Journal of The Electrochemical Society

Lithium iron phosphate (LFP) battery cells are ubiquitous in electric vehicles and stationary energy storage because they are cheap and have a long lifetime. This work compares LFP/graphite pouch cells undergoing charge-discharge cycles over five state of charge (SOC) windows (0%–25%, 0%–60%, 0%–80%, 0%–100%, and 75%–100%). Cycling LFP cells across a lower average SOC results in less capacity fade than cycling across a higher average SOC, regardless of depth of discharge. The primary capacity fade mechanism is lithium inventory loss due to: lithiated graphite reactivity with electrolyte, which increases incrementally with SOC, and lithium alkoxide species causing iron dissolution and deposition on the negative electrode at high SOC which further accelerates lithium inventory loss. Our results show that even low voltage LFP systems (3.65 V) have a tradeoff between average SOC and lifetime. Operating LFP cells at lower average SOC can extend their lifetime substantially in both EV and grid storage applications.

Water contaminants are a common cause of failure for polymer electrolyte membrane (PEM) electrolyzers in the field as well as a confounding factor in research on cell performance and durability. In this study, we investigated the performance impacts of feed water containing representative tap water cations at concentrations ranging from 0.5–500 μM, with conductivities spanning from ASTM Type II to tap-water levels. We present multiple diagnostic signatures to help identify the presence of contaminants in PEM electrolysis cells. Through analysis of polarization curves and impedance spectroscopy to understand the origins of performance losses, we found that a switch from the acidic to alkaline hydrogen evolution mechanism is a key factor in contaminated cell behavior. Finally, we demonstrated that this mechanism switching can be harnessed to remove cation contaminants and recover cell performance without the use of an acid wash. We demonstrated near-complete recovery of cells contaminated with sodium and calcium, and partial recovery of a cell contaminated with iron, which was further investigated by post-mortem microscopy. The improved understanding of contaminant impacts from this work can inform development of strategies to mitigate or recover performance losses as well as improve the consistency and rigor of electrolysis research.

We present a detailed examination of Ni corrosion in lithium-ion battery Ni-coated steel cylindrical cell hardware, focusing on LiPF₆-based electrolytes contaminated with water. The corrosion potential of the cell hardware is predominantly controlled by the iron component of the cylindrical can which cathodically protects the Ni coating. Despite the presence of cathodic protection, the Ni coating still experiences significant crevice corrosion, as confirmed through chemical aging tests. Mechanistic investigations on pure Ni metal reveal two distinct corrosion pathways depending on the presence or absence of oxygen in the electrolyte. The pathway involving oxygen proves to be more detrimental, as it oxidizes Ni in conjunction with acid, leading to the generation of water and the regeneration of corrosive species. This pathway exhibits corrosion rates two orders of magnitude higher than the alternative pathway. The dissolved Ni species predominantly exist in the +2 oxidation state and forms highly soluble F-rich compounds, comprising a mixture of associated species denoted by the formula Ni(P_xO_yF_z)_w. Finally, several suggestions for effectively mitigating Ni corrosion have been proposed, with alloying with chromium being the most effective.

Stress tests are developed that focus on anode catalyst layer degradation in proton exchange membrane electrolysis due to simulated start-stop operation. Ex situ testing indicates that repeated redox cycling accelerates catalyst dissolution, due to near-surface reduction and the higher dissolution kinetics of metals when cycling to high potentials. Similar results occur in situ, where a large decrease in cell kinetics (>70%) is found along with iridium migrating from the anode catalyst layer into the membrane. Additional processes are observed, however, including changes in iridium oxidation, the formation of thinner and denser catalyst layers, and platinum migration from the transport layer. Increased interfacial weakening is also found, adding to both ohmic and kinetic loss by adding contact resistances and isolating portions of the catalyst layer. Repeated shutoffs of the water flow further accelerate performance loss and increase the frequency of tearing and delamination at interfaces and within catalyst layers. These tests were applied to several commercial catalysts, where higher loss rates were observed for catalysts that contained ruthenium or high metal content. These results demonstrate the need to understand how operational stops occur, to identify how loss mechanisms are accelerated, and to develop strategies to limit performance loss.

In this study, the calendar aging of lithium-ion batteries is investigated at different temperatures for 16 states of charge (SoCs) from 0 to 100%. Three types of 18650 lithium-ion cells, containing different cathode materials, have been examined. Our study demonstrates that calendar aging does not increase steadily with the SoC. Instead, plateau regions, covering SoC intervals of more than 20%–30% of the cell capacity, are observed wherein the capacity fade is similar. Differential voltage analyses confirm that the capacity fade is mainly caused by a shift in the electrode balancing. Furthermore, our study reveals the high impact of the graphite electrode on calendar aging. Lower anode potentials, which aggravate electrolyte reduction and thus promote solid electrolyte interphase growth, have been identified as the main driver of capacity fade during storage. In the high SoC regime where the graphite anode is lithiated more than 50%, the low anode potential accelerates the loss of cyclable lithium, which in turn distorts the electrode balancing. Aging mechanisms induced by high cell potential, such as electrolyte oxidation or transition-metal dissolution, seem to play only a minor role. To maximize battery life, high storage SoCs corresponding to low anode potential should be avoided.

Energy storage systems with Li-ion batteries are increasingly deployed to maintain a robust and resilient grid and facilitate the integration of renewable energy resources. However, appropriate selection of cells for different applications is difficult due to limited public data comparing the most commonly used off-the-shelf Li-ion chemistries under the same operating conditions. This article details a multi-year cycling study of commercial LiFePO₄ (LFP), LiNi_xCo_yAl_1−x−yO₂ (NCA), and LiNi_xMn_yCo_1−x−yO₂ (NMC) cells, varying the discharge rate, depth of discharge (DOD), and environment temperature. The capacity and discharge energy retention, as well as the round-trip efficiency, were compared. Even when operated within manufacturer specifications, the range of cycling conditions had a profound effect on cell degradation, with time to reach 80% capacity varying by thousands of hours and cycle counts among cells of each chemistry. The degradation of cells in this study was compared to that of similar cells in previous studies to identify universal trends and to provide a standard deviation for performance. All cycling files have been made publicly available at batteryarchive.org, a recently developed repository for visualization and comparison of battery data, to facilitate future experimental and modeling efforts.

Battery research depends upon up-to-date information on the cell characteristics found in current electric vehicles, which is exacerbated by the deployment of novel formats and architectures. This necessitates open access to cell characterization data. Therefore, this study examines the architecture and performance of first-generation Tesla 4680 cells in detail, both by electrical characterization and thermal investigations at cell-level and by disassembling one cell down to the material level including a three-electrode analysis. The cell teardown reveals the complex cell architecture with electrode disks of hexagonal symmetry as well as an electrode winding consisting of a double-sided and homogeneously coated cathode and anode, two separators and no mandrel. A solvent-free anode fabrication and coating process can be derived. Energy-dispersive X-ray spectroscopy as well as differential voltage, incremental capacity and three-electrode analysis confirm a NMC811 cathode and a pure graphite anode without silicon. On cell-level, energy densities of 622.4 Wh/L and 232.5 Wh/kg were determined while characteristic state-of-charge dependencies regarding resistance and impedance behavior are revealed using hybrid pulse power characterization and electrochemical impedance spectroscopy. A comparatively high surface temperature of ∼70 °C is observed when charging at 2C without active cooling. All measurement data of this characterization study are provided as open source.

This year, the battery industry celebrates the 25^th anniversary of the introduction of the lithium ion rechargeable battery by Sony Corporation. The discovery of the system dates back to earlier work by Asahi Kasei in Japan, which used a combination of lower temperature carbons for the negative electrode to prevent solvent degradation and lithium cobalt dioxide modified somewhat from Goodenough's earlier work. The development by Sony was carried out within a few years by bringing together technology in film coating from their magnetic tape division and electrochemical technology from their battery division. The past 25 years has shown rapid growth in the sales and in the benefits of lithium ion in comparison to all the earlier rechargeable battery systems. Recent work on new materials shows that there is a good likelihood that the lithium ion battery will continue to improve in cost, energy, safety and power capability and will be a formidable competitor for some years to come.

Due to its high specific capacity, silicon is one of the most promising anode materials for next-generation lithium-ion batteries. However, its large volumetric changes upon (de)lithiation of ∼300% lead to a rupture/re-formation of the solid-electrolyte interphase (SEI) upon cycling, resulting in continuous electrolyte consumption and irreversible loss of lithium. Therefore, it is crucial to use electrolyte systems that form a more stable SEI that can withstand large volume changes. Here, we investigate lithium nitrate (LiNO₃) and lithium nitrite (LiNO₂) as electrolyte additives. Linear scan voltammetry on carbon black working electrodes in a half-cell configuration with LiNO₃-containing 1 M LiPF₆ in EC/DEC (1/2 v/v) revealed a two-step reduction mechanism, whereby the first reduction peak could be attributed to the conversion of LiNO₃ to LiNO₂, while X-ray photoelectron spectroscopy on harvested electrodes suggests the formation of Li₃N during the second reduction peak. On-line electrochemical mass spectrometry (OEMS) on carbon black electrodes showed that N₂O gas is evolved upon the reduction of LiNO₃- and LiNO₂-containing electrolytes but that the gassing associated with EC reduction is significantly reduced. Furthermore, OEMS and voltammetry were used to examine the redox chemistry of LiNO₂ additive. Finally, LiNO₃ and LiNO₂ additives significantly improved the cycle-life of Si||NCM622 full-cells.

Degradation models are important tools for understanding and mitigating lithium-ion battery aging, yet a universal model that can predict degradation under all operating conditions remains elusive. One challenge is the coupled influence of calendar and cycle aging phases on degradation mechanisms, such as solid electrolyte interphase (SEI) formation. In this work, we identify and systematically compare three different SEI interaction theories found in the literature, and apply them to experimental degradation data from a commercial lithium-ion cell. In a step-by-step process, and after careful data selection, we show that SEI delamination without any cracking of the active particles, and SEI microcracking, where cycling only affects SEI growth during the cycle itself, are both unlikely candidates. Instead, the results indicate that upon cycling, both the SEI and the active particle crack, and we provide a simple, 4-parameter equation that can predict the particle crack rate. Contrary to the widely-accepted Paris' law, the particle crack rate decreases with increasing cycles, potentially due to changing intercalation dynamics resulting from the increasing surface-to-volume ratio of the active particles. The proposed model predicts SEI formation accurately at different storage conditions, while simply adding the degradation from pure calendar and cycle aging underestimates the total degradation.

Redox mediators (RMs) suppress the charging overpotential to enhance the cycle performance of lithium-air batteries (LABs), but inappropriate RM incorporation can adversely shorten cycle life. In this study, three typical organic RMs; tetrathiafulvalene (TTF), 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO), and 10-methylphenothiazine (MPT), were incorporated into the air-electrode (AE) of the LAB (RM-on-AE), rather than dissolving them in the electrolyte (RM-in-EL), to maximize the RM effect throughout the cycle life. The discharge/charge cycle test confirmed that the cells with RM-on-AE prevented the reductive decomposition of RM with the lithium anode, deriving the RM effect for a longer cycle life than the cells with RM-in-EL. The measurement of AE deposits revealed that the TTF- and TEMPO-on-AE cells failed to generate a quantitative amount of Li₂O₂ discharge product. In contrast, the MPT-on-AE provided a 96% yield of Li₂O₂ after the first discharge because of the reductive tolerance of the MPT as organic RM. The quantitative analysis also revealed an accumulation of Li₂CO₃ on the AEs, along with the generation of carboxylate, as the side products of irrelevant battery reactions. This study provides a practical methodology for selecting RMs and their incorporation for developing long-life LABs.

Layered Mn-based transition metal oxides have gained interest as positive electrode materials for K-ion batteries due to their high capacity, excellent structural stability, and abundant resources. However, their practical utility is significantly hindered by insufficient electrochemical performances during operations. This study reports the successful synthesis of P3-K_0.46MnO₂ via the solid-state method and investigates its charge–discharge behavior as a positive electrode working in an FSA-based (FSA= bis(fluorosulfonyl)amide) ionic liquid electrolyte at 298 K. The K_0.46MnO₂ electrode demonstrates superior performance compared to previously reported K_xMnO₂ counterparts, delivering a reversible discharge capacity of about 100 mAh g⁻¹ at a current density of 20 mA g⁻¹ and a capacity retention of 68.3% over 400 cycles at 100 mA g⁻¹. Ex situ X-ray diffraction analyses confirm the occurrence of reversible structural changes during the charge–discharge process. Further, we explore potassium storage mechanisms through ex situ synchrotron soft X-ray absorption spectroscopy. Spectra obtained in Mn L-edge region suggest that Mn is reversibly oxidized and reduced during K⁺ deintercalation and intercalation processes. Remarkably, discharging the electrode below 2.3 V induces reversible formation of Mn²⁺ from Mn^3+/4+ on the electrode surface. The study demonstrates superior electrochemical performance of K_0.46MnO₂ positive electrode for K-ion battery using ionic liquid electrolyte.

The solvent-free dry processing of electrodes is highly desirable to reduce the manufacturing cost of lithium-ion batteries (LIBs) and increase the active mass loading in the electrode. The drying process is based on the fibrillation of the polytetrafluoroethylene binder induced by shear force. This technique offers the advantage of uniformly dispersing the active material and conductive carbon without binder migration, thereby facilitating the fabrication of thick electrode with high mass loading. In this study, we explored the influence of conductive carbon morphology on the cycling performance of dry-processed LiNi_0.82Co_0.10Mn_0.08O₂ (NCM) cathodes. In contrast to Super P, which provided electronic pathways through point-contact, the fibrous structure of the vapor-grown carbon fibers (VGCFs) promoted line-contact, ensuring long and less-torturous electronic pathways and enhanced utilization of active materials. Consequently, the cathode employing fibrous VGCFs achieved higher electrical conductivity, resulting in enhanced electrochemical performance. The dry-processed NCM cathode employing VGCF with an areal capacity of 8.5 mAh cm⁻² delivered a high discharge capacity of 212 mAh g⁻¹ with good capacity retention. X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were conducted to investigate the degradation behavior of the high-mass-loaded cathodes with two different conductive carbons.

In this work, the electrodeposition reaction of Am in AmCl₃-LiCl-KCl molten salt was studied using voltammetry and chronoamperometry. Electrodeposition of Am was shown to proceed via a two $-$ step reaction scheme, involving the one-electron transfer reduction of Am³⁺ to Am²⁺, followed by the two-electron transfer reduction of intermediate Am²⁺ to Am⁰. A low Coulombic efficiency of Am deposition was measured despite the Am deposition occurring within the thermodynamic stability window of the supporting LiCl-KCl electrolyte. We hypothesize that the low efficiency is due to out-diffusion of the intermediate Am²⁺ species away from the electrode surface. Experimental observations provide evidence of a kinetically $-$ limited electrodeposition reaction, which allows for the loss of intermediate Am²⁺ via diffusion leading to Am deposition inefficiency.

Highlights

• The electrochemical behavior of americium, a minor actinide produced only by nuclear fission, was studied to provide fundamental insight for recovery from used nuclear fuel.

• This work investigated the irreversibility and low-coulombic efficiency of the Am deposition reaction in molten salt via transient measurements.

• Coulombic inefficiencies during Am deposition were observed during steady-state coulometric measurements.

High-concentration Li salt/sulfone solutions have attracted attention as promising liquid electrolytes for Li batteries owing to their high oxidative stability, nonflammability, and high Li⁺ ion transference number (t_Li+). Herein, we report the temperature-dependent electrolyte properties of a sulfone-based ternary mixture composed of LiN(SO₂F)₂, sulfolane, and dimethyl sulfone, which enables Li batteries to operate in a wide temperature range. At −20 °C, the rate capability of a Li/LiCoO₂ cell with the sulfone-based electrolyte was comparable to that with a conventional carbonate-based electrolyte, even though the ionic conductivity of the electrolyte was significantly lower in the former case (0.11 versus 2.92 mS cm⁻¹). This is because the former electrolyte has a higher t_Li+ value, effectively suppressing the concentration overpotential during cell charging and discharging. Moreover, the vapor pressure was much lower for the sulfone-based electrolyte than for the carbonate-based one, and the Li/LiCoO₂ cell with the former electrolyte was successfully operated at 60 °C. This study provides insights into the characteristics of high-concentration electrolytes that affect the temperature dependence of Li battery performance.

There is a rising demand for energy storage systems (ESS) that are both environmentally sustainable and high-performing. To meet the prerequisites of diverse energy-consuming applications, developing novel, better-quality and highly-performing electrode materials for ESS is vital. In this quest, graphene emerges as a wonder material, ascribed to its unmatched mechanical, electrical and thermal behaviour. Different ESS can be significantly developed with enhanced energy storage capacity with the application of graphene. Herein, a brief discussion of the structure and synthesis techniques for graphene and its derivatives is presented. In addition to this, the study also offers a comprehensive summary on the latest developments in lithium-ion batteries, double-layer supercapacitors, pseudo capacitors and hybrid supercapacitors using graphene as the dominant material for anode/cathode electrodes in the form of composites and hybrids. The effect of the graphene on the performance metrics of the EESS has also been imparted. Despite the promising advancements, the key challenges and limitations in the development of graphene-based high-performing energy storage devices are described in detail. The article concludes with the potential prospects of energy storage using graphene are also discussed.

Biosensors are inevitable tools for biomedical applications, including disease diagnosis, monitoring, and drug management. Integrated with nanotechnology, these biosensors have improved patient outcomes by providing rapid diagnosis, strategic prognosis, and remote access, decreasing the burden of present-day healthcare facilities. Due to enhanced surface-to-volume ratio and tunable physicochemical properties of nanomaterials, nanotechnology-based biosensors have emerged as transformative tools in the biomedical sector, offering unparalleled sensitivity and specificity for detecting and analyzing biological molecules for targeted disease diagnosis. This review explores the advancements in biosensor technology, emphasizing the integration of various nanomaterials, including metal nanoparticles, carbon nanomaterials, and quantum dots, to enhance device performance in terms of sensitivity, selectivity, and stability. We discuss the operational principles of different biosensor types- such as electrochemical, optical, solid-state, and DNA-based sensors and their applications in healthcare, from early disease detection to personalized treatment management. Moreover, the review delves into the challenges, alternate solutions, and future prospects of biosensor development, highlighting the role of artificial intelligence, bioinformatics, and 5 G communication in creating next-generation smart biosensors for healthcare applications.

During steady-state operation, the proton conduction profile and the concentration profiles of the reactants and products transported through catalyst layers are non-uniform in the in-plane and through-plane directions. It is, therefore, a reasonable hypothesis that the optimal arrangement of the constituents of the catalyst layers should also be non-uniform. One way to address the non-uniformity is through graded catalyst layers. This study elucidates the state-of-the-art for graded catalyst layers, which so far were primarily investigated for proton exchange membrane fuel cells (PEMFCs). We identify the most impactful types of gradients in the PEMFC cathode and highlight studies displaying their merits in terms of better conversion efficiencies and longer lifetimes. Furthermore, two critical issues that have received little attention so far are emphasized: on the one hand, industrially relevant manufacturing techniques must be developed and implemented. On the other hand, suitable techniques are needed to identify and characterize the gradients. In this study, guidance to navigate both of these challenges is offered.

Electrochemical machining (ECM) is an efficient and precise manufacturing technology with broad prospects for numerous applications. As a subset of electrochemical machining, electrochemical polishing (ECP) is an advanced surface finishing method that utilizes electrochemical principles to produce smooth and reflective surfaces on various materials, particularly metals. This process is distinguished by its ability to refine surfaces without causing scratches or other forms of mechanical damage, thereby providing a significant advantage over traditional mechanical polishing techniques. The high processing efficiency of ECP renders it particularly suitable for industries that demand large-scale production and high-quality surface finishes. This work reviews the fundamental aspects of ECP, comparing three mechanisms: viscous film theory, salt film theory, and enhanced oxidation–dissolution equilibrium theory. Furthermore, it examines the factors influencing the effectiveness of ECP, including electrolyte composition, temperature, electropolishing time, voltage, and current. Applications of ECP in stainless steel, copper, nickel, and tungsten are also explored, along with a summary of its integration with advanced technologies. Finally, perspectives on the future development of ECP are discussed.

The burgeoning intersection of machine learning (ML) with electrochemical sensing heralds a transformative era in analytical science, pushing the boundaries of what's possible in detecting and quantifying chemical substances with unprecedented precision and efficiency. This convergence has accelerated a number of discoveries, improving electrochemical sensors' sensitivity, selectivity, and ability to comprehend complicated data streams in real-time. Such advancements are crucial across various applications, from monitoring health biomarkers to detecting environmental pollutants and ensuring industrial safety. Yet, this integration is not without its challenges; it necessitates navigating intricate ethical considerations around data use, ensuring robust data privacy measures, and developing specialized software tools that balance accessibility and security. As the field progresses, addressing these challenges head-on is essential for harnessing the full potential of ML-enhanced electrochemical sensing. This review briefly explores these dimensions, spotlighting the significant technological strides, the ethical landscape, and the dynamic interplay between open-source and proprietary software solutions while also casting a forward gaze at the promising future directions of this interdisciplinary venture.

The kinetics of composite cathodes for solid-state batteries (SSBs) relies heavily on their microstructure. Spatial distribution of the different phases, porosity, interface areas, and tortuosity factors are important descriptors that need accurate quantification for models to predict the electrochemistry and mechanics of SSBs. In this study, high-resolution focused ion beam-scanning electron microscopy tomography was used to investigate the microstructure of cathodes composed of a nickel-rich cathode active material (NCM) and a thiophosphate-based inorganic solid electrolyte (ISE). The influence of the ISE particle size on the microstructure of the cathode was visualized by 3D reconstruction and charge transport simulation. By comparison of experimentally determined and simulated conductivities of composite cathodes with different ISE particle sizes, the electrode charge transport kinetics is evaluated. Porosity is shown to have a major influence on the cell kinetics and the evaluation of the active mass of electrochemically active particles reveals a higher fraction of connected NCM particles in electrode composites utilizing smaller ISE particles. The results highlight the importance of homogeneous and optimized microstructures for high performance SSBs, securing fast ion and electron transport.

Li-In electrodes are widely applied as counter electrodes in fundamental research on Li-metal all-solid-state batteries. It is commonly assumed that the Li-In anode is not rate limiting, i.e. the measurement results are expected to be representative of the investigated electrode of interest. However, this assumption is rarely verified, and some counterexamples were recently demonstrated in literature. Herein, we fabricate Li-In anodes in three different ways and systematically evaluate the electrochemical properties in two- and three-electrode half-cells. The most common method of pressing Li and In metal sheets together during cell assembly resulted in poor homogeneity and low rate performance, which may result in data misinterpretation when applied for investigations on cathodic phenomena. The formation of a Li-poor region on the separator side of the anode is identified as a major kinetic bottleneck. An alternative fabrication of a Li-In powder anode resulted in no kinetic benefits. In contrast, preparing a composite from Li-In powder and sulfide electrolyte powder alleviated the kinetic limitation, resulted in superior rate performance, and minimized the impedance. The results emphasize the need to fabricate optimized Li-In anodes to ensure suitability as a counter electrode in solid-state cells.

Highlights

• The fabrication of Li-In anodes needs to be optimized to ensure suitability as a counter electrode in sulfide all-solid-state batteries.

• The Li-In counter electrode may often be the limiting factor of sulfide all-solid-state halfcells.

• Pressing Li and In foil together results in a kinetically limited anode.

• Composites from Li-In and sulfide electrolyte result in stable reference potential, superior rate performance and low impedance of the counter electrode.

Electrical discharge micromachining (EDM) poses challenges to the fatigue-life performance of machined surfaces due to thermal damage, including recast layers, heat-affected zones, residual stress, micro-cracks, and pores. Existing literature proposes various ex situ post-processing techniques to mitigate these effects, albeit requiring separate facilities, leading to increased time and costs. This research involves an in situ sequential electrochemical post-processing (ECPP) technique to enhance the quality of EDMed micro-holes on titanium. The study develops an understanding of the evolution of overcutting during ECPP, conducting unique experiments that involve adjusting the initial radial interelectrode gap (utilizing in situ wire-electrical discharge grinding) and applied voltage. Additionally, an experimentally validated transient finite element method (FEM) model is developed, incorporating the passive film formation phenomenon for improved accuracy. Compared to EDM alone, the sequential EDM-ECPP approach produced micro-holes with superior surface integrity and form accuracy, completely eliminating thermal damage. Notably, surface roughness (Sa) was reduced by 80% after the ECPP. Increasing the voltage from 8 to 16 V or decreasing the gap from 60 to 20 μm rendered a larger overcut. This research's novelty lies in using a two-phase dielectric (water-air), effectively addressing dielectric and electrolyte cross-contamination issues, rendering it suitable for commercial applications.

Highlights

• Better micro-hole quality through in situ sequential eco-friendly near-dry EDM & ECM

• Successfully resolved dielectric-electrolyte cross-contamination in sequential processes

• Unique experiments that adjust the initial radial IEG using in situ wire-EDG

• Developed and validated a transient FEM model, incorporating passivation aspect

• Achieved recast layer-free holes with Sa values approximately 80% lower than EDM holes

Vanadium dioxide is widely known for its metal-insulator transition (MIT), in which drastic changes in resistivity and IR-transparency occur. This makes VO₂ thin films promising materials for high-frequency optoelectronic devices. To get the most MIT sharpness, thin films should not contain impurities of hyper-oxygen or hypo-oxygen phases arising during VO₂ synthesis. To ascertain the conditions of single-phase VO₂ existence, the equilibrium boundaries of VO₂ with neighboring phases were determined using the electromotive force method (EMF) with a solid electrolyte ZrO₂(Y₂O₃). Our data for the high-oxygen boundary of VO₂ existence in equilibrium with the V₆O₁₃ phase agree with the only data known in the literature. We established that VO₂ is, in equilibrium with the V₉O₁₇ phase at the low-oxygen boundary, which forms V₈O₁₅ under further reduction. The temperature of the peritectoid decomposition of V₉O₁₇ is established, and the corresponding corrections to the phase diagram of the vanadium-oxygen system are introduced. The Gibbs energies for V₉O₁₇, V₈O₁₅, and V₆O₁₃ formation reactions are calculated. It is also shown that the IR reflectance of VO₂ films brought to equilibrium at the high-oxygen boundary is much greater than that of films equilibrated at the low-oxygen boundary.

Highlights

• Equilibrium boundaries of VO₂ phase stability were studied by the EMF method.

• Low-oxygen boundary revealed more complex equilibriums than previously assumed.

• Thermodynamic data about equilibriums of V₈O₁₅, V₉O₁₇, VO₂, V₆O₁₃ were obtained.

• New information was added to the phase diagram of the vanadium-oxygen system.

• Influence of nonstoicometry on MIT was shown by IR experiments with thin VO₂ films.

Electrochemical Impedance Spectroscopy (EIS) is a powerful tool for electrochemical analysis; however, its data can be challenging to interpret. Here, we introduce a new open-source tool named AutoEIS that assists EIS analysis by automatically proposing statistically plausible equivalent circuit models (ECMs). AutoEIS does this without requiring an exhaustive mechanistic understanding of the electrochemical systems. We demonstrate the generalizability of AutoEIS by using it to analyze EIS datasets from three distinct electrochemical systems, including thin-film oxygen evolution reaction (OER) electrocatalysis, corrosion of self-healing multi-principal components alloys, and a carbon dioxide reduction electrolyzer device. In each case, AutoEIS identified competitive or in some cases superior ECMs to those recommended by experts and provided statistical indicators of the preferred solution. The results demonstrated AutoEIS's capability to facilitate EIS analysis without expert labels while diminishing user bias in a high-throughput manner. AutoEIS provides a generalized automated approach to facilitate EIS analysis spanning a broad suite of electrochemical applications with minimal prior knowledge of the system required. This tool holds great potential in improving the efficiency, accuracy, and ease of EIS analysis and thus creates an avenue to the widespread use of EIS in accelerating the development of new electrochemical materials and devices.

Highlights

• A novel tool that automatically generates candidate ECMs for EIS analysis without training data

• Generalizable across various electrochemical systems

• Minimized human bias and expert knowledge requirements

• Reproducible ECM exploration with explicit, measurable, and traceable biases

• High-throughput EIS analysis to accelerate electrochemical materials research

In the modern world, population growth, industrialization, and lifestyle changes have led to a rise in existing and new diseases, increasing global drug consumption. Proper pharmaceutical dosage is vital since drugs are only effective within specific concentration ranges. Therefore, developing reliable analytical methods for drug analysis in pharmaceuticals and biological samples is essential. Electroanalytical methods are particularly advantageous due to their low cost, ease of use, and rapid response. This study introduces a highly sensitive electrochemical sensor based on thioglycolic acid (TA)-decorated metallic phase molybdenum disulfide (MP-MoS2) nanosheets for the selective detection of molnupiravir (MOL), an antiviral drug used in Covid-19 treatment. The TA@MP-MoS2 nanomaterial was characterized using FTIR, TEM, and EIS. Screen-printed carbon electrodes (SPCE) were modified with TA@MP-MoS2 nanosheets to evaluate their electro-chemical and catalytic behaviours towards MOL by cyclic voltammetry (CV) and square wave voltammetry (SWV). The sensor displayed a well-defined electro-oxidation signal for MOL at 0.534 V, with the linear responses in two concentration ranges: 0.50 – 3.40 µM and 3.40 – 9.55 µM, and a low detection limit of 22.6 nM. The proposed design that has promising results could be an alternative strategy to fabricate the sensitive sensor for the detection of antiviral agents in real samples

All-solid-state batteries (ASSBs) are promising next-generation batteries owing to their improved safety compared with lithium-ion batteries using flammable liquid electrolytes. Among various solid electrolytes, sulfide-based electrolytes exhibit high ionic conductivities, and their ductile properties allow them to be easily processed without high-temperature sintering. In sulfide-based ASSBs, a polymer binder is essential for achieving a good cycling performance by maintaining strong interfacial contacts in the composite electrodes during cycling. In this study, we prepared a composite Si-C anode and a LiNi0.82Co0.1Mn0.08O2 cathode using a nitrile-butadiene rubber binder for ASSB applications, and investigated the effect of the binder content on the mechanical properties and electrochemical performance. The binder content significantly influenced the physical and electrochemical characteristics of the composite electrodes, and the ASSB prepared with 1.5 wt.% binder showed the best cycling performance considering capacity retention and rate capability. Furthermore, we investigated how the excess binder adversely affected the cycling performance through time-of-flight secondary ion mass spectrometry analysis.

The development of highly sensitive and specific diagnostic tools for early-stage detection of dengue virus (DENV) is critical for effective outbreak management, particularly in resource-limited settings. In this study, we report a novel electrochemical immunosensor based on bimetallic gold silver (Au-Ag) nanoparticles integrated with reduced graphene oxide (rGO) for the detection of dengue virus envelope (E) protein. The Au-Ag bimetallic nanostructures exhibit superior electron transfer kinetics and enhanced electrocatalytic activity, while rGO serves as an excellent platform due to its large surface area and high conductivity. This synergistic combination improves antigen-antibody interactions and significantly boosts sensor performance. The immunosensor demonstrated a broad linear detection range of 100 ag/mL to 10 ng/mL, with a high correlation coefficient (R² = 0.98519). It achieved an ultra-low limit of detection (LOD) of 4.959 ag/mL for DENV E protein, outperforming existing detection methods. These findings highlight the potential of the Au-Ag- rGO-based immunosensor as a promising tool for point-of-care diagnosis, enabling rapid and cost-effective disease management and control.

This article describes the development of a simple and sensitive voltammetric sensor for the simultaneous determination of Uric acid (UA) and Tyramine (TYM), which act as metabolic syndrome (Mts) biomarkers. The electropolymer of the naturally occurring amino acid citrulline (Cit) has been employed as the electrode modifier in this sensor. Glassy carbon electrode modified with poly citrulline has been characterized with the aid of techniques such as scanning electron microscopy (SEM) and SEM-energy dispersive X-ray analysis, surface area calculations and electrochemical impedance spectroscopy. Studies were carried out to optimize parameters like the cycles of polymerisation, supporting electrolyte and its pH. The sensor which offers fast determination of the analytes using square wave voltammetry possesses a limit of detection 1.32×10-8 M and 4.20×10-8 M for UA and TYM, respectively. The applicability of the sensor in body fluids has been proved through spike recovery analysis in artificial blood serum and urine samples. Interference on the voltammetric signals created by some dominant coexisting species of the analytes was found to be tolerable.

A hydrophobic aryl diazonium salt has been synthesized from 3,5-bis(trifluoromethyl)aniline and utilized to covalently modify graphene nanoplatelets and carbon nanotubes. The modified nanomaterials were applied on a screen-printed electrode/ion sensing membrane interface resulting in reduced potential drift to 100 μV/h compared to control sensors. Characterization was achieved through X-ray photoelectron spectroscopy. The electrode’s response was optimized using response surface methodology and then utilized for determination of 9-Aminoacridine (9-AA) in pharmaceutical gel dosage form and spiked human plasma without prior extraction steps. 9-AA is a fluorescent dye with antimicrobial activity that eradicates a range of microorganisms that can cause oral sores or broken skin and it has been recently used as anticancer among other uses as fluorescent dye and pH indicator. Accurate determination of 9-AA could help in adjusting dosages for each application. The optimized sensor was validated per IUPAC guidelines and obtained a wide linearity range from 1.0 × 10–7 M to 1.0 × 10–2 M, correlation coefficient of 0.9997, improved Nernstian slope 59.72, long term stability, and lower limit of detection (9.0 × 10–8 M). Furthermore, Analytical Eco-scale and AGREE methods were utilized to evaluate the presented method's greenness.

Layered Mn-based transition metal oxides have gained interest as positive electrode materials for K-ion batteries due to their high capacity, excellent structural stability, and abundant resources. However, their practical utility is significantly hindered by insufficient electrochemical performances during operations. This study reports the successful synthesis of P3-K_0.46MnO₂ via the solid-state method and investigates its charge–discharge behavior as a positive electrode working in an FSA-based (FSA= bis(fluorosulfonyl)amide) ionic liquid electrolyte at 298 K. The K_0.46MnO₂ electrode demonstrates superior performance compared to previously reported K_xMnO₂ counterparts, delivering a reversible discharge capacity of about 100 mAh g⁻¹ at a current density of 20 mA g⁻¹ and a capacity retention of 68.3% over 400 cycles at 100 mA g⁻¹. Ex situ X-ray diffraction analyses confirm the occurrence of reversible structural changes during the charge–discharge process. Further, we explore potassium storage mechanisms through ex situ synchrotron soft X-ray absorption spectroscopy. Spectra obtained in Mn L-edge region suggest that Mn is reversibly oxidized and reduced during K⁺ deintercalation and intercalation processes. Remarkably, discharging the electrode below 2.3 V induces reversible formation of Mn²⁺ from Mn^3+/4+ on the electrode surface. The study demonstrates superior electrochemical performance of K_0.46MnO₂ positive electrode for K-ion battery using ionic liquid electrolyte.

In this work, the electrodeposition reaction of Am in AmCl₃-LiCl-KCl molten salt was studied using voltammetry and chronoamperometry. Electrodeposition of Am was shown to proceed via a two $-$ step reaction scheme, involving the one-electron transfer reduction of Am³⁺ to Am²⁺, followed by the two-electron transfer reduction of intermediate Am²⁺ to Am⁰. A low Coulombic efficiency of Am deposition was measured despite the Am deposition occurring within the thermodynamic stability window of the supporting LiCl-KCl electrolyte. We hypothesize that the low efficiency is due to out-diffusion of the intermediate Am²⁺ species away from the electrode surface. Experimental observations provide evidence of a kinetically $-$ limited electrodeposition reaction, which allows for the loss of intermediate Am²⁺ via diffusion leading to Am deposition inefficiency.

Highlights

• The electrochemical behavior of americium, a minor actinide produced only by nuclear fission, was studied to provide fundamental insight for recovery from used nuclear fuel.

• This work investigated the irreversibility and low-coulombic efficiency of the Am deposition reaction in molten salt via transient measurements.

• Coulombic inefficiencies during Am deposition were observed during steady-state coulometric measurements.

High-concentration Li salt/sulfone solutions have attracted attention as promising liquid electrolytes for Li batteries owing to their high oxidative stability, nonflammability, and high Li⁺ ion transference number (t_Li+). Herein, we report the temperature-dependent electrolyte properties of a sulfone-based ternary mixture composed of LiN(SO₂F)₂, sulfolane, and dimethyl sulfone, which enables Li batteries to operate in a wide temperature range. At −20 °C, the rate capability of a Li/LiCoO₂ cell with the sulfone-based electrolyte was comparable to that with a conventional carbonate-based electrolyte, even though the ionic conductivity of the electrolyte was significantly lower in the former case (0.11 versus 2.92 mS cm⁻¹). This is because the former electrolyte has a higher t_Li+ value, effectively suppressing the concentration overpotential during cell charging and discharging. Moreover, the vapor pressure was much lower for the sulfone-based electrolyte than for the carbonate-based one, and the Li/LiCoO₂ cell with the former electrolyte was successfully operated at 60 °C. This study provides insights into the characteristics of high-concentration electrolytes that affect the temperature dependence of Li battery performance.

Microscale silicon particles have a higher specific capacity but larger volume expansion than graphite particles, leading to particle decoupling and lifetime limitations. This study investigates a wide range of external mechanical pressures from zero (ZP - 0.00 MPa) to high (HP - 0.50 MPa) pressure to determine the optimal pressure for high rate capability, cyclic lifetime, energy density, low temperature rise, and low cell thickness gain. The cells are characterized by rate tests and impedance spectroscopy, and are aged until 70% state of health (SoH). The post-mortem analysis after 70% SoH and thickness measurements over 360 cycles in a compression test bench offer insights into the thickness gain. Electrochemical results reveal an immediate reduction in discharge capacity upon transitioning from normal pressure (NP - 0.20 MPa) to ZP, with NP and HP exhibiting superior performance over aging. The impedance was reduced initially and over aging for higher mechanical pressures, especially the cathode contact resistance, resulting in lower temperature rises during the rate tests. Overall, applying higher pressures reduced the anode and cell thickness gain. Moreover, the porosity decreased with increasing pressure, as determined by mercury intrusion porosimetry and pycnometer measurements. The increase of the anode mass correlates to the total charge throughput, which is pressure-dependent and the highest for NP.

Meeting the increasing demand for lithium in vehicle electrification and renewable energy storage requires innovations in lithium-ion (Li⁺) separations. Traditional solar evaporation methods for lithium recovery are slow and consume tremendous volumes of water and secondary chemicals (acids and bases). This study introduces a bipolar membrane capacitive deionization (BPM-CDI) unit for direct lithium extraction and LiOH production without the external addition of acids and bases. Utilizing de-lithiated lithium-iron-phosphate (LFP) coated carbon cloth electrodes, the BPM-CDI unit demonstrates selective Li⁺ capture over competing ions. Molecular dynamics simulations and H-cell experiments elucidate pH inversion mechanisms during Li⁺ release, yielding LiOH. The BPM-CDI platform efficiently removes Li⁺ from synthetic brines featuring 8x higher Mg²⁺ concentrations (200 ppm Mg²⁺) and 26x higher Na⁺ concentrations (682 ppm Na⁺), achieving a LiOH concentration of 124 ppm (36 ppm Li⁺) after 8 cycles of recirculation. Post-mortem analysis confirms electrode integrity and stability. BPM-CDI integrated with selective electrodes is a promising electrochemical separation-reactor platform for lithium recovery while producing LiOH.

This study involved an investigation of the role of boric acid in nickel electroforming from sulfamate electrolytes, especially in relation to its ability to minimise interfacial pH changes during electrodeposition. Initial speciation calculations indicated that buffering by polyborate species and nickel-borate complexes are most likely responsible for this effect. However, the concentration of nickel-borate complexes was too low even at elevated pH to be a significant electroactive species. Polarisation and electrochemical quartz crystal microbalance measurements indicated that, in the absence of boric acid, electrodeposits typically contained Ni(OH)₂, while boric acid additions resulted in pure Ni being deposited with a current efficiency approaching unity. Boric acid additions substantially modified the nickel and hydrogen partial currents, and influenced the overall current efficiency. Studies in nickel-free solutions indicated that boric acid adsorbs on the surface which explains the suppression of H₂O reduction observed in the electroforming experiments. Collectively, solution buffering due to polyborate and nickel-borate species and inhibition of H₂O reduction by adsorbed boric acid minimised interfacial pH changes and prevented the formation of nickel hydroxide.

LiNixCoyMn1-x-yO2 (NCM) cathodes, especially with high Ni content, are widely expected to keep advancing the energy density of Li-ion batteries. However, ensuring a good cycle life remains a key challenge. Applying inert protective coatings on the surface of NCMs is a common route for mitigating surface-based degradation. In this study a sustainable ethanol-based wet-chemical coating method for covering the material with Al2O3 is developed and demonstrated on NCM111. The effect of the synthesis procedure is carefully evaluated to distinguish the benefits of the protective coating from the contributions of re-sintering and removal of surface contaminants, all taking place during the synthesis of the coated material. We show that while the cycling stability is significantly improved by the material regeneration alone (65 % vs. 79 % state-of-health after 500 charge-discharge cycles at voltage range 2.7 – 4.3 V vs. Li/Li+), the Al2O3-coated material displays further cycle life gains, maintaining 88% of initial capacity after 500 charge-discharge cycles. This work thus demonstrates both a sustainable wet-chemical coating method and the importance of establishing a proper baseline for characterization of inert protective coatings in general. The importance of both gains further prominence with the transition to inherently less stable higher Ni content NCMs.

In Part 1 of this paper, the temperature impact on the Multi-Species, Multi Reaction (MSMR) model was studied. This was accomplished by acquiring data from slow rate lithiation and delithiation of a meso-carbon micro-bead (MCMB) graphite. Through this analysis, the temperature impact on the total fraction of available host sites in a particular MSMR gallery (X_j), the impact on the reference potential (${{\rm{U}}}_{{\rm{j}}}^{{\rm{o}}}$), and the impact on the parameter detailing the deviation from Nernstian behavior (ω_j) was determined. Here, the intercalation material is discussed, compared to traditional methods of acquiring the entropy coefficient, and comparison is made to previous mathematical estimates. Some of the challenges in using temperature dependent constant rate charge and discharge data as compared to the potentiodynamic entropy coefficient calculation method are also discussed, and a recommendation for future applications is proposed.

Cyclic volume changes and non-uniform electrodeposition/stripping, among other cycling-induced chemo-mechanical degradation of lithium metal and lithium-alloy solid state batteries, lead to contact loss between the anode and the solid electrolyte separator. Operando experiments have shown accelerated short-circuiting behavior due to contact loss in "anode-free" solid-state batteries. Simulations have shown the relationship between active area fraction and the ratio of effective conductivities in regular-shape active area configurations. Through modeling experiments using imputed active contact area of lithium-metal negative electrode batteries, we quantify the effects of this contact loss. Specifically, we (1) quantify the interfacial resistance due to this contact loss, (2) show non-uniform local current density distribution such that evaluation of what area fraction has current exceeding critical current densities is possible, and (3) show non-uniform reaction distribution at the positive electrode. This work sheds light on the tradeoffs in the design of solid state batteries within the context of contact loss.

Gas diffusion electrodes (GDEs) play a crucial role in the development of electrochemical CO₂ reduction (eCO₂R) toward an economically viable process. While membrane electrode assemblies (MEAs) are currently the most efficient approach due to their low cell voltage, electrolyte supported GDEs still present a valuable tool for the characterization of catalysts under industrially relevant current densities, allowing for direct measurement of the electrode potential against reference electrodes. In this study, common experimental methods of iR correction and pressure control in eCO₂R literature studies on GDEs are analyzed and compared regarding their potential impact on the reported results. It is revealed that failure to account for dynamic changes in iR-drop can lead to significant inaccuracies in reported electrode potentials. Additionally, common methods for the application of differential pressure across GDEs are shown to impact the performance, leading to additional errors in experimental results. Based on these findings, an experimental protocol for the application of single high frequency response as a method for iR correction is developed, providing a tool for reproducible electrochemical characterization of GDEs in eCO₂R.