Journal of The Electrochemical Society

Unwanted self-discharge of LFP/AG and NMC811/AG cells can be caused by in situ generation of a redox shuttle molecule after formation at elevated temperature with common alkyl carbonate electrolyte. This study investigates the redox shuttle generation for several electrolyte additives, e.g., vinylene carbonate and lithium difluorophosphate, by measuring the additive reduction onset potential, first cycle inefficiency and gas evolution during formation at temperatures between 25 and 70 °C. After formation, electrolyte is extracted from pouch cells for visual inspection and quantification of redox shuttle activity in coin cells by cyclic voltammetry. The redox shuttle molecule is identified by GC-MS and NMR as dimethyl terephthalate. It is generated in the absence of an effective SEI-forming additive, according to a proposed formation mechanism that requires residual water in the electrolyte, catalytic quantities of lithium methoxide generated at the negative electrode and, surprisingly, polyethylene terephthalate tape within the cell.

Unwanted parasitic reactions in lithium-ion cells lead to self-discharge and inefficiency, especially at high temperatures. To understand the nature of those reactions this study investigates the open circuit storage losses of LFP/graphite and NMC811/graphite pouch cells with common alkyl carbonate electrolytes. The cells perform a storage test at 40 °C with a 500 h open circuit period after formation at temperatures between 40 °C and 70 °C. Cells formed at elevated temperature showed a high reversible storage loss that could be assigned to a redox shuttle generated in the electrolyte during formation. A voltage hold after formation can reduce the shuttle-induced self-discharge as indicated by significantly lower reversible storage losses, the absence of shuttling currents in cyclic voltammetry and improved metrics in ultra-high precision cycling. The addition of two weight percent vinylene carbonate can prevent redox shuttle generation and leads to almost zero reversible self-discharge.

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.

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.

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.

Lithium ion batteries (LIBs) have dominated the energy industry due to their unmatchable properties that include a high energy density, a compact design, and an ability to meet a number of required performance characteristics in comparison to other rechargeable systems. Both government agencies and industries are performing intensive research on Li-ion batteries for building an energy-sustainable economy. LIBs are single entities that consist of both organic and inorganic materials with features covering multiple length scales. Two vital parameters for LIBs are their stable and safe operation. Critical insights should be made for understanding the structure to property relationships and the behavior of components under the working condition of LIBs. Since, the cathode serves as a central component of LIBs, the overall cell performance is significantly affected by the chemical and physical properties of the cathode. Cathodes tend to react with the electrolytes and, hence, to undergo surface modifications accompanied by degradation. These side-reactions result in an erosion of battery performance, thereby causing a reduced battery life and power capacity. Recently, techniques for preparing surface coatings on cathode materials have been widely implemented as a measure to improve their stability, to enhance their electrochemical performance, and to prevent detrimental surface reactions between the electrode materials and electrolyte. This review will cover different types of surface coatings for cathode materials, as well as a comparison of the changes in electrochemical performance between those materials with and without an applied coating. In addition, a brief outlook is included for different cathode materials and their coatings.

Recently, the field of CO₂ electrolysis has experienced rapid scientific and technological progress. This review focuses specifically on the electrochemical conversion of CO₂ into carbon monoxide (CO), an important “building block” for the chemicals industry. CO₂ electrolysis technologies offer potentially carbon-neutral routes for the production of specialty and commodity chemicals. Many different technologies are actively being pursued. Electrochemical CO₂ reduction from aqueous solutions stems from the success of alkaline and polymer electrolyte membrane electrolyzers for water electrolysis and uses performance metrics established within the field of aqueous electrochemistry. High-temperature CO₂ electrolysis systems rely heavily on experience gained from developing molten carbonate and solid oxide fuel cells, where device performance is evaluated using very different parameters, commonly employed in solid-state electrochemistry. In this review, state-of-the-art low-temperature, molten carbonate, and solid oxide electrolyzers for the production of CO are reviewed, followed by a direct comparison of the three technologies using some of the most common figures of merit from each field. Based on the comparison, high-temperature electrolysis of CO₂ in solid oxide electrolysis cells seems to be a particularly attractive method for electrochemical CO production, owing to its high efficiency and proven durability, even at commercially relevant current densities.

Lithium-ion batteries can last many years but sometimes exhibit rapid, nonlinear degradation that severely limits battery lifetime. In this work, we review prior work on “knees” in lithium-ion battery aging trajectories. We first review definitions for knees and three classes of “internal state trajectories” (termed snowball, hidden, and threshold trajectories) that can cause a knee. We then discuss six knee “pathways”, including lithium plating, electrode saturation, resistance growth, electrolyte and additive depletion, percolation-limited connectivity, and mechanical deformation—some of which have internal state trajectories with signals that are electrochemically undetectable. We also identify key design and usage sensitivities for knees. Finally, we discuss challenges and opportunities for knee modeling and prediction. Our findings illustrate the complexity and subtlety of lithium-ion battery degradation and can aid both academic and industrial efforts to improve battery lifetime.

Single crystal Li[Ni_0.5Mn_0.3Co_0.2]O₂//graphite (NMC532) pouch cells with only sufficient graphite for operation to 3.80 V (rather than ≥4.2 V) were cycled with charging to either 3.65 V or 3.80 V to facilitate comparison with LiFePO₄//graphite (LFP) pouch cells on the grounds of similar maximum charging potential and similar negative electrode utilization. The NMC532 cells, when constructed with only sufficient graphite to be charged to 3.80 V, have an energy density that exceeds that of the LFP cells and a cycle-life that greatly exceeds that of the LFP cells at 40 °C, 55 °C and 70 °C. Excellent lifetime at high temperature is demonstrated with electrolytes that contain lithium bis(fluorosulfonyl)imide (LiFSI) salt, well beyond those provided by conventional LiPF₆ electrolytes. Ultra-high precision coulometry and electrochemical impedance spectroscopy are used to complement cycling results and investigate the reasons for the improved performance of the NMC cells. NMC cells, particularly those balanced and charged to 3.8 V, show better coulombic efficiency, less capacity fade and higher energy density compared to LFP cells and are projected to yield lifetimes approaching a century at 25 °C.

This paper studied the gases release of a graphite//NMC111(LiNi_1/3Mn_1/3Co_1/3O₂) cell during cycle in the voltage ranges of 2.6-4.2V and 2.6-4.8V and the temperatures of at 25°C and 60°C. It was proved that the CO₂, CO, and H₂ gases are released as a result of electrolyte decomposition. And it shows that the CO and H₂ gases evolution is a direct consequence of the electrochemical reaction of electrolyte decomposition, while the CO₂ generation is a consequence of the additional chemical reaction of interaction between the O₂ released from the cathode atomic lattice oxygen and CO released from the same place on the cathode (appearing because of the electrolyte decomposition). That is why at the same electrochemical reaction of electrolyte decomposition, the ratio CO₂/CO varies in the wide range from 0.82 to 2.42 depending on cycling conditions (temperature and cutoff voltage). It was proved that a potential-independent H₂ evolution is a consequence of its adsorption in pores of powdered graphite on anode. There was proposed the mechanism of the electrolyte decomposition and the gases evolution in lithium-ion cells at their cycling, which corresponds quantitatively to all obtained experimental results.

In this study, a one-step method was enforced for the phosphorylation of chitosan (CS) using ATMP, and later amino functionalized multiwalled carbon nanotubes (MWCNTs-NH₂) were used for the fabrication of PCS/N-MWCNTs membranes. The phosphorylation of CS and later PCS/N-MWCNTs nanocomposite membranes were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). They were also evaluated for their mechanical properties, water uptake, area swelling ratio, ion-exchange capacity (IEC), and proton conductivity. Interfacial interaction among an -NH₂ group of MWCNTs and -phosphonic acid as well as the -NH₂ group of PCS provided extra sites for proton transfer, thus improving the proton conductivity of PCS/N-MWCNTs membranes. These results revealed that the incorporation of N-MWCNTs into PCS chains lowers PCS chain mobility and ultimately improved the thermal and mechanical properties of the composite membranes. The proton conductivity of the composite membrane with 5 wt.% of N-MWCNTs at 80 °C was 0.045 S.cm⁻¹. Thus, PCS/N-MWCNTs nanocomposite membranes as a PEM can be used in fuel cells. With this advantage, the N-MWCNTs-filled hydrogen fuel cell outperforms compared to PCS filled membrane.

Copper (Cu) and stainless steel 316 L are widely used for biomedical applications, such as intrauterine devices and orthopedic/dental implants. Amino acids are abundantly present in biological environments. We investigated the influence of select amino acids on the corrosion of Cu under naturally aerated and deaerated conditions using a phosphate-free buffer. Amino acids increased the corrosion of Cu under both aeration conditions at pH 7.4. Cu release was also significantly (up to 18-fold) increased in the presence of amino acids, investigated at pH 7.4 and 37 °C for 24 h under naturally aerated conditions. Speciation modelling predicted a generally increased solubility of Cu in the presence of amino acids at pH 7.4. 316 L, investigated for metal release under similar conditions for comparison, released about 1,000-fold lower amounts of metals than did Cu and remained passive with no change in surface oxide composition or thickness. However, amino acids also increased the chromium release (up to 52-fold), significantly for lysine, and the iron release for cysteine, while nickel and molybdenum release remained unaffected. This was not predicted by solution speciation modelling. The surface analysis confirmed the adsorption of amino acids on 316 L and, to a lower extent, Cu coupons.

To improve power and cycling performance of lithium-ion batteries, dual-layer or porosity-gradient electrodes have been proposed. By engineering a higher porosity close to the separator, the intention is to improve ion transport where it is most impactful. In this research, MacMullin numbers of two dual-layer anode samples are tested using an impedance measurement technique developed previously. To characterize the microstructure of each layer independently, we developed an improved transmission-line model that accounts for each layer’s properties.Virtual experiments using COMSOL Multiphysics to simulate impedance measurements are used to examine and improve the accuracy of the numerical inversion procedure. The results for the two dual-layer anodes studied show that MacMullin numbers follow expected trends, though the anodes are quite different from each other.

In this study, the preparation of core/shell Ag@Fe₃O₄ nanoparticles (NPs) and its potential application toward highly sensitive electrochemical detection of furazolidone (FZD) have been reported. UV–visible spectroscopy, X-ray diffraction, scanning electron microscopy, and Zeta sizer are systematically carried out to confirm the formation, size distribution, and composition of Ag@Fe₃O₄ NPs. By computing the electrochemical characteristic parameters such as electrochemically active surface area (ECSA), electron-transfer resistance (R_ct), standard heterogeneous rate constant (k⁰), adsorption capacity (Γ), and electron transfer rate constant (k_s), the Ag@Fe₃O₄-modified electrode possessed remarkably enhanced electrochemical sensing performance for FZD determination compared to the unmodified screen-printed electrode (SPE). This enhancement of electrochemical activity can be attributed to the fast electron transfer kinetics and great adsorption capacity that arise from the synergistic coupling between the good electrical conductivity of the core AgNPs and the porosity of the protective Fe₃O₄ shell. Under optimum conditions, the Ag@Fe₃O₄-based electrochemical nanosensor exhibited not only high sensitivity toward FZD detection of 1.36 μA μM⁻¹ cm⁻² in the linear ranges from 0.5–15 μM and 15–100 μM, and low detection limit of 0.24 μM but also long-term stability, repeatability, and anti-interference ability. The applicability of the proposed sensing platform in honey and milk samples was also investigated.

Here we report an electrochemical sensor for the detection of epinephrine (EP) and serotonin (5-HT), two important neurotransmitters in the mammalian central nervous system, which are also present in serum. Their concentration will affect the psychological and physiological activities of the human body, especially in regulating emotions. Therefore, it is very important to detect EP and 5-HT simultaneously. Herein, cobalt nanoparticles (CoNPs) and melamine (MEL) were deposited on a glassy carbon electrode (GCE) by cyclic voltammetry (CV), resulting in an electrochemical sensor (MEL/CoNPs/GCE) that allowed the detection of both EP (0.23 V) and 5-HT (0.38 V vs. Ag/AgCl). Square wave voltammetry (SWV) measurements allowed us to establish a linear range of EP and 5-HT in the range of 5.00 to 500.00 μmol·l⁻¹, with a limit of detection of 1.60 μmol·l⁻¹ for EP, and of 2.52 μmol·l⁻¹ for 5-HT. The detection sensitivity were 1.38 and 1.62 μA·μM⁻¹·cm⁻² for EP and 5-HT. Finally, the sensor also was used to detect serum with a recovery of 92.8% to 98.2% for EP, 98.7% to 99.0% for 5-HT, with RSD of 3.3%, indicated that it can be used for the rapid and simultaneous detection of EP and 5-HT.

Electrification is seen as one of the key strategies to mitigate the growing energy demands in areas like transportation. With electrification, a better and safer energy storage system becomes a pressing need. Therefore, Li-based batteries are gaining popularity due to their high theoretical capacities. However, the use of Li-based batteries had been fraught with safety concerns. Specifically, Li dendrite formation during Li-plating can cause shorting in cells and thermal runaway. To that end, much effort has been put into mitigating the growth of these dendrites. To tackle this issue, the mechanisms involved in the formation of different morphologies of the plated Li is highlighted, as it determines, to a large extent, the mechanical properties of the plated Li. In turn, the mechanical properties of the plated Li will affect the cyclability and the overall safety of the battery. However, the yield strength of most materials used in separators and solid electrolytes are usually not high enough to prevent penetration by Li dendrites. Hence, various strategies to control the growth and morphology of Li deposits that can form dendrites, has been highlighted here as these strategies are key research directions for the advancement of high energy density Li-based batteries.

Several processes lead to a self-organization with a regular structure on a surface. Many systems are well understood and even applied in industry to create samples with unique material, optical, and electronic properties. However, the behavior of some systems is still surprising and the underlying atomic processes are still a mystery. The repetitive formation and lifting of chemical reactions, during oxidation, nitridization, or sulfidization, as well as surface- and binary-alloy formation, and the exchange process in electrochemical atomic layer deposition, leads to ordered nano-islands growth, although the reason is unknown. Here we show that only two ingredients are required leading to such a behavior. Firstly, the surface reaction/alloying exhibits a larger lattice constant than the original, clean surface, resulting in surface stress and atoms that are pushed out on top of the terrace. Secondly, upon restoration/reduction, these expelled atoms have problems finding back their original positions resulting in a flux of adatoms and vacancies per cycle. The peculiar “nucleation & growth” in these systems differs significantly from standard, well-established models and theories. A precursor phase nucleates and grows in the early stages of the reaction to build up the critical surface stress leading to the expelled adatoms. The system is structurally fully reversible upon restoration before this critical stress is reached. In the irreversible nucleation stage adatoms are created in between the precursor structure leading to the self-organization. Using the oxidation-reduction cycles on Pt(111) as an example, we explain all peculiar nucleation & growth aspects. The precursors are the so-called “place-exchange” atoms that form rows or spokes on the surface. The combination of simultaneous adatom and vacancy growth nicely describes the surface evolution: applying our new model to the experimental data fits the entire evolution over 170 cycles with only three fit parameters. Finally, we present an overview of other systems, all showing similar behavior, indicating the generality of the above described process.

Bibliometric methods are used to summarize literature on cathode electrocatalysts for Zn-air batteries published from 2007 to 2021 and analyze the characteristics and research trends of the published literature. From 2007 to 2013, the number of articles published every year has been tiny. From then to now, the number of papers published increased rapidly. According to statistics in the past six years, China has published the most significant number of articles, accounting for almost two-thirds of the total.

Hydrogen storage and production via electrochemistry using advanced amorphous metal catalysts with enhanced performance, cost, and durability may offer dynamic and intermittent power generation opportunities. As a new sub-class of materials, Pd-based metallic-glasses (MGs) have drawn intense attention because of their grain-free, randomly packed atomic structure with intrinsic chemical heterogeneity, bestowing unique physical, structural and chemical properties for energy applications. The first section of this review gives a general introduction to crystalline Pd and Pd-based MGs, including the fabrication techniques of MGs and their hydrogen applications. The second section is devoted to hydrogen sorption of Pd-based MGs examined under ribbons, nanowires/microrods, and thin-films subsections. Hydrogen evolution via Pd-based MGs is analyzed in the third section under the bulk rod, ribbons and thin-films subsections. The fourth section consists of hydrogenation kinetics and sensing, pseudocapacitance, and electron transfer kinetics subsections. The final section provides a broad summary of Pd-based metallic glasses and future prospects. Altogether, this review provides a thorough and inspirational overview of hydrogen sorption and evolution of Pd-based MGs targeted for future large-scale hydrogen energy storage and production systems.

Unwanted parasitic reactions in lithium-ion cells lead to self-discharge and inefficiency, especially at high temperatures. To understand the nature of those reactions this study investigates the open circuit storage losses of LFP/graphite and NMC811/graphite pouch cells with common alkyl carbonate electrolytes. The cells perform a storage test at 40 °C with a 500 h open circuit period after formation at temperatures between 40 °C and 70 °C. Cells formed at elevated temperature showed a high reversible storage loss that could be assigned to a redox shuttle generated in the electrolyte during formation. A voltage hold after formation can reduce the shuttle-induced self-discharge as indicated by significantly lower reversible storage losses, the absence of shuttling currents in cyclic voltammetry and improved metrics in ultra-high precision cycling. The addition of two weight percent vinylene carbonate can prevent redox shuttle generation and leads to almost zero reversible self-discharge.

This article has been written for students and teachers of the science and technology of low-temperature fuel cells, as well as for scientists and engineers actively involved in research and development in this area. It offers first an analysis of fuel cell electrocatalytic processes, identifying a common pattern in the mechanisms of these processes which serves as basis for a universal expression describing the non-linear V vs log J dependences observed under kinetic control. This analysis serves, in turn, as an introduction to reviews of several polymer electrolyte fuel cell technologies covering both science and engineering aspects and including process mechanisms and rate equations for the fuel cell electrode processes. These reviews highlight the requirement of explicit consideration of various types of overpotential-driven site activation steps in the analysis of experimentally observed V vs log J dependences. In addition to the mature technology of proton-conducting membrane fuel cells, the H₂/air and NH₃/air polymer electrolyte fuel cells using a hydroxide-ion conducting membrane as the electrolyte, are also discussed. Finally, a brief summary of remaining research and development needs and priorities is offered for each type of polymer electrolyte fuel cell discussed. This paper is a Critical Review in Electrochemical and Solid State Science and Technology (CRES³T).

Emphasis on clean energy has led to a widespread focus on lithium-ion batteries. However, a major obstacle is their degradation with several cycles or calendar aging. Battery Management System relies on an essential model-based algorithm to protect the battery from operating outside the safety limit. Thus, this work attempts to answer important research questions on battery models: (1) Are physics-based electrochemical models (EM) robust enough to identify internal cell degradation and abnormal battery behavior? (2) How are the structural simplifications and mathematical order reductions imposed on the EMs and what are their trade-offs? (3) How to apply simplified EM for safer and more efficient battery operation? (4) What are the prospects and obstacles of employing EM-based algorithms in the future? This paper presents a detailed analysis of EM from a modeling and application perspective. The paper introduces battery operating mechanisms, typical failures, and their effects. Followed by an analysis of full order EM (Pseudo 2-Dimensional), and further classification into simpler and advanced reduced-order models. The study demonstrates the gaps in theoretical understanding and their implementation for real-time battery operations such as in thermal management, energy utilization, and fault diagnosis and prognosis.

Lithium (Li) metal anodes are essential for developing next-generation high-energy-density batteries. However, Li dendrite/whisker formation caused short-circuiting issue and short cycle life have prevented lithium metal from being viably used in rechargeable batteries. Numerous works have been done to study how to regulate the Li growth in electrochemical cycling by using external stacking forces. While it is widely agreed that stack pressure positively affects the lithium plating/stripping process, the optimized pressure range provided by different works varies greatly because of the difference in the pressure control setup. In this work, a pressure control apparatus is designed for Li metal batteries with liquid and solid-state electrolytes (SSE). With considerations of minimizing cell to cell variation, a reusable split cell and pressure load cell are made for testing electrochemical cells with high precision pressure control. The capability of the designed setup is demonstrated by studying the pressure effect on the Li plating/stripping process.

Ternary metal halides A₃MX₆, (A = Li⁺, Na⁺; M = trivalent metal; X = halide) are a promising family of solid electrolytes for potential applications in all-solid-state batteries. Recent research efforts have demonstrated that chemical substitution at all three sites is an effective strategy to controlling battery-relevant material properties. The A₃MX₆ family exhibits a wide breadth of structure and anion sublattice types, making it worthwhile to comprehend how chemical substitutions manifest desirable functional properties including ion transport, electrochemical stability, and environmental tolerance. Yet, a cohesive understanding of the materials design principles for these substitutions have not yet been developed. Here, we bring together prior literature focused on chemical substitutions in the A₃MX₆ ternary metal halide solid electrolytes. Using materials chemistry perspectives and principles, we aim to provide insights into the relationships between crystal structure, choice of substituting ions and the extent of substitutions, ionic conductivity, and electrochemical stability. We further present targeted approaches to future substitution studies to enable transformative advances in A₃MX₆ solid electrolytes and all-solid-state batteries.

Active cathode material and graphite anode material are routinely mixed with conductor and binder to improve the electric conductivity and mechanical stability of electrodes. Despite its benefits, this carbon binder domain (CBD) impedes ionic transport and reduces the active surface area, thus impacting the battery performance. We consider a composite spherical particle, whose active-material core is coated with CBD, and its homogeneous counterpart, for which we derived equivalent electrical conductivity, ionic diffusivity, and reaction parameters in the Butler-Volmer equation. These equivalent characteristics are defined to ensure that the same mass and charge enter the composite and homogenized spheres. They are expressed in terms of the volume fraction of the active material and transport properties of the active material and CBD. In general, the equivalent effective diffusion coefficient and reaction parameters are time-dependent and exhibit two-stage behavior characterized by the reaction delay time. At later times, these characteristics are time-independent and given explicitly by closed-form formulae. The simplicity of these expressions facilitates their use in single- and multi-particle representations of Li-ion and Li-metal batteries.

Copper (Cu) and stainless steel 316 L are widely used for biomedical applications, such as intrauterine devices and orthopedic/dental implants. Amino acids are abundantly present in biological environments. We investigated the influence of select amino acids on the corrosion of Cu under naturally aerated and deaerated conditions using a phosphate-free buffer. Amino acids increased the corrosion of Cu under both aeration conditions at pH 7.4. Cu release was also significantly (up to 18-fold) increased in the presence of amino acids, investigated at pH 7.4 and 37 °C for 24 h under naturally aerated conditions. Speciation modelling predicted a generally increased solubility of Cu in the presence of amino acids at pH 7.4. 316 L, investigated for metal release under similar conditions for comparison, released about 1,000-fold lower amounts of metals than did Cu and remained passive with no change in surface oxide composition or thickness. However, amino acids also increased the chromium release (up to 52-fold), significantly for lysine, and the iron release for cysteine, while nickel and molybdenum release remained unaffected. This was not predicted by solution speciation modelling. The surface analysis confirmed the adsorption of amino acids on 316 L and, to a lower extent, Cu coupons.

Nickel manganese spinel LiNi0.5Mn1.5O4 is one of the most promising candidates for next-generation cobalt-free active materials for cathodes in lithium-ion batteries. Despite the relatively low specific capacity of 147 mAh/g, its high operating voltage of 4.7 V leads to a high specific energy of 690 Wh/kg. By extending operating voltage range from 3.0-4.9 V down to 1.5 V it is possible to access a lithiation degree up to x=2.5 and a theoretical specific capacity of 346 mAh/g. However, this causes pronounced capacity fading. Typical voltage profile show unexpected additional step at about 2.1 V, which cannot be explained by open-circuit measurements. We applied several electrochemical methods to investigate the lithiation of highly-ordered, stoichiometric spinel at low-voltages. Mixed potential measurements provided a comprehensive explanation for the low-voltage behaviour and supports interpretation of diffusion coefficients, rate capability tests, discharge at different temperatures and impedance spectroscopy. We show that anodic and cathodic partial reactions within the electrode can explain the presence of the additional 2.1 V step. This is caused by a kinetically-favoured formation of the phase Li2.5Ni0.5Mn1.5O4 and a simultaneous re-transformation to the thermodynamically stable phase Li2Ni0.5Mn1.5O4.

The effect of different positive supporting electrolytes on the performance of a bench-scale Zn-Ce redox flow battery (RFB) has been studied. The effectiveness of mixed methanesulfonic/sulfuric acid, mixed methanesulfonic/nitric acid, and pure methanesulfonic acid has been assessed and compared on the basis of the cyclic voltammetric response for the Ce(III)/Ce(IV) redox couple and galvanic charge-discharge of a bench-scale Zn-Ce RFB. The Ce(III)/Ce(IV) reaction exhibits faster kinetics and the RFB exhibits higher coulombic efficiency and long-term performance over ~40 charge-discharge cycles in the mixed 2 mol/L MSA–0.5 mol/L H₂SO₄ electrolyte compared to that achieved in the commonly used 4 mol/L MSA electrolyte due to lower H⁺ crossover and higher Ce(IV) solubility. The coulombic efficiency fade rate in the mixed MSA-H₂SO₄ electrolyte is 0.55% per cycle over 40 charge-discharge cycles, while the fade rate is 1.26% in the case of 4 mol/L MSA. Furthermore, the positive electrode reaction is no longer the limiting half-cell reaction even at the end of long-term battery charge-discharge operation. This work shows that a mixed MSA–H₂SO₄ acid electrolyte may be a better option for the positive side of a Zn-Ce RFB as a large-scale energy storage device.

We investigated the effect of platinum loading and layer thickness on cathode catalyst degradation by a comprehensive in-situ and scanning tunneling electron microscopy energy dispersive spectroscopy (STEM-EDS) characterization. To decouple the effect of platinum loading and layer thickness, the experiments were categorized in two sets, each with cathode loadings varying between 0.1 and 0.4 mgPt cm-2: (i) Samples with a constant Pt/C ratio and thus varying layer thickness, and (ii) samples with varying Pt/C ratios, achieved by dilution with bare carbon, to maintain a constant layer thickness at different platinum loadings. Every MEA was subjected to an accelerated stress test, where the cell was operated for 45,000 cycles between 0.6 and 0.95 V. Regardless of the Pt/C ratio, a higher relative loss in electrochemically active surface area was measured for lower Pt loadings. STEM-EDS measurements showed that Pt was mainly lost close to the cathode – membrane interface by the concentration driven Pt2+ ion flux into the membrane. The size of this Pt-depletion zone has shown to be independent on the overall Pt loading and layer thickness, hence causing higher relative Pt loss in low thickness electrodes, as the depletion zone accounts for a larger fraction of the catalyst layer

This article presents the development, parameterization, and experimental validation of a pseudo-three-dimensional multiphysics aging model of a 500 mAh high-energy lithium-ion cell with graphite anode and NMC cathode. This model includes electrochemical reactions for SEI formation at the graphite anode, lithium plating, and SEI formation on plated lithium. The thermodynamics of the aging reactions are modeled depending on temperature and ion concentration and the kinetics are described with an Arrhenius-type rate law. Good agreement of model predictions with galvanostatic charge/discharge measurements and electrochemical impedance spectroscopy is observed over a wide range of operating conditions. The model allows quantification of capacity loss due to cycling near beginning-of-life and visualization of aging colormaps as a function of operating conditions. The model predictions are also qualitatively verified through voltage relaxation, cell expansion, and cell cycling measurements. Based on this full model, six different aging indicators for determination of the limits of fast charging are derived from post-processing simulations of a reduced pseudo-two-dimensional isothermal model without aging mechanisms. The most successful indicator is based on combined plating and SEI kinetics calculated from battery states available in the reduced model. This methodology is applicable to standard pseudo-two-dimensional models available both commercially and as open source.

MEAs with nanofiber mat electrodes containing Pt/C catalyst and Nafion binder were fabricated and evaluated. The electrodes were prepared by electrospinning a solution of catalyst powder, salt-form Nafion (with Na⁺, Li⁺, or Cs⁺ as the sulfonic acid counterion), and a carrier polymer of either polyethylene oxide or poly(acrylic acid). The carrier polymer was extracted prior to MEA testing by a hot water soaking step. The resulting fibers were 15-17% porous, with a core-shell-like morphology (a coating of primarily Nafion on the fiber surface). MEAs with anode/cathode catalyst loadings of 0.1 mg_Pt/cm² each and a Nafion 211 membrane produced high power at both high and low relative humidity (RH) conditions in H2/air fuel cell tests, e.g., a maximum power density of 919 mW/cm² at 100% RH and 832 mW/cm² at 40% RH for a test at 80 °C and 200 kPa_abs. The presence of nm-size pores within the fibers trapped water via capillary condensation during low RH feed gas testing, thus maintaining a high proton conductivity of the Nafion binder in the anode and cathode while minimizing/eliminating ionic isolation of catalyst particles in low water content, poorly conductive binder.

We develop a coupled electrochemical-mechanical model to assess the current distributions at Li/single-ion conducting solid ceramic electrolyte interfaces containing a parameterized interfacial geometric asperity, and carefully distinguish between the thermodynamic and kinetic effects of interfacial mechanics on the current distribution. We find that with an elastic-perfectly plastic model for Li metal, and experimentally relevant mechanical initial and boundary conditions, the stress variations along the interface for experimentally relevant stack pressures and interfacial geometries are small (e.g., <1 MPa), resulting in a small or negligible influence of the interfacial mechanical state on the interfacial current distribution for both plating and stripping. However, we find that the current distribution is sensitive to interface geometry, with sharper (i.e., smaller tip radius of curvature) asperities experiencing greater current focusing. In addition, the effect on the current distribution of an identically sized lithium peak vs. valley geometry is not the same. These interfacial geometry effects may lead to void formation on both stripping and plating and at both Li peaks and valleys. The presence of high-curvature interface geometry asperities provides an additional perspective on the superior cycling performance of flat, film-based separators (e.g., sputtered LiPON) versus particle-based separators (e.g., polycrystalline LLZO) in some conditions.

The future of sustainable energy will consist of renewable energy integration with the critical enabler-energy storage technologies such as batteries. Specifically, redox flow batteries represent one type of grid-scale energy storage device with long life spans of at least 10 years and capabilities like peak shaving and load leveling. As more experimentalists are investigating the novel nonaqueous redox flow batteries (NRFBs) to achieve higher energy densities, there is a lack of mathematical models for NRFBs to understand the rate-limiting factors of the battery system. This paper is one of the first modeling efforts to understand key characteristics of NRFB system and operation with experimental validation. The model presented concludes that the nonaqueous solution (tetrabutylammonium vanadium(v) bis-hydroxyiminodiacetate and tetrabutylammonium vanadium(iv) bis-hydroxyiminodiacetate diluted in acetonitrile) is a promising half–cell solution for future redox flow battery couples. One key advantage for this half–cell is its generally facile reaction kinetics and insignificant activation losses. The real limiting factors for the half–cell are ohmic losses and mass transport losses with high sensitivities. Mass transport losses can be controlled by increasing concentrations of active species and staying within a SOC region of 10-90%.

Dual-carbon batteries (DCBs), in which both the positive and negative electrodes are composed of carbon-based materials, are promising next-generation batteries owing to their limited usage of scarce metals and high operating voltages. In typical DCBs, metal cations and anions in the electrolytes are consumed simultaneously at the negative and positive electrodes, respectively, which can rapidly deplete the charge carrier ions in the electrolytes. In this study, to solve this challenge, we focused on ionic liquids (ILs) as DCB electrolytes because they are solely composed of ions and are therefore intrinsically highly concentrated electrolytes. Charge–discharge behavior of the graphite positive electrodes was investigated in several IL electrolytes containing alkali metal cations (Li⁺, Na⁺, and K⁺) and amide anions (FSA⁻ and FTA⁻; FSA = bis(fluorosulfonyl)amide, FTA = (fluorosulfonyl)(trifluoromethylsulfonyl)amide). It was found that FTA-based ILs conferred superior cycling stability and higher capacities to graphite electrodes compared to FSA-based ILs, which was explained by the suppression of the corrosion of the aluminum current collector at high voltages. The highest reversible capacity of approximately 100 mAh g⁻¹ was obtained for the K-ion system using FTA-based ILs at 20 mA g⁻¹, which involved the formation of FTA–graphite intercalation compounds, as confirmed by ex-situ X-ray diffraction.

Activity and stability of electrodes with Pt and PtCo alloy catalysts supported on high surface area carbon, hereafter referred cto as a-Pt/C and d-PtCo/C, were evaluated for heavy-duty applications. Both catalysts had nearly identical Pt loading (50-wt% Pt on carbon and 0.25 mgPt/cm²) and had undergone thermal treatment to stabilize them by growing the average particle size to 4-5 nm. Both were subjected to 90,000 (90k) standard accelerated stress tests (AST) cycles consisting of 0.6-0.95 V square wave potentials, 3-s hold at upper and lower potential limits in H2/N2 at 1.5 atm, 80°C and 100% RH. Test protocols were developed to monitor the performance losses and characterize them in terms of activity for the oxygen reduction reaction (ORR), oxygen transport in the electrode and proton transport in the membrane and cathode catalyst layer. Despite the nearly double initial ORR activity, the PtCo/C electrode degraded faster due to the leaching of Co from the catalyst that had started even before the imposition of the AST potential cycles. Commensurate with Co leaching, Co poisoning of ionomer is responsible for the inferior performance of d-PtCo/C electrode at high current densities both before and after AST.