (GBs) was observed on the Mg surface by 3D ToF-SIMS. A 3-step mechanism of Mg corrosion was proposed, including a catalytic effect of Fe segregated at the GBs on the hydrogen evolution reaction (HER). In the 1^st stage, the initiation of Mg corrosion is accompanied by the HER occurring over Fe impurities segregated at GBs leading to formation of small circular defects, and propagation with occurrence of dark filiform-like pattern corrosion enriched in Cl⁻. In the 2^nd stage, segregated Fe metallic particles are released by Mg matrix undermining, and are dissolved into Fe²⁺ ions and in the 3^rd stage a redeposition of Fe in the clear areas of Mg surfaces, corresponding to areas with low concentration of Cl⁻, takes place.

This work reports on the application of a rare earth organic compound, praseodymium 4-hydroxycinnamate - Pr(4OHCin)₃, as an effective inhibitor suitable for preventing carbon dioxide corrosion of steels in an aggressive environment. Two steels, namely an AS1020 and a X65 steel, have been tested in 0.01 M NaCl solution saturated with carbon dioxide gas using electrochemical and surface analysis techniques. The results show that X65 steel is less susceptible to corrosion than AS1020 steel in CO₂-saturated 0.01 M NaCl solution as indicated by a lower corrosion current density and a higher polarization resistance. On the other hand, the AS1020 was inhibited much more effectively by praseodymium 4-hydroxycinnamate compound in comparison with X65 steel, as the corrosion behavior of AS1020 and X65 steels was similar in the presence of the inhibitor. However, the inhibiting effects on the anodic reaction was greater for AS1020 due to a reduction in the anodic current density in comparison with X65 steel. The dramatic effect of praseodymium 4-hydroxycinnamate compound could be attributed to the protective inhibiting deposits and enhanced film formation on the more active steel surface.

This study focuses on the elucidation of the formation mechanism of passive layers on AA2024-T3 during the exposure to alkaline lithium carbonate solutions in the presence of sodium chloride. Under controlled conditions, in an electrochemical cell, a protective layer was generated comprising an amorphous inner layer and a crystalline outer-layer. In order to resolve the formation mechanism, the layers were characterized using surface analytical techniques to characterize the surface morphology, thickness and elemental composition of the layers at different stages of the formation process. In addition, electrochemical techniques were applied to link the electrochemical properties of the layers with the different stages of formation. The results demonstrate that the formation mechanism of these layers comprises three different stages: (I) oxide thinning, (II) anodic dissolution and film formation, followed by (III) film growth through a competitive growth-dissolution process. The passive properties of the layers are generated in the third stage through the densification of the amorphous layer. The combined results provide an enhanced insight in the formation mechanism and the development of the passive properties of these layers when lithium salts are used as leaching corrosion inhibitor for coated AA2024-T3.

A systematic study was made to develop the non-chromate and non-fluoride surface treatment for the AZ91 alloy to enable an adherent and corrosion resistant electroless nickel (EN) coating. The performance of the surface treatments is substantiated by the EN coating, in a single and two (duplex) layers on the prior surface pretreated AZ91 alloy, in the subsequent bath. The surface treatment in a solution containing cerium nitrate and subsequent single layer EN coating exhibited good adhesion and an excellent corrosion resistance in 0.5% NaCl solution. The duplex EN layer improved both corrosion as well as adhesion resistance. A remarkable long term (100h exposure) corrosion resistance, assessed using electrochemical impedance spectroscopy (EIS), was shown by the duplex EN coating with an outer layer produced in a bath of pH ∼ 5. In contrast, the duplex coating with an outer EN layer obtained in a bath of pH ∼ 10.5 failed within 4h of exposure. The porosity index of the coating in the order of 10⁻⁶ appears critical for achieving an excellent corrosion resistance. The adhesion resistance, as indicated by the critical load for coating delamination, was successively increased from 5.2 to 10.39N using different pretreatment processes. The adhesion resistance was influenced by the agglomerate particle size and coating thickness.

This study investigated the potential of ceria nanoparticles to reduce the corrosion rates of AA5005 immersed in chloride-rich media at neutral pH. The colloidal ceria nanoparticle dispersion was prepared via precipitation of cerium (III) ions in presence of citric acid. Transmission electron microscopy and dynamic light scattering confirmed the fine structure of ceria; crystallites lower than 10 nm with a hydrodynamic diameter average size of about 30 nm were obtained. Potentiodynamic polarization and electrochemical impedance spectroscopy measurements were conducted on bare AA5005 panels exposed to 0.1 M NaCl with different quantities of ceria nanoparticles. Polarization curves revealed a significant reduction of cathodic current densities for AA5005 immersed in ceria containing electrolytes when compared to the background solution, i.e. a shift toward lower current densities of about one order of magnitude for those containing 5.0 and 7.5% of ceria. Impedance spectra with higher moduli at low frequencies were obtained for AA5005 immersed in ceria containing electrolytes. In general, while in contact to the ceria-containing electrolytes the rates of localized corrosion attacks at the surface of AA5005 were found to decrease and, the outputs from the electrochemical tests suggested an inhibition effect of the colloidal ceria nanoparticles prepared in this work.

Corrosion inhibition of AZ31 Mg alloy with aqueous vanadate was studied and has been attributed to the pH dependence of vanadate speciation. Immersion in tetrahedral coordinated vanadate species, present in neutral and alkaline solution, was shown to decrease corrosion current density and increase the breakdown potential, both of which were enhanced with longer immersion times. Exposure to octahedral coordinated vanadate, predominant in acidic solution, only slightly decreased corrosion current density. An acidic solution was adjusted to alkaline conditions and samples were immersed in the adjusted alkaline solution. Inhibition of these samples was weaker than that of samples immersed in initially alkaline solutions. Anodic inhibition was observed on samples treated in solutions containing tetrahedral species. SEM images showed that vanadate formed a film across secondary particles and the Mg matrix, and provided qualitative evidence that inhibition efficiency increased as the pH increased. XPS results indicated that film formation was associated with the reductive adsorption of vanadium oxoions. Exposure at pH 5.0 produced a film predominated by V⁴⁺. Exposure at pH values of 7.7 and higher, however, produced a film containing predominantly V³⁺. Raman analysis confirmed the formation of a vanadate film on the Mg surface after exposure at all pH values.

Electrochemical methods were used to study the role of Cr(III) on the anti-corrosion behavior of a trivalent chromium process conversion coating on AA2024-T3. The same conversion coating was investigated with and without Cr(III) added to the bath. Polarization curves (naturally-aerated 0.5 M Na₂SO₄ + 0.1% NaCl) revealed similar anodic current suppression by both coatings. Cathodic currents were suppressed more by the coating with Cr(III). Rotating disk voltammetric data revealed that cathodic currents for oxygen reduction were invariant with the rotation rate (rpm)^1/2 for the alloy coated with the Cr(III) conversion coating. The trivalent chromium process coating appears to inhibit oxygen reduction by providing a diffusional barrier and by blocking sites (Cr(OH)₃) for O₂ chemisorption on cathodically-active intermetallics.

Elemental sulfur electrodeposition has not been widely studied due to its usage primarily in compound rather than in elemental form, and also due to its high electrical resistivity. Sulfur thin film electrodeposition is reported here from electrolytes containing 0.10 M Na₂S₄ in dimethyl sulfoxide (DMSO), with either 0.10 M KClO₄ or LiClO₄ as the supporting electrolyte. The high concentration of sulfur precursor S₄²⁻ is obtained by adding Na₂S and S to the electrolyte in a molar ratio of 1:3. Anodic electrodeposition of sulfur onto Au electrodes for 48 hr. at a potential of +0.46 V vs. Ag/Ag⁺ yields a sulfur thin film ∼10 μm thick, which appears to be the thickest sulfur film that has ever been electrodeposited. Elemental analysis by energy dispersive X-ray spectroscopy (EDX) suggests that to within the measurement accuracy, these thin films contain only sulfur. The current density for anodic sulfur electrodeposition is ∼60% higher in LiClO₄- than in KClO₄-containing electrolytes, and a more compact sulfur deposit is obtained. Possible applications of anodic sulfur electrodeposition to metal sulfide deposition are briefly discussed.

In the electrochemical deposition of copper on structured substrates, additives are commonly used as ingredients to refine the copper thin film properties. By means of cyclovoltametric (CV) measurements, we examine the process behavior of the additives PEG (polyethylene glycol) and chloride ions over a wide range of experimental parameters relevant for production-like conditions. In this plating process, additives practically are neither consumed in chemical reactions nor are they incorporated into the growing copper film. To understand the observed complex hysteresis behavior of the deposition current in CV scans, we have recently proposed a model which is able to qualitatively explain this behavior without supposing additive consumption. In the present study, we fit crucial parameters of this model from the experimental data to increase its predictive power. The quantitative agreement of performed simulations of CV scans with the measured scans demonstrates the validity of the proposed copper deposition model. Equipped with the determined parameter set, the model can help to optimize the copper plating process in industrial applications.

The evolution of superconformal Cu electrodeposition in high aspect ratio through silicon vias (TSVs) is examined as a function of polymer suppressor concentration, applied potential and hydrodynamics. Electroanalytical measurements in a CuSO₄-H₂SO₄-Cl electrolyte are used to explore and quantify the effect of such parameters on the metal deposition process. Hysteretic voltammetry due to suppressor breakdown reveals an S-shaped negative differential resistance that leads to non-linear spatial-temporal patterning during metal deposition. For the given hydrodynamic conditions, cyclic voltammetry reveals the potential regime over which positive-feedback gives rise to the superconformal feature filling dynamic. Breakdown of suppression is primarily related to polymer concentrations in the electrolyte while its reformation is dependent on its transport to the interface. Morphological evolution during the early stages of TSV filling reveals two distinct growth front geometries. For dilute polymer concentrations, an initial bifurcation into passive-active surfaces occurs on the side walls of the TSVs followed by bottom-up fill. The depth of the initial sidewall bifurcation within the via increases with polymer concentration. For higher polymer concentrations, i.e. ≥ 25 μmol/L, active metal deposition is rapidly confined to the bottom surface of the via followed by sustained bottom-up filling.

The effect of a cationic dispersant, polyethyleneimine (PEI) on electrodeposition of nickel/titanium carbide (Ni/TiC) nanocomposites is characterized. Enhancing the dispersion of TiC nanoparticles in the electrolyte and increasing TiC amount and uniformity in the deposit are crucial to get superior mechanical and tribological nanocomposite properties. Therefore, a key challenge in reaching enhanced composites is the optimization of the dispersant concentration that improves the nanoparticle dispersion in the electrolyte and achieves high and uniform TiC incorporation into the deposit without suppressing electrodeposition. It is determined that PEI at a concentration of 125 ppm increases the stability of TiC nanoparticles in the electrolyte and TiC vol% in the deposit significantly without any substantial inhibition on the electrodeposition kinetics. Ni/TiC electrodeposition is also characterized as a function of key parameters such as TiC electrolyte concentration, current density, and rotation speed in the presence of PEI. Higher and more uniform TiC nanoparticle incorporation is attained for the electrolyte containing PEI than the electrolyte with no dispersant for all cases. Uniform nanocomposites with improved hardness is obtained as a result of Ni/TiC electrodeposition in the presence of the cationic dispersant.

Two highly ordered porous Al scaffolds were synthesized by applying a soft template assisted electrodeposition method, using an ionic liquid as the electrolyte. Polystyrene (PS) spheres with an average diameter of 399 ± 2 nm or 89 ± 20 nm were deposited on a polished Cu electrode using a dip-coater. An imidazolium-based ionic liquid mixed with aluminium chloride [EMIm]/AlCl₃ (40/60 mol%) was used as the electrolyte for the Al electrodeposition. The PS spheres that were used as a soft template were removed after the Al electrodeposition method by chemically dissolving them in tetrahydrofuran (THF). Lithium borohydride (LiBH₄) was then melt-infiltrated into the porous Al scaffold. Morphological observations of the dip-coated Cu electrodes with the PS spheres, the as-synthesized porous Al scaffolds, and the LiBH₄ melt-infiltrated samples were carried out using Scanning Electron Microscopy (SEM). The scaffolds exhibited a highly ordered porous Al structure with an open network of pores and an average pore size of 355 ± 25 and 56 ± 20 nm respectively. The porous Al acts as a reactive scaffold which interacts with LiBH₄ at elevated temperature. Temperature Programmed Desorption (TPD) experiments revealed that the melt-infiltrated LiBH₄ samples exhibited faster H₂ desorption kinetics in comparison to the bulk material. In particular, the 56 ± 20 nm Al scaffold showed a H₂ desorption onset temperature (T_des) at 100°C which is 250°C lower than for bulk LiBH₄. This temperature drop can be attributed to the size reduction of LiBH₄ down to the nanoscale, together with the high contact surface area with the Al scaffold.

We propose here a facile electrodeposition method that is assisted by N, N-Dimethylformamide (DMF) selective coordination with Pt ions, and succeed in synthesizing highly active PtCo alloy catalysts for the oxygen reduction reaction (ORR). It is very ingenious that DMF is selectively coordinated with Pt ions, thus greatly bridging the deposition potential gap between Pt and Co, and promoting the formation of alloy catalysts. The optimal Pt₄Co alloy sample exhibits a remarkable specific activity as high as 1.52 mA·cm⁻²_Pt at 0.9 V (vs. RHE) towards the ORR, 7 times of that for the commercial Pt/C catalyst. It is believed that the remarkable ORR electrocatalytic activity is mainly ascribed to the synergetic effect from two aspects dealing with a DMF selective coordination with Pt ions as well as the generation of highly porous Pt-rich surfaces.

Electrodeposition of tin-bismuth alloys on polycrystalline copper electrodes has been studied from an acidic bath comprising SnCl₄, Bi(NO₃)₃, citric acid, poly(vinyl alcohol) and betaine. Using linear sweep voltammetry (LSV) and chronoamperometry (CA), co-deposition of tin and bismuth from the above bath has been examined. Bismuth (III) ions get reduced in a single-step, three-electron-transfer reaction while tin (IV) ions undergo a two-step reduction through the formation of tin (II) ions. Nitric acid in the bath not only enhances solubility of the precursors but also decreases the peak potential separation between bismuth (III) and tin (II) ions. Through the introduction of various additives and variation in bath pH, co-deposition is preserved while the composition of tin in the obtained alloy is modified. The morphologies, composition and crystallinity of the deposits have been determined using scanning electron microscopy, inductively coupled plasma atomic emission spectroscopy and X-ray diffraction, respectively. A wide range of alloy compositions (from 14% to 75% tin), including the eutectic Sn-Bi alloy have been deposited. Novel morphologies such as yarns-of-spool have been obtained.

Influences of pulse plating parameters on chemical composition, grain size, morphology, and mechanical property of Au–Cu alloy films electrodeposited with an Au-rich sulfite-based electrolyte were investigated. A wide range of Cu concentration (w_Cu) varied from 3.5 to 26.7 wt% was attained in the Au–Cu films. The galvanic displacement reaction occurred during the off-time period showed great influences on the composition and the grain size. Meanwhile, surface morphology of the Au–Cu films was interrelated with the alloy composition. An increase in the pulsed current density lead to roughening of the surface, and smoothening of the surface was achieved by promoting the displacement reaction. Micro-mechanical properties of the Au–Cu films were evaluated by micro-compression tests for applications as movable micro-components in electronic devices. A pronounced high yield strength at 1.38 GPa was achieved in the Au–Cu film with the smallest grain size at ca. 4.40 nm and the w_Cu at ca. 15 wt%, which is suggested to be a result of synergetic effects of grain boundary strengthening and solid solution strengthening mechanisms.

In this work, Raman measurements were performed with quenched LiCl-KCl-LiF-ZrCl₄/ZrF₄/K₂ZrF₆ salt mixtures for deciphering the coordination chemistry of zirconium(IV) in the presence of fluoride ion in the melt. The occurrence of ZrCl₆²⁻, ZrCl₄F₂²⁻, ZrF₆²⁻, ZrF₇³⁻ and ZrF₈⁴⁻ in melt at different F/Zr molar ratios was confirmed by Raman spectra. The electrochemical redox behaviors of zirconium in LiCl-KCl-LiF-ZrCl₄ were also examined at 773 K. Transient methods such as cyclic voltammetry and square wave voltammetry were used. In LiCl-KCl-LiF-ZrCl₄ with LiF concentration less than 1.27 wt% (molar ratio F/Zr < 9.1), the reduction behavior was found to be largely dependent on the formed Zr(I) species; In LiCl-KCl-8.0 wt% LiF (F/Zr > 101), the reduction of Zr(IV) followed a two-step mechanism of Zr(IV)/Zr(III) and Zr(III)/Zr(0) at the potentials of about −0.85 and −1.40 V versus Pt, respectively.

Alumina-silica embedded zinc coatings with an enhanced protective performance for sintered NdFeB magnet were prepared using electro-deposition method from a mixture of alumina-silica sol (ASS) and zinc plating solution. The zinc-ASS coatings have been fabricated with various ASS concentrations in sol contained plating baths (SCPB). According to electrochemical results, the positively charged ASS particles adsorbed on cathode and deposited with the electro-deposition of zinc coatings. The influence of the ASS concentration in SCPBs on the deposited coating structure, composition and growth mechanism were investigated. With the increase of ASS concentration, more ASS particles got adsorbed on cathode surface during the deposition process, which affected the crystal structure and composition of the deposited zinc coatings. Among the prepared samples, ASS embedded zinc coating exhibited relatively good wetting behavior, adhesive and wear properties, which should be attributed to the adsorption and incorporation of ASS particles. The corrosion current density of 10%-SCPB prepared zinc coating was more than an order of magnitude lower than the sol free zinc coating. This kind of approach was helpful to fabricate zinc-ASS coatings with enhanced mechanical and anti-corrosion properties for NdFeB magnets.

The low or even negligible solubility of most metal chlorides in the imide-type ionic liquids (ILs), such as 1-n-butyl-1-methylpyrrolidinium bis((trifluoromethyl)sulfonyl)imide ([BMP][TFSI]) used here, sometimes brought inconvenience to the electrodeposition in this type of ILs. In this study, it has been demonstrated that NiCl₂ and ZnCl₂ can be used as the metal sources for the electrodeposition of Zn-Ni alloys in [BMP][TFSI]. ZnCl₂ is inherently soluble in [BMP][TFSI] but two equivalents of [BMP][Cl] are needed to make NiCl₂ dissolve. More than two equivalents of [BMP][Cl] relative to the total molar numbers of NiCl₂ plus ZnCl₂, however, are needed for preparing the electrodepositing baths of Zn-Ni alloys. The ZnCl₂/NiCl₂/[BMP][Cl] baths are more stable than that prepared by the dissolution of Ni(TFSI)₂ and ZnCl₂ because, in the latter solution, NiCl₂ precipitates gradually due to the reaction between Ni²⁺ and the Cl⁻ from ZnCl₂. Potentiostatic electrodeposition was conducted to deposit Zn-Ni alloys on copper substrates, and amorphous Zn-Ni alloys were obtained.

The electrochemical reduction of Al₂O₃ has been investigated in molten CaCl₂ at 1123 K. To predict the electrochemical reduction behavior depending on the activity of O²⁻ ions, the potential–pO²⁻ diagram for the Al–Ca–O–Cl system is constructed from thermochemical data. In a Mo box-type electrode, an Al₂O₃ tube is successfully reduced to liquid Al with a maximum purity of 98 at%. However, in the electrolysis of Al₂O₃ powder in an Fe box-type electrode, Al₂Ca is produced through the formation of Ca₁₂Al₁₄O₃₃ as an intermediate product. The different electrochemical reduction behaviors of the tube and the powder are explained by the different diffusion path lengths for O²⁻ ions from three-phase zone (Al₂O₃/CaCl₂/cathode metal) to bulk CaCl₂.

The electrowinning of nuclear-grade Zr from a Ba₂ZrF₈–ZrF₄ salt system at 780°C was investigated by using a zirconium tube and a copper plate as cathode materials. An equimolar Ba₂ZrF₈+ ZrF₄ mixture was used as a low-melting-point electrolyte. Here, Ba₂ZrF₈ is a single source of zirconium and ZrF₄ is an auxiliary product to convert Ba₂ZrF₈ into a low-melting-temperature BaZrF₆ salt (T_melt = 730°C). The cyclic voltammetry measurement indicated that the reduction of Zr⁴⁺ ions has a two-step character corresponding to the Zr⁴⁺/Zr²⁺ and Zr²⁺/^Zr0 transitions. The electrochemical reduction behavior of Zr ions on the zirconium tube (inert cathode) and the copper plate (reactive cathode) was analyzed in terms of deposition time and the phase composition of the deposited layers. The metal deposit obtained on the Zr electrode was a single-phase Zr metal, whereas on the Cu electrode, two layers consisting of Cu–Zr and Zr phases were revealed. The further melting of the as-prepared Zr deposit yielded a nuclear-grade Zr ingot with 99.99% purity.

The effect of chromium(VI) on the kinetics of disproportionation of hypochlorous acid and hypochlorite was established in the solution for the electrolytic production of chlorate. The hexavalent chromium species Cr₂O₇²⁻, HCrO₄⁻ and CrO₄²⁻present in the solution catalyze the disproportionation reaction. In both the absence and presence of chromium(VI), disproportionation is a third-order reaction with respect to HClO and ClO⁻, and a first-order reaction with respect to the hexavalent chromium species. In the presence of chromium(VI) ions, four parallel reactions probably take place in the solution i.e. uncatalyzed disproportionation and three parallel reactions catalyzed by Cr₂O₇²⁻, HCrO₄⁻ and CrO₄²⁻ions. Most likely, the hexavalent chromium species do not change the sequence of elementary reactions in the disproportionation mechanism but only speed up the rate-determining step through interaction with its reactants. In the chlorate production process, as chromium(VI) concentration increases, the optimum pH which ensures the maximum rate of disproportionation is shifted to an acid environment. This is due to an increase in the concentration of the catalytically most active species HCrO₄⁻ with increasing acidity of the solution. A mathematical model of the kinetics of the chromium(VI)-catalyzed disproportionation of hypochlorite and hypochlorous acid into chlorate was set up. Good agreement was obtained between theoretical and experimental data.

MnO_x/Ti composite membranes, MnO_x coated on the original porous Ti support membrane, were synthesized by sol-gel method. The effect of heat-treatment temperature (220-380°C) on the crystal structure of nano-MnO_x was investigated by XRD, FESEM and XPS. The XRD results showed that crystal gain size increased with the rise of heat-treatment temperature, and at the temperature of 220 to 300°C, the crystal structure was mainly Mn₃O₄, which transformed to Mn₃O₄ and α-Mn₂O₃ mixed crystal after 300°C. Electrocatalytic membrane reactor (ECMR) assembled with MnO_x/Ti composite membrane as an anode and a stainless steel mesh as a cathode was employed for phenolic wastewater treatment. The phenol, COD and TOC removal rate of ECMR with MnO_x/Ti heat-treated at 220°C reached the maximum value of 93.09%, 79.25% and 68.54%, whereas were 54.85%, 40.25% and 35.10% in case of the original Ti membrane as the anode, respectively. The sequence of catalytic activity was as follows: Mn₃O₄ > Mn₂O₃, which was also correlated with the grain size of the catalyst. The higher phenol removal obtained were related to the synergistic effect of the electrochemical oxidation and separation in ECMR, whose MnO_x as catalysts also played a key role on the electrocatalytic oxidation of the phenolic wastewater.

Effects of the KF-NaF-AlF₃ melt composition, ZrO₂ concentration and aluminothermic synthesis parameters on the conversion rate of zirconium to aluminum were investigated. The kinetics of zirconium electroreduction on glassy-carbon obtained from KF-AlF₃-ZrO₂ melts at a temperature of 750°C was studied via the cyclic voltammetry method. Parameters of the electrolysis of KF-NaF-AlF₃-ZrO₂ melts were derived on the basis of obtained results, and the theoretical possibility for the electrolytic production of Al-Zr master alloys (having up to 15 wt% zirconium content) was demonstrated.

Newly developed wire electrochemical machining (WECM) operates in the same principle of electrochemical machining (ECM) and has recently been very popular for fabrication of different microfeatures effectively. However, the capability and possibility of this newer process is still out of limelight and require specific and extensive research to explore. Hence, the present research work deals with indigenous development of suitable WECM setup for fabricating microslits with feed values as high as that employed during wire electrical discharge machining (WEDM) process, thereby making WECM a cost effective technique for batch scale production. The influence of applied voltage and duty ratio on maximum feed has been investigated and mathematical modeling for finding out a correlation between maximum feed with values of voltage and duty ratio has been developed and validated. Moreover, maximum feed achieved with different parameter settings has been tabulated. It has been found that maximum feed that can be achieved during controlled machining with 18 V, 18% duty ratio, 50 kHz frequency and 0.1 M H₂SO₄ is 0.84375 mm/min which can still be compared with feed rates commonly employed during WEDM, given the fact that tungsten wire of diameter as low as 50 μm has been used in the present study.

Lamellar Ni₃Si microchannels and Ni₃Si micropore arrays were fabricated in directionally solidified Ni–Ni₃Si hypereutectic alloys by selective dissolution. Regular lamellar and rod-like structures were obtained at growth rates of 1–6 μm/s for the hypereutectic alloys. The dissolution of the lamellar or rod-like Ni phases while passivating the continuous Ni₃Si matrix resulted in continuous microchannels or nanopore arrays in the Ni–Ni₃Si hypereutectic alloys. During selective dissolution, SiO₂ preferentially formed on the Ni₃Si phase and retarded its dissolution. The width of the microchannel was 2.85 μm, and the micropore diameter was approximately 7.86 μm. The structural materials with narrow microchannels can be applied in the field of catalyst, microfiltration, and micro/nanostructure fabrication.

Cu nanoparticles were synthesized via electrochemical deposition and the effect of the addition of poly(N-vinyl-pyrrolidone) (PVP) and pH on the properties of the nanoparticles was investigated. The Cu nanoparticles were prepared from an electrolyte containing copper acetate (pH 5.50) or copper sulfate (pH 4.14) by collecting the dispersed particles in the solution after electrochemical reduction. With the use of the acetate bath, formation of Cu₂O at −0.2 and −1.5 V vs. Ag/AgCl was confirmed. On the other hand, Cu₂O formation was not observed with the sulfate bath due to the lower pH, and the Cu nanoparticles could not be obtained at the potential of −1.5 V vs. Ag/AgCl. Surface enhanced Raman spectroscopy with plasmon sensors was used to investigate the transformations of PVP during electrolysis under the different conditions when Cu particles were and were not formed. For the dispersed nanoparticles in the electrolyte, it was observed that the C=O and C–N peaks of PVP also exhibited a red-shift. It was thus confirmed that PVP was coordinated to both the cathode electrode and dispersed nanoparticles in the electrolyte upon electrochemical reduction.

Core-shell Fe₃O₄@C@MnO₂ microspheres were fabricated using multi-step solution-phase interface deposition. Fe₃O₄ nanoparticles were coated with SiO₂ via the Stöber method and further covered with resorcinol and formaldehyde (RF) resins. Fe₃O₄@C nanoparticles with inter-lamellar void were obtained by carbonizing RF under N₂, and etching SiO₂ with NaOH. These nanoparticles served as template and were further coated with MnO₂ shell to prepare Fe₃O₄@C@MnO₂ microspheres. The resultant composites showed a typical core-shell structure with distinct magnetite core, 10 nm inter-lamellar void, a 30 nm thick carbon layer in the middle layer, and a 50 nm thick MnO₂ shell at the outer layer. Fe₃O₄@C@MnO₂ microspheres served as supercapacitor electrode materials. The electrochemical performance of the Fe₃O₄@C@MnO₂ electrode was investigated using cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge. Fe₃O₄@C@MnO₂ electrode showed a specific capacitance of 158 F g⁻¹ at 0.5 A g⁻¹ and outstanding cycle stability with 89.7% capacitance retention after 2000 cycles. By contrast, the specific capacitance of Fe₃O₄@C electrode was 117 F g⁻¹ at 0.5 A g⁻¹ exhibited and only 75.2% capacitance retention after 2000 cycles. Thus, Fe₃O₄@C@MnO₂ microspheres had great potential in supercapacitor applications in the future.

A new plasma-assisted electrolysis method has been developed to synthesize amorphous TiO₂ nanoparticles and exploited for the enhanced photocatalytic performance. The method is simple, environmentally friendly, produces nanoparticles directly from bulk metal, and is suitable for mass production. The process was conducted in low-concentration nitric acid electrolyte under a voltage of 450 V, the minimum necessary to produce plasma on the anode surface. The average nanoparticle size was tuned between 16 and 28 nm by controlling electrolyte concentration within the range of 5 to 15 mM. The production rate increased with time, with the maximum of 11.27 g/h. The amorphous TiO₂ nanoparticles were calcined at various temperatures to determine the crystalline structures and to compare their photocatalytic effects. The structure ranged from pure anatase to rutile under various calcination temperatures; the anatase–rutile mixed phase produced at 600°C showed the highest catalytic performance, with 94% degradation of methylene blue within 30 min owing to a synergetic effect between the phases. This liquid-phase plasma-assisted electrolysis method can pave the way for large-scale synthesis of highly pure metal-based ceramic nanoparticles with narrow size distributions.

A smooth and flat uranium surface with trace of well-defined grain boundaries has been obtained by electropolishing in the Lewis acidic AlCl₃-1-ethyl-3-methylimidazolium chloride ionic liquid. The surface roughness Ra and Ry of the uranium reduced substantially from 130.1 nm and 899.4 nm to 16.77 nm and 206.89 nm after electropolishing, respectively. The underlying mechanism of electropolishing has been investigated by the combination of electrochemical, spectroscopic and surface characterization methods. A current density plateau in the measured polarization curves of uranium is observed, which is directly related to the mass transport limit of U³⁺. The mass transport mechanism of the process follows the salt precipitation model, and the precipitate is proposed to be in the form of U(Al₂Cl₇)_x(AlCl₄)_3-x.

In this work, we performed EME experiments under a constant direct electric current with PIM. The method not only offered working opportunities with very low potential values (50–70 V), but also highlighted the suitability of PIM applications under constant current in EME. The donor solution is containing the target analyte while in the right chamber there is an acceptor solution to transport the target analyte. Cr(VI) transported from sample solution to an acceptor solution with a high efficiency and recovery 99.75% in 50 minutes. We worked applied electric current constant, platinum wire thickness, membrane stability and life through EME-PIM process, selectivity and applicability of EME-PIM process to the real samples. The Scanning Electron Microscopy also used to elucidate the morphology and structure of PIMs. The membrane's stability and the EME's reproducibility greatly improved by using a constant electric current instead of constant voltage, which can further lower transport times and enhance economical aspects of large-scale applications.

This work presents numerical simulations, with validation considering analytical expressions and experimental results, of mass-transfer in electrochemical reactors under laminar and turbulent flows in ducts of rectangular and tubular shape. Sudden expansion at the reactor inlet and segmented electrodes are also analyzed. Computational fluid dynamics (CFD) simulations were performed solving the laminar or RANS equations with the Shear Stress Transport (SST) k-ω turbulence model using the open source code OpenFOAM in steady-state. For mass-transfer simulations, the averaged diffusion-convection equation was implemented and solved. A good agreement between mass-transfer simulations with experimental data and analytical results were attained for both laminar and turbulent flow. Discussions about the segmented electrode technique in order to obtain local mass-transfer data in laminar and turbulent flow are also performed.

A series of mesoporous TiO₂ (MT) materials were synthesized by a hydrothermal procedure using Cetyltrimethyl ammonium bromide (CTAB) and Poly (ethylene-glycol)-block-poly (propylene-glycol)-block-poly(ethylene-glycol) (P123) as templates, and titanium tetrachloride as a titanium source. The molar ratios of Ti/CTAB and Ti/P123 were optimized via Brunauer-Emmett-Teller (BET) measurement. MT materials made with the two templates formed rutile and anatase crystal phases as indicated by X-ray diffraction (XRD) and laser Raman spectrometry (LRS). Scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) characterization indicate that the anatase MT material formed by P123 template shows immense potential as photoanode in dye sensitized solar cell (DSSC) devices. The analysis of current to voltage (J-V) curves and electrochemical impedance spectroscopy (EIS) corroborated the previous characterizations and the highest power conversion efficiency (PCE) of the cells involving MT using P123 with a Ti/P123 molar ratio of 13:1 as the templates reached 8.12%, which is much higher than that with CTAB (5.43%) as a template and commercial P25 (5.15%) based devices.

Polymer electrolyte fuel cells' (PEFCs) widespread commercialization is hindered by the devices' limited durability, in terms caused by the corrosion of the carbon support used in the Pt-based PEFC catalysts. Using unsupported electrocatalysts could mitigate such durability issues, but little is known regarding the manner in which their processing into catalyst layers (CLs) affects pore size distribution (PSD) and PEFC performance. Thus, we have used a computational model to investigate the modes of agglomerate packing in CLs made from unsupported Pt₃Ni nanochain ensembles (aerogels) or Pt black, and complemented this analysis with focused ion beam scanning electron microscopy tomography of corresponding real CLs. 3D structures, PSDs and tortuosities were obtained for real and computed CLs and were found to be in good agreement. The Pt black CL mainly exhibits large and straight pores (>100 nm wide), while the Pt₃Ni aerogel CL mostly features small and twisted pores (< 100 nm wide) that cause the significantly poorer O₂ mass transport (vs. Pt black) observed in PEFC experiments. Moreover, this modeling approach leads to key insights on the working principle of a filler material used for positively shifting the average PSD and improving the PEFC performance of the Pt₃Ni CL.

In this work, the symmetrical solid oxide electrolysis cell (SOEC) with the configuration of La_0.6Sr_0.4Fe_0.8Ni_0.2O_3-δ (LSFN)-GDC/GDC/YSZ/GDC/LSFN-GDC is evaluated with electrochemical performance for direct electrolysis of pure CO₂. The results find that the current density increases from 1.03 A/cm² at 800°C to 1.52 A/cm² at 850°C under an electrolysis voltage of 2.0 V and the polarization resistance (R_p) is as low as 0.12 Ω·cm² at 800°C. The formation rates of CO can reach 5.16 and 6.35 mL/min·cm² at the voltages of 1.8 and 2.0 V at 800°C, respectively. Furthermore, the cell also displays good stability in the short-term CO₂ electrolysis test. The research confirms that this novel LSFN is a potential electrode material in symmetrical solid oxide electrolysis cell for pure CO₂ electrolysis.

Cobalt phthalocyanine (CoPc) is supported on homemade three-dimensional graphene (3D-G) to prepare CoPc/3D-G catalysts used for oxygen reduction reaction (ORR). 3D-G is made from coal tar pitch with nano MgO as template and KOH as activation agent. Raman spectra indicate that 3D-G is multi-layered. Transmission electron microscopy images show that CoPc/3D-G retains the mesoporous foam structure of 3D-G and CoPc is dispersed homogeneously on the surface of 3D-G. CoPc/3D-G shows a half-wave potential of 0.85 V vs. RHE in oxygen-saturated solution of 0.1 M KOH, which is 50 mV higher than that of 6 wt% Pt/C. The electron transfer number of CoPc/3D-G is 3.99 at 0.65 V vs. RHE, indicating that oxygen reduction is catalyzed mainly via a four-electron process. CoPc/3D-G exhibits a current density loss of 10% after 40,000 s in chronoamperometry tests, while CoPc/C lost 17.5% after the same period.

A long-term test with a two-layer solid oxide cell stack was carried out for more than 20,000 hours. The stack was mainly characterized in a furnace environment in electrolysis mode, with 50% humidification of H₂ at 800°C. The endothermic operation was carried out with a current density of −0.5 Acm⁻² and steam conversion rate of 50%. Electrolysis at lower temperatures (i.e., 700°C and 750°C) and fuel cell operation (with 0.5 Acm⁻² and fuel utilization of 50%) at 800°C were also carried out (<2000 h each) for comparison. The voltage and area specific resistance degradation rates were ∼0.6%/kh and 8.2%/kh after ∼18,460 hours of operation. In total, the stack was operated above 700°C for more than 20,000 hours. Impedance measurement and analysis showed that the increase of ohmic resistance was the main degradation phenomenon, while electrode polarizations were kept nearly constant before a severe burning took place in one layer. Ni-depletion in fuel electrodes was confirmed during post-mortem analysis, which was assumed to be the major degradation mechanism observed. The stack performance and degradation analysis under different working conditions, as well as the results of preliminary post-mortem analysis will be presented.

Solid oxide fuel cell (SOFC) electrode materials with surface areas up to 99 m²·g⁻¹ were prepared at traditional sintering temperatures, 1050°C–1350°C, by sintering hybrid inorganic-organic materials in an inert atmosphere followed by calcination in air at 700°C. The electrode materials investigated were yttria-stabilized zirconia (YSZ), lanthanum strontium cobalt ferrite (LSCF), gadolinia doped ceria (GDC), and strontium titanate (STO). During sintering, an amorphous carbon template forms in situ and remains throughout the sintering process, aiding in the creation and preservation of mixed-metal-oxide nanomorphology. The carbon template is removed during subsequent calcination in air at 700°C, leaving behind a nanostructured ceramic. Phase stability, carbon template concentration, and specific surface area was determined for each mixed-metal-oxide. Final specific surface areas up to 83, 66, 95, and 99 m²·g⁻¹ were achieved for YSZ, LSCF, GDC, and STO, respectively. The impact of high surface area YSZ on symmetrical YSZ-lanthanum strontium ferrite (LSF) cathode cell performance was evaluated in the temperature range of 550°C–800°C. Adding nanostructured YSZ decreased the electrochemical impedance by 45% at 550°C. The performance improvement lessened with increasing temperature, and at 800°C there was essentially no improvement. The findings reveal a promising approach to improving low temperature SOFC performance.

The morphological change in nickel (Ni) caused by coarsening during a high temperature operation has been considered one of the main reasons for the performance degradation of conventional composite Ni-yttria stabilized zirconia (Ni-YSZ) solid oxide fuel cell (SOFC) anodes. An improved phase field model is proposed to simulate the Ni coarsening in a Ni-YSZ anode with both the Ni volumetric morphology and multiple crystallographic orientations evolved. Using a three-dimensional (3D) reconstruction of the initial anode microstructure obtained based on focused ion beam-scanning electron microscopy (FIB-SEM), the time dependent evolutions of triple phase boundary (TPB) density, specific Ni surface and Ni-YSZ interface areas, the volume fraction of isolated Ni, and the other factors can be quantitatively analyzed. To validate the model, it was tested based on different initial microstructures from the same anode. Multiple factors that may influence the anode durability during a long-term operation were quantitatively investigated based on the model.

Due to the time required to test fuel cell degradation experimentally, a physics-based model which can predict degradation can be a valuable tool. Grain coarsening and the resulting microstructure evolution is a primary mode of degradation. In this study, a multi-physics model of a fuel cell is presented which can predict performance loss as a function of time caused by coarsening in the electrodes of an LSM-YSZ/YSZ/Ni-YSZ SOFC. Microstructural properties are updated as a function of time from their initial values using functional relations derived from experimental data. Specie and charge transport equations are solved to predict performance changes with time from the microstructural changes. The model is first calibrated such that it correctly captures the performance of a button cell. Performance change over time predicted by the model is compared to experimental data for a cell operated for 775 hours. It is found that the model predicts a slower degradation rate than the rate which occurs experimentally. This is reasonable as other forms of degradation are not being accounted for. The model is then used to make long term predictions of cell performance loss due to grain coarsening out to 40,000 hours for various operating temperatures and initial microstructures.

A highly active and stable bifunctional electrocatalyst for oxygen evolution reaction (OER) and hydrogen evolutionreaction (HER) in alkaline media based on Ni-doped Mo₂C-MoN particles supported on porous N-doped graphitic carbon is studied in this work. The optimized Mo₂C-MoN/Ni@NC catalyst shows small over potential of 296 mV and 183 mV at 10 mA cm⁻² on glassy carbon electrode for OER and HER, respectively. The best catalyst is the mixture of hexagonal Mo₂C, MoN and metallic Ni. The high catalytic performance is explained by the synergistic effect between metallic Ni and Mo compounds. The promotion effect of Ni to Mo₂C-MoN leads to high OER activity and Mo₂C is crucial for HER. The good stability and easily scale-up make the Mo₂C-MoN/Ni@NC a promising bifunctional catalyst for water splitting in alkaline media.

One of the primary challenges for proton exchange membrane (PEM) electrolyzers is the sluggish kinetics of the oxygen evolution reaction (OER) at the anode, which requires the use of precious metals or metal oxides, such as iridium (Ir) or iridium oxide (IrO_x), as the OER catalyst. This study introduces a one-pot surfactant-free polyol reduction method to disperse iridium nanoparticles on a tungsten doped titanium oxide (W_xTi_1-xO₂) support. The polyol reduction approach for the Ir/W_xTi_1-xO₂ catalyst synthesis was systematically investigated to determine the influence of synthesis parameters on the catalysts' physical properties, and its electrochemical activity and durability. The most promising synthesized catalyst with 38 wt% Ir (Ir_38%/W_xTi_1-xO₂) demonstrated five times higher mass activity than an Ir-black baseline (the industry standard catalyst) based on rotating-disk electrode (RDE) studies. When tested in a real water electrolyzer system, the synthesized catalyst enabled the Ir loading to be lowered by an order of magnitude while retaining a similar electrolyzer performance found for the baseline Ir-black catalyst. The Ir_38%/W_xTi_1-xO₂ catalyst also demonstrated remarkable stability, e.g., only small voltage (<20 mV) increase was observed during a 1200-hour durability test at a constant current density of 1500 mA/cm².

For use of metal supported solid oxide fuel cell (MS-SOFC) in mobile applications it is important to reduce the thermal mass to enable fast startup, increase stack power density in terms of weight and volume and reduce costs. In the present study, we report on the effect of reducing the Technical University of Denmark (DTU) SoA MS-SOFCs support layer thickness from 313 μm gradually to 108 μm. The support layer thickness decrease in the DTU co-sintering MS-SOFC fabrication route results in an increased densification of the support layer and a slight decrease in performance. To mitigate the performance loss, two different routes for increasing the porosity of the support layer and thus performance were explored. The first route is the introduction of gas channels by puncturing of the green tape casted support layer. The second route is modification of the co-sintering profile. In summary, the cell thickness and thus weight and volume was reduced and the cell power density at 0.7 V at 700°C was increased by 46% to 1.01 Wcm⁻² at a fuel utilization of 48%. All modifications were performed on a stack technological relevant cell size of 12 cm × 12 cm.

In our previous study copper oxide additions were used to accelerate the formation of perovskite LaFeO₃ conversion coatings on stainless steels from molten carbonate baths. Incorporation of copper particles into the growing coating was an additional effect resulting in the formation of a composite Cu-LaFeO₃ structure. In continuation to our previous study, the aim of this work is to report the effect of copper additions on long-term stability and performance of perovskite conversion coatings under IT-SOFC interconnect conditions. To this end, a Cu-LaFeO₃ coated K41 18Cr ferritic stainless steel was examined in air at 700°C up to 1000 h. In order to simulate properly the situation of a real IT-SOFC cell, Area Specific Resistance (ASR) and Cr-barrier properties of the coated steel were evaluated simultaneously with a special coating characterization setup. Studies were conducted by comparison with single-phase LaFeO₃ coatings obtained in a molten carbonate bath similar to that used for the formation of the composite Cu-LaFeO₃ coatings but without the addition of copper oxide. Copper addition did not change the general morphology of the perovskite coating, which remains a multi-layer coating, being composed of an outer LaFeO₃ crystalline layer, a middle Fe-rich oxide and two inner Fe-Cr rich oxide layers. However, copper was beneficial in promoting a thinner and more stable coating structure along with finer perovskite grain size. These structural improvements were further confirmed by the results obtained with electrical measurements that showed a better ASR behavior of the Cu-LaFeO₃ coatings. On the other hand, no relevant copper effects could be detected on the coating oxidation stability and on the Cr-barrier properties of the perovskite conversion coatings. Both LaFeO₃ and Cu-LaFeO₃ coatings showed similarly high coating stability and excellent Cr-barrier capability in experiments conducted at 700°C up to 1000 h. In definitive, dual-phase Cu-LaFeO₃ seem more promising systems for IT-SOFC interconnects than single-phase LaFeO₃ conversion coatings, although further improvements in ASR electrical properties are needed.

A 3D model is developed by coupling the equations for momentum, gas-phase species, heat, electron and ion transport to analyze cell polarization, current density and temperature in solid oxide fuel cells (SOFCs). The increase of active sites is beneficial to improve efficiency of electrochemical reactions, but it can be also detrimental to SOFCs' stability as it will induce changes in strength and distribution of the thermal stresses. The variation of thermal stresses is systematically studied by grading the active site along the main flow direction. The results indicate that the first principle stress increases with the active site at the interface of electrolyte and electrode, but the shear stress mainly appears in the vicinity of gas inlets, which both suffer from a dramatic change when the active site is enhanced from the initial state to 1.5 times. Moreover, the electrolyte is subjected to large contrary tensile stresses, and the first principle stress is responsible for crack possibly occurring to the electrolyte. We also confirm that the sharp fluctuation of stress caused by the active sites can be relieved through adjusting thickness of the anode active layer.

Quaternary ammonium cations provide anionic conductivity in polymer ionomers and membranes. While study has been devoted to their alkaline stability and to improving hydroxide conductivity, there are limited studies on the electrode/cationic polymer interface. We use density functional theory (DFT) and cyclic voltammetry to examine the adsorption of tetramethyl-, tetraethyl-, tetrapropyl-, and benzyltrimethylammonium cations to platinum electrode surfaces. DFT results demonstrate that adsorption to Pt(111), Pt(100), and Pt(110) is favorable at low potentials in an alkaline electrolyte and that van der Waals interactions contribute significantly. Near-surface solvation weakens the adsorption of the long alkyl chain cations, and promotes the adsorption of the shorter chain cations, suggesting adsorption of shorter-chain cations may be possible at low potentials even in acidic electrolytes. The cations retain most of their charge on adsorption, which contributes to repulsive interactions between adsorbates. Steric hindrance further contributes to coverage dependence, with only low coverage adsorption (∼1/9–1/4 monolayer) being stable within the electrochemical window of an aqueous electrolyte. Our experimental results show that the quaternary ammonium cations blocked surface sites, hindering the adsorption of hydrogen and hydroxide. This observation is qualitatively consistent with DFT results, showing that these organic cations favorably adsorb at low potentials in alkaline electrolytes.

Corrosion behavior and cytotoxicity was reported for mixed brushite (BS)/hydroxyapatite (HA) coatings deposited on 316LSS substrate through a displacement reaction. Corrosion tests, carried out in a simulated body fluid, showed that in comparison with bare 316L, coating shifts E_corr to anodic values and reduces i_corr even if oscillations were observed, which were explained in terms of the chemical interactions at the solid/liquid interface. Cell biocompatibility of the coating was investigated through osteoblastic cell line MC3T3-E1, evidencing the absence of any cytotoxicity Taken together, the results show that galvanic deposition is a simple and cost-effective method for producing bioactive coatings which enhance corrosion resistance and biocompatibility of the substrate.

Review of the literature on the currently recognized, thirteen vitamins yields an overview of the electrochemical properties that include estimates of the formal potentials at physiological pH and identification of the general classes of redox mechanisms. All vitamins are electroactive and map a range of formal potentials over a 3 V window. The vitamins are grouped as lipid soluble (vitamins A, D, E, and K) and water soluble (B vitamins and vitamin C). Mechanisms are grouped as single electron transfer agents (B3, B7, B2, C, and D), vitamins that can be both oxidized and reduced (B1, B5, B6, B9, and E), and vitamins that undergo two successive, distinct reductions (B12 and K). Vitamin A voltammetry is uniquely complex. Plot of the formal potentials on a potential axis allows assessment of mechanistic paths to vitamin recycling, antioxidant behavior, pH dependence, electrochemical stability in air, acid, and water, electrochemical instability of vitamin pairs, and cooperative interactions between vitamins in medicine. The potential axis is shown as an effective tool for mapping thermodynamically complex interactions. The voltammetry literature for each vitamin is critically assessed.

Phenylethanolamine A (PEA) is used illegally and deposited in animal tissues. Due to the reason, it causes acute poisoning and symptoms of muscular tremors, nervousness. In present article, Ru@Au core-shell nanoparticles (Ru@Au NPs) involved in carbon nitride nanotubes (C₃N₄ NTs) functionalized graphene quantum dots (GQDs) nanocomposite based molecular imprinted polymer (MIP) was formed for PEA recognition. Firstly, C₃N₄ NTs@GQDs nanocomposite was prepared by means of hydrothermal treatment. Secondly, this nanocomposite was functionalized with 2-aminoethanethiol (AET) via the affinity of gold-sulfur for binding Ru@Au NPs. After that, PEA imprinted voltammetric sensor was prepared in presence of 100.0 mM phenol as monomer containing 25.0 mM PEA by cyclic voltammetry (CV). All nanomaterials' formation and properties were highlighted with scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray analysis (EDX), raman spectroscopy, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). 1.0 × 10⁻¹² - 1.0 × 10⁻⁹ M and 2.0 × 10⁻¹³ M were founded as the linearity range and the detection limit (LOD). Finally, PEA imprinted glassy carbon electrode (GCE) was used for urine sample analysis in presence of the other competitor agents such as clenbuterol (CLE), ractopamine (RAC) and salbutamol (SAL). In addition, the stability and repeatability of prepared sensor was investigated.

A new type of an electrochemical flow cell designed for exchangeable ultramicroelectrodes (UMEs) is presented. The cell could be used with up to 8 different UMEs allowing one to use this cell for UME array measurements. The cell was characterized using both empirical data and finite element modeling. Au and Pt UMEs were used to detect catechol simultaneously, demonstrating the ability of this cell to be used as a sensory platform. The electroanalytical response of flow system was validated by direct measurements of H₂O₂ concentrations. Finally, stochastic nanoparticle measurements were successfully performed using the flow system, highlighting the future possibilities of this system for environmental monitoring.

GO/TiO₂ nanotube array electrode was prepared on a titania plate by a simple in-situ anodization method. The physicochemical characteristics of synthesized TiO₂ and GO/TiO₂ electrodes were determined by Field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Raman Spectroscopy, Ultraviolet-vis diffuse reflectance spectroscopy (UV-vis DRS), Fourier Transform Infrared spectra (FTIR), Photoluminescence (PL) spectroscopy and X-ray photoelectron spectroscopy (XPS). Synthesized GO/TiO₂ nanotube electrodes were adjudged for its efficacy in the photoelectrocatalytic (PEC) degradation of Pentachlorophenol (PCP) aqueous solution. Box-Behnken design (BBD) was used to optimize the effect of graphene oxide (GO) loading (0.005–0.25 g/L), pH (3–8), applied current (20–60 mA) and degradation time (10–120 min) on the decomposition of PCP and energy consumption. At optimum conditions, 91% degradation and 85% mineralization of PCP was achieved after 90 min under UV-A illumination with 0.015 g/L of GO concentration, 20.68 mA applied current and at pH 3.14 by consuming 0.00068 kWh energy. Effect of reactive species scavengers on the degradation of PCP has been studied and hydroxyl radical was determined. Based on the LC-MS analysis results possible intermediates were identified and corresponding decomposition pathway of PCP was proposed.

This perspective article formalizes our proposal that the apparent hydrogen binding energy (HBE_app), which takes into account of the water adsorption energy as well as the intrinsic hydrogen binding energy (HBE) on metal surfaces, is the descriptor for hydrogen oxidation/evolution reactions (HOR/HERs). We show that the HBE_app, not HBE, is pH dependent and can be determined from the underpotential-deposited hydrogen peaks in cyclic voltammograms for platinum group metals including Pt, Ir, Pd, and Rh, and the decrease of their HOR/HER activities with pH is the result of a strengthened HBE_app due to a weakened water adsorption. Also discussed are the needs of further experimental and theoretical work to prove this hypothesis.

In this study, uniform and dense iron oxide α-Fe₂O₃ thin films were used as an electron-transport layer (ETL) in CH₃NH₃PbI₃-based perovskite solar cells (PSCs), replacing the Titanium dioxide (TiO₂) ETL conventionally used in planar heterojunction perovskite solar cells. The α-Fe₂O₃ films were synthesized using an electrodeposition method for the blocking layer and a hydrothermal method for the overlaying layer, while 2,2',7,7'-tetrakis (N, N'-di-p-methoxyphenylamine)-9,9' spirobifluorene (spiro-OMeTAD) was employed as a hole conductor in the solar cells. Based on the above synthesized α-Fe₂O₃ films the photovoltaic performance of the PSCs was studied. The α-Fe₂O₃ layers were found to have a significant impact on the photovoltaic conversion efficiency (PCE) of the PSCs. This was attributed to an efficient charge separation and transport due to a better coverage of the perovskite on the α-Fe₂O₃ films. As a result, the PCE measured under standard solar conditions (AM 1.5G, 100 mW cm⁻²) reached 5.7%.

Cation transport through a cellulose acetate-poly(N,N-dimethylaminoethyl methacrylate) membrane (CA:PDMAEMA) was studied with scanning electrochemical microscope (SECM) and the thickness increase of the membrane was monitored with ellipsometry. Upon addition of the polyelectrolyte PDMAEMA, the permeability of the probe cation (ferrocenium methanol, FcMeOH) was increased as much as 40-fold. Soaking membranes in an electrolyte solution doubled the permeability in plain CA membranes, whereas for PDMAEMA containing membranes the opposite was observed and the permeability was reduced by 20–40%. This time-dependent behavior is shown to be a result of the presence of PDMAEMA within the membrane matrix, thus providing an interesting platform for controllable membrane permeability.

In this work, a new biosensor using electrochemical magnetic loading of Tyrosinase (Tyr) immobilized on chitosan microspheres via in situ hybridization with Fe₃O₄ (Chitosan@Fe₃O₄) was developed. Fe₃O₄ was used to reduce the applied potential while chitosan microspheres helped in keeping the affinity with enzyme. The magnetic microspheres were characterized by scanning electron microscopy, Energy dispersive spectroscopy and Fourier transform Infra-red spectroscopy. These microspheres were confirmed to possess high electron transport performance of −50 mV. Parameters affecting the biosensor response such as amount of modifying material, pH, applied potential and temperature were optimized. The biosensor selectively detected catechol in a linear range from 2.64 × 10⁻⁶ M to 8.4 × 10⁻⁵ M at a sensitivity of 14.72 μA/mM with a limit of detection of 0.79 μM and a Michaelis–Menten constant (K_m^app) of 14.3 μM. The proposed design possesses attributes like cost effectiveness, ease of recycling and high selectivity in bio-sensing and thus can be deemed as a promising approach for commercial level biosensor synthesis.