Journal of The Electrochemical Society

Presented here, is an extensive 35 parameter experimental data set of a cylindrical 21700 commercial cell (LGM50), for an electrochemical pseudo-two-dimensional (P2D) model. The experimental methodologies for tear-down and subsequent chemical, physical, electrochemical kinetics and thermodynamic analysis, and their accuracy and validity are discussed. Chemical analysis of the LGM50 cell shows that it is comprised of a NMC 811 positive electrode and bi-component Graphite-SiO_x negative electrode. The thermodynamic open circuit voltages (OCV) and lithium stoichiometry in the electrode are obtained using galvanostatic intermittent titration technique (GITT) in half cell and three-electrode full cell configurations. The activation energy and exchange current coefficient through electrochemical impedance spectroscopy (EIS) measurements. Apparent diffusion coefficients are estimated using the Sand equation on the voltage transient during the current pulse; an expansion factor was applied to the bi-component negative electrode data to reflect the average change in effective surface area during lithiation. The 35 parameters are applied within a P2D model to show the fit to experimental validation LGM50 cell discharge and relaxation voltage profiles at room temperature. The accuracy and validity of the processes and the techniques in the determination of these parameters are discussed, including opportunities for further modelling and data analysis improvements.

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 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.

Enhancing catalyst-layer efficiency and durability at high current densities is essential for scalable electrolyzer deployment. Unlike proton exchange membrane systems that are dominated by anodic losses, anion exchange membrane (AEM) systems can exhibit catalyst layer resistances at both electrodes, warranting the use of reference electrodes for kinetic decoupling. We present a methodology to quantify catalyst layer resistance, utilization heterogeneity, and transport limitations (ionic or electronic) by means of impedance diagnostics with dual reference electrodes integrated in the flow channels of each half-cell. Under nominal catalyst loading, we observed elevated local current densities near the membrane anode catalyst interface, implicating ionic conductivity as the primary cause. For the cathode, electronic resistance seems to be limiting. Combined, they manifest as an additional 50–80 mV overpotential attributable to the catalyst layer, a non-negligible fraction of the total 1.9 V of cell voltage at 2 A cm⁻². Reducing the catalyst loading improved the reaction homogeneity at the anode; however, for the cathode, it resulted in a marked decrease in effective electronic conductivity, which exacerbated the spatial heterogeneity and further elevated the cathodic kinetic overpotential. These findings highlight the need for designing and evaluating catalyst layer morphologies for balanced electrochemical activity and efficiency.

figure placeholder

The maximum energy that lithium-ion batteries can store decreases as they are used because of various irreversible degradation mechanisms. Many models of degradation have been proposed in the literature, sometimes with a small experimental data set for validation. However, a comprehensive comparison between different model predictions is lacking, making it difficult to select modelling approaches which can explain the degradation trends actually observed from data. Here, various degradation models from literature are implemented within a single particle model framework and their behavior is compared. It is shown that many different models can be fitted to a small experimental data set. The interactions between different models are simulated, showing how some of the models accelerate degradation in other models, altering the overall degradation trend. The effects of operating conditions on the various degradation models is simulated. This identifies which models are enhanced by which operating conditions and might therefore explain specific degradation trends observed in data. Finally, it is shown how a combination of different models is needed to capture different degradation trends observed in a large experimental data set. Vice versa, only a large data set enables to properly select the models which best explain the observed degradation.

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.

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.

Whilst extensive research has been conducted on the effects of temperature in lithium-ion batteries, mechanical effects have not received as much attention despite their importance. In this work, the stress response in electrode particles is investigated through a pseudo-2D model with mechanically coupled diffusion physics. This model can predict the voltage, temperature and thickness change for a lithium cobalt oxide-graphite pouch cell agreeing well with experimental results. Simulations show that the stress level is overestimated by up to 50% using the standard pseudo-2D model (without stress enhanced diffusion), and stresses can accelerate the diffusion in solid phases and increase the discharge cell capacity by 5.4%. The evolution of stresses inside electrode particles and the stress inhomogeneity through the battery electrode have been illustrated. The stress level is determined by the gradients of lithium concentration, and large stresses are generated at the electrode-separator interface when high C-rates are applied, e.g. fast charging. The results can explain the experimental results of particle fragmentation close to the separator and provide novel insights to understand the local aging behaviors of battery cells and to inform improved battery control algorithms for longer lifetimes.

A fundamental understanding of water and gas transport is crucial for continued improvements of electrolysis systems. This work demonstrates a technique to measure electro-osmotic drag in proton exchange membrane water electrolysis (PEMWE) cells. The method was validated using repeated testing of several variations of Nafion™ membranes. The effect of temperature, thickness, membrane fabrication route, current density, and equivalent weight on electro-osmotic drag coefficients were explored. Specific conclusions can be drawn from the data for this class of perfluorinated polymer membranes. Notably, temperature, membrane fabrication route, and equivalent weight were all found to have meaningful impact on electro-osmotic drag. The lowest electro-osmotic drag coefficients observed were just below 3 water molecules per proton and the highest electro-osmotic drag coefficients were just above 5 water molecules per proton. This represents up to a ∼70% increase in water flux and is expected to significantly impact hydrogen and oxygen flux across the cell. The observed electro-osmotic drag coefficients scaled proportionally to the water uptake of the membranes studied, with increased water uptake leading to higher electro-osmotic drag coefficients. Both the method of measuring electro-osmotic drag and the observed results in this paper are key findings that help quantify water flux in operating PEMWE cells.

figure placeholder

Battery performance is strongly correlated with electrode microstructural properties. Of the relevant properties, the tortuosity factor of the electrolyte transport paths through microstructure pores is important as it limits battery maximum charge/discharge rate, particularly for energy-dense thick electrodes. Tortuosity factor however, is difficult to precisely measure, and thus its estimation has been debated frequently in the literature. Herein, three independent approaches have been applied to quantify the tortuosity factor of lithium-ion battery electrodes. The first approach is a microstructure model based on three-dimensional geometries from X-ray computed tomography (CT) and stochastic reconstructions enhanced with computationally generated carbon/binder domain (CBD), as CT is often unable to resolve the CBD. The second approach uses a macro-homogeneous model to fit electrochemical data at several rates, providing a separate estimation of the tortuosity factor. The third approach experimentally measures tortuosity factor via symmetric cells employing a blocking electrolyte. Comparisons have been made across the three approaches for 14 graphite and nickel-manganese-cobalt oxide electrodes. Analysis suggests that if the tortuosity factor were characterized based on the active material skeleton only, the actual tortuosities would be 1.35–1.81 times higher for calendered electrodes. Correlations are provided for varying porosity, CBD phase interfacial arrangement and solid particle morphology.

Solid-state zinc-ion batteries (SSZIBs) offer intrinsic safety and low cost, yet their practical deployment is severely constrained by the low ionic conductivity and unstable Zn/electrolyte interfaces of existing solid polymer electrolytes. Herein, we report a composite polymer electrolyte with enhanced performance, fabricated by integrating ZIF-8@TiO₂ core–shell nanofillers into a PEO-PVDF matrix. The conformal TiO₂ shell reinforces the structural stability of ZIF-8 and establishes chemically robust polymer-filler interfaces, enabling interconnected Zn²⁺-preferential transport pathways within a mesoporous, cross-linked ion-conduction network. Benefiting from this synergistic architecture, the optimized LZPV-9 electrolyte delivers a high room-temperature ionic conductivity of 4.74 × 10^–4 S cm⁻¹, a Zn²⁺ transference number of 0.51, and stable cycling performance, retaining 88.37% of its initial capacity after 100 cycles. The Zn|LZPV-9|MnO₂ cell further achieves over 1000 h of stable plating/stripping at 0.2 mA·cm⁻² under ambient conditions without short circuit. This work demonstrates a nanoscale interfacial-engineering strategy to stabilize MOF-based fillers and provides a promising pathway toward durable, high-conductivity solid-state zinc-ion batteries.

figure placeholder

Highlights

• A nanoscale TiO₂ shell is engineered on ZIF-8 to stabilize the MOF structure and strengthen polymer–filler interfacial interactions.

• The composite electrolyte establishes a hierarchical Zn²⁺-transport network through synergistic chain-mobility enhancement and preserved MOF microporosity.

• PVDF-PEO crystallinity is effectively suppressed, enabling fast segmental dynamics and lowering the Zn²⁺ migration energy barrier.

• The optimized LZPV-9 electrolyte achieves high ionic conductivity (4.74 × 10^–4 S·cm⁻¹) and a large Zn²⁺ transference number (0.51) at room temperature.

• A Zn|LZPV-9|MnO₂ full cell delivers 88.37% capacity retention after 100 cycles, highlighting its potential for solid-state zinc-ion batteries.

Silicon is a promising anode material for next-generation lithium-ion batteries owing to its high theoretical capacity and natural abundance. However, its practical application is limited by the challenge of simultaneously achieving high specific capacity, low mechanical strain, and low cost. In this work, a composition-guided quantitative design strategy is proposed, in which the mass ratio of silicon to carbon nanofibres (Si/CNFs) is treated as a practical control parameter to balance capacity and volumetric expansion under realistic cost constraints. By systematically correlating component ratio, pore architecture, and electrode-level volumetric evolution, a practical CNFs content window of 14.3%–42.8% is identified, with compositions near 28.6% providing an optimal balance between active-material loading and strain buffering. A stepwise validation strategy is employed, in which nano-sized silicon is first used to elucidate the underlying mechanism, demonstrating that the optimized CNFs framework maintains structural integrity during cycling. This design concept is subsequently extended to micron-sized silicon, where the porous buffering reservoir effectively accommodates the severe volume changes of larger particles. As a demonstration of scalability, a composite electrode containing >70% micron-sized silicon delivers a reversible capacity of 1188 mAh g⁻¹ with 83% retention after 200 cycles, while limiting irreversible volumetric strain to below 10%.

figure placeholder

Highlights

• A quantitative strategy balances capacity, strain, and cost in Si anodes.

• Links component ratio to pore architecture and volumetric evolution.

• Stepwise validation bridges nano- and micron-silicon design principles.

• Porous buffering reservoir accommodates large-particle volume changes.

• Enables low-strain, high-energy, scalable silicon anode architectures.

The increasing adoption of electric vehicles intensifies the need for precise prognostics of lithium-ion battery capacity and end-of-life, but the task remains constrained due to aging mechanisms over time. To overcome these issues, this study presents PLS-Net, a Physics embedded LSTM Siamese Network that integrates domain knowledge with deep learning. As part of the feature extraction process, battery deterioration signals are analyzed to derive multivariate higher-order attributes and uses physics-based elements like resistance and capacity fading which serves as an input to PLS-Net. A Siamese architecture with cross-pair learning allows the network to simulate both self and cross battery interactions, increasing tolerance to data deficits. Unlike conventional models PLS-Net leverages both physical cognition and relational learning to make more accurate predictions. Experimental analysis on the NASA battery dataset shows that PLS-Net with limited historical samples starting from the 50th cycle of Battery B5, achieving a MSE of 3.73 × 10⁻⁵,  MAE of 0.0036, MAPE of 0.0025, and an R² score of 99.78%, validating PLS-Net as scalable and reliable framework for predictive battery management. Also, Explainable AI using SHAP values and latent embeddings shows that the model’s predictions are substantially impacted by critical degradation features, improves that interpretability and confidence in RUL estimations.

figure placeholder

Accurate capacity prediction is critical for lithium-ion battery health management in electric vehicles and energy storage systems. This study compares four machine learning methods for battery capacity estimation using the NASA Prognostics Center of Excellence dataset, including Optimized Random Forest, Least Squares Boosting, Lasso regression, and Ridge regression. Fourteen features were engineered from voltage, current, temperature, and electrochemical impedance measurements across 447 training cycles from three batteries, with validation on 132 cycles from an independent battery. All models were tuned using Leave-One-Battery-Out cross-validation with fold-specific normalization to ensure unbiased performance evaluation. The LSBoost model achieved the best performance with test RMSE of 0.0794 Ah, MAE of 0.0751 Ah, and R² of 0.7351, representing 12.2% improvement in RMSE compared to Optimized Random Forest and 13.6% improvement compared to linear baselines. Feature importance analysis using permutation methods identified cycle number as the dominant predictor followed by mean power and current variability, while partial dependence analysis revealed the marginal contribution of individual features to capacity estimation. The 4.92% mean absolute percentage error meets industrial requirements for battery management systems, establishing gradient boosting as an effective and computationally efficient methodology for state-of-health estimation in practical applications.

figure placeholder

Carbon-based electrodes with high specific capacitance and improved cyclability are crucial to increase the energy density of the electric double layer capacitor. However, many reported CFP-based electrodes still suffer from limited capacitance, poor cyclic stability, and complicated fabrication routes. Here, we report an electrode synthesized from a modified carbon fiber paper (CFP) that exhibits a high areal capacitance of 4.42 F cm⁻² (82.2 F cm⁻³) and a specific capacitance of 228 F g⁻¹ at a current density of 20 mA cm⁻² (1 A g⁻¹). The electrode is made by a two-step process that involves the anodization of CFP in nitric acid, followed by its deposition onto nickel foam. The impact of mass loading of anodized CFP on nickel foam has been studied and optimized. In contrast to most previous publications that are restricted to low mass loading (≺10 mg cm⁻²), the synthesized electrode exhibits exceptional capacitance performance even at elevated mass loading, highlighting its applicability for practical supercapacitor applications. A symmetric supercapacitor fabricated with the electrode exhibited an impressive specific energy of 15.6 Wh kg⁻¹. This work demonstrates a facile and scalable approach to developing high-performance CFP-based electrodes with improved practical applicability.

figure placeholder

Highlights

• High-loading NiCFP electrode shows 4.42 F cm⁻² and 228 F g⁻¹ capacitance.

• Two-step fabrication enables scalable high-capacitance carbon electrodes.

• Symmetric cell delivers high specific energy of 15.6 Wh kg⁻¹.

The development of batteries with new materials typically starts with small active material amounts and consequently with small cells, often with low-loaded electrodes. As development progresses to increasing technology readiness levels, mid-sized and large cells with thicker electrode coatings are mandatory. However, large cells have different electrochemical and physicochemical properties than small lab cells. Herein, we discuss similarities and especially differences in the behavior of small laboratory cells (e.g. coin) and larger cells (cylindrical, pouch, prismatic), regarding cell design, electrode thickness, specific energy on material and cell level, heating behavior due to current flow, impedance, voltage curves, and rate capability. Impedances at 1 kHz are reduced by three orders of magnitude from coin cells to large cells while heating power is increased by a factor of 10² to 10⁵. By comparing specific capacities on cathode material level with those on cell level for commercial cells, we find a reduction by a factor of ∼3 to ∼5, depending on the anode coating thickness. The large general gap from pure material to cell and between small laboratory, mid-sized, large pilot, and commercial cells need to be taken into account from the beginning of battery development to avoid potential misinterpretation.

figure placeholder

Highlights

• Differences between small lab cells, mid-sized, and large cells with increasing TRL

• Impedance decreases by three orders of magnitude from coin to large cells

• Heating power increases by a factor of 10² to 10⁵ from coin to large cells

• Specific capacities (material level) decrease by a factor of ∼3 to ∼5 (cell level)

• Differences must be considered to prevent misinterpretation of small cell results

Iodide-ion batteries have emerged as a prominent technology in the energy storage field due to their high theoretical capacity, high redox potential, inherent safety, environmental benignity, and low cost. However, the shuttle effect of polyiodides generated during cycling leads to active material loss, rapid capacity fade, and self-discharge. Furthermore, side reactions between these migrating species and the metal anode cause irreversible corrosion and passivation. To address these challenges, this review first details the working principles of iodide-ion batteries, with a specific focus on the reaction mechanisms within the cathode. It then systematically examines strategies to mitigate the shuttle effect across four key components—the cathode, anode, separator/interlayer, and electrolyte—in various iodide-ion battery systems. Finally, the review concludes by discussing future research directions based on current developments, aiming to guide further progress and pave the way for the large-scale application of this promising technology.

figure placeholder

Highlights

• The working principle of iodine-ion batteries.

• Improvement strategies for shuttle effect.

• Future outlook for iodine-ion batteries.

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder characterized by synaptic dysfunction, neuronal loss, and cognitive decline. Cumulative epidemiological and mechanistic evidence implicates chronic exposure to emerging contaminants, including phthalates, particulate matter, microplastics, and per- and polyfluoroalkyl substances, as modulators of AD pathogenesis. These pollutants can penetrate the blood–brain barrier and aggravate oxidative stress, neuroinflammation, and aberrant protein aggregation, thereby accelerating neurodegenerative cascades. The interplay between environmental risk factors and molecular hallmarks of AD underscores the urgent requirement for highly sensitive biosensing strategies capable of detecting early-stage biomarkers with diagnostic precision. Metal–organic frameworks (MOF), with their exceptional surface area, tunable porosity, and chemical modularity, provide a versatile platform for biomolecular recognition and signal amplification. Advanced MOF-based constructs, including AuNP-integrated MOF, MOF@MXene heterostructures, core–shell composites, and MOF–carbon quantum dot hybrids, have demonstrated enhanced electron transfer kinetics, superior biocompatibility, and robust signal transduction for detecting amyloid-β(Aβ) species, tau isoforms, and neurofilament light chain. This review systematically evaluates MOF-based biosensors’ structural-functional attributes for AD biomarker detection, delineates their current limitations, and proposes mechanistically informed design strategies to accelerate translation toward clinically viable, point-of-care diagnostic platforms in populations that are environmentally predisposed to AD.

figure placeholder

Cancer remains a leading global health challenge, with early detection critical in improving patient outcomes. Zinc oxide (ZnO) nanostructure-based biosensors have emerged as a promising solution due to their high sensitivity, biocompatibility, and flexible transduction mechanisms. This review highlights the recent advancements in ZnO biosensors for cancer detection, focusing on synthesis methods, biosensing mechanisms, and performance metrics. A solution-based and vapour-phase technique for fabricating ZnO nanostructures is compared, emphasising their effect on morphology, crystallinity, and sensing performance. Electrochemical, optical, and piezoelectric mechanisms are explored, showing ZnO’s ability to detect biomarkers such as CA-125, CYFRA 21–1, and sarcosine with ultra-low detection limits. Innovations in multimodal sensing and integration with portable platforms are discussed, along with challenges in stability, scale-up production, and clinical translation. The review concludes with recommendations for future directions, supporting the improvement of material engineering, point-of-care usage, and machine learning integration to advance ZnO-based biosensors for earlier cancer diagnosis. These developments hold great potential to transform cancer diagnostics, providing rapid, non-invasive, and low-cost solutions to global healthcare.

figure placeholder

Carbon compounds derived from biomass have some unique structural and compositional properties that have elicited a great deal of attention as potential catalysts for electrochemical applications. Among the myriad advantages they exhibit include their relatively low cost, environmental friendliness, accessibility, and renewable character. The biomass feedstocks of waste biomass and agricultural waste could be used for the production of carbon-based products in an eco-friendly and sustainable manner towards several electrocatalytic applications. Some of the newly developed electrocatalytic processes depend on such research, particularly the oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and the reduction of CO₂ nitrate/nitrite reduction,urea oxidation. This review mainly focuses on highlighting the synthesis techniques, structural characteristics, and electrochemical performance of biomass-derived carbon compounds to emphasize their potential as effective electrocatalysts. It underlines the function of carbon materials based on biomass doped with heteroatoms and carbon materials embellished with trace amounts of precious metals or transition metals, added to boost electrocatalytic activity. Further, the multifunctionality of biomass-derived materials is discussed thoroughly in this review article. Moreover, the status of current research, recent advances, and prospects of electrocatalysis by carbon materials obtained from biomass are outlined. It highlights how desirable it is to optimize these materials for applications that can efficiently and sustainably convert and store energy.

figure placeholder

Production of volatile fatty acids (VFAs) from biomass fermentation is a promising pathway for sustainable chemical production. A central challenge is cost-effective recovery and fractionation of VFAs from fermentation broths. Redox-mediated electrodialysis (redox-ED) can be an energy efficient technique for VFA separation, replacing water splitting with redox-reactions. However, the low selectivity between VFAs of different lengths (separation factors <3) obtained using commercially-available anion-exchange membranes limits the final product purity for industrial use. Cascaded operation can overcome these material limitations and increase product purity, yet multistage redox-ED can be complex and has not been extensively explored for selective ion separations. Here, we developed a physics-based model of redox-ED using finite elements to simulate the separation of a ternary carboxylic acid feed (propionic, butyric, and hexanoic) and evaluated five different multistage architectures including series, parallel, co-current, and counter-current setups. The single-stage, two-dimensional steady-state model captured the effect of the flow-field, concentration, and potential gradients, yielding reasonable agreement with experimental data. We then investigated the tradeoff between number of stages, product purity, and productivity, and assessed the impact of membrane selectivity. In sum, cascaded redox-ED with reflux simultaneously improved product purity and productivity, while series or equivalent single-stage architectures presented a tradeoff between VFA purity and productivity.

figure placeholder

Voltammetric measurements of electrochemical CO₂ reduction reaction (CO₂RR) selectivity on rotating ring disk electrodes (RRDE) are a rapid and sensitive method for quantifying an electrocatalyst’s selectivity, i.e. faradaic efficiency (FE). This method has been applied to polycrystalline Au electrocatalysts where a Au disk electrode catalyzes both the CO₂RR and hydrogen evolution reaction while the concentric Au ring electrode selectively senses CO by oxidizing CO back to CO₂. Such measurements enabled fundamental mechanistic studies but suffer from poor inter-laboratory reproducibility. This work identifies causes of variability in RRDE selectivity measurements by comparing protocols with different electrochemical methods, reagent purities, and glassware cleaning procedures. We observed FE_CO decrease by 56% during 5 min chronoamperometry measurements, a phenomenon that is not readily apparent in voltammetric scans due to their dynamic nature. Electroplating of electrolyte impurities onto the disk and ring surfaces were identified as a major contributor to Au deactivation. Additionally, the oxygen reduction reaction may lead to higher disk currents in inadequately purged electrolytes, causing an apparent underestimation of FE_CO at low overpotentials. Lastly, we propose operational bounds for CO₂RR selectivity measurements on Au using the RRDE method and provide suggestions on steps for improving the accuracy of this technique.

figure placeholder

This study explores chloride molten salt electrolysis (CMSE) as a promising route for energy-efficient iron metal (Fe) production. Moderate temperature (500 °C) LiCl-KCl molten salts offer excellent thermodynamic stability, high ionic conductivity and diffusivity, and high solubility for FeCl₃, thereby enabling efficient Fe metal extraction at high electrowinning rates. Here, we demonstrate the two essential steps for converting taconite ore into Fe metal. First, Fe₂O₃ from taconite pellets was selectively leached in HCl yielding a high-purity FeCl₃ aqueous solution, while the gangue components settled at the bottom. Then, anhydrous FeCl₃ was electrolyzed in a LiCl-KCl eutectic molten salt at 500 °C at high current density (1 A cm⁻²) and at high Coulombic efficiency (>85%). Analysis of the electrowon Fe deposits revealed dendritic structures with purity of >99 wt%, which could be further improved to nearly 100 wt% through arc re-melting. CMSE offers low specific energy consumption (3.7 kWhr kg⁻¹), competitive with H₂-DRI and other electrolytic approaches being pursued globally. Our findings underscore the potential of CMSE as an energy-efficient route for electrosynthesis of Fe metal.

Cathode-electrolyte interphase (CEI) is critical for inhibiting the cathode degradation to maintain cell life. However, the evolution of the CEI is still unclear due to its complex and slow dynamic process. Here we used scanning electrochemical microscopy (SECM) for in situ investigation of CEI formation process on LiFePO₄ cathode. Feedback images and probe scan curves showed a heterogeneous passivation that was gently generated on the LiFePO₄ particles during both charging and discharging. Besides, a LiFePO₄ composited electrode was also used to investigate the CEI formation to simulate the condition of real battery system. The composited cathode does not show obvious CEI formation within first two cycles. The SECM results between the pristine LiFePO₄ particles and the composited LiFePO₄ indicated the dynamic accumulation of CEI, which is influenced by the ability to charge transfer kinetics of cathode materials. This approach provided a feasible consideration for the connections between the dynamic evolution of the CEI and changes in charge transfer capability of cathode during cycling.

figure placeholder

Highlights

• In-situ investigation of cathode-electrolyte interphase formation.

• The evolution of native active material and composite slurry were compared.

• The electrochemical activity change upon cathode cycling are analysed in situ.

• The influence of the charge transfer capability upon CEI generation is revealed.

We revisit the classical derivation of the Butler-Volmer equation to include the effect of the electrode metal. If the metal is replaced by one with a different work function, keeping other conditions in the electrode constant, the chemical potential of electrons ${\mu }_e$ and the Galvani potential $\phi$ change in a complementary manner. Changes in ${\mu }_e$ and $\phi$ each impact the free energies of activation of the forward and backward electron transfer reactions, so we modify the classical expressions which relate them to applied voltage E by including also the effect of ${\mu }_e.$ Inserting these expressions in an Eyring-Polyani or Arrhenius type equation in the traditional way, we obtain a modified Butler-Volmer equation which expresses current density as a function of both $E$ and $\Delta {\mu }_e.$ The exchange current density $j_0$ appears as an exponential function of $\Delta {\mu }_e.$ For the work function $\Phi$ of the metal, the approximation $\Delta {\mu }_e\approx -F\Delta \Phi$ yields a linear relationship between $\ln j_0$ and $\Phi .$ The linear increase in $\ln j_0$ with $\Phi$ has long been reported. We show two experimental examples: the aqueous Fe²⁺/Fe³⁺ couple with positive slope and the hydrogen evolution reaction (HER) with parallel lines for the d and sp metals, both with positive slopes.

figure placeholder

Nickel-based ferrite composite coatings produced by electrodeposition have been extensively investigated for two primary application areas: magnetic functional coatings and electrocatalytic electrodes for water-splitting reac-tions. This review provides a comprehensive overview of the electrodeposition strategies employed to fabricate nickel-based ferrite composite coatings, focusing on the direct codeposition of pre-formed ferrite particles sus-pended in the electrolyte. The fundamental mechanisms governing particle codeposition are discussed in the con-text of classical and modern theoretical models. The structural, morphological, magnetic, and electrocatalytic properties of nickel-based ferrite composites are critically assessed, highlighting the influence of processing param-eters and microstructural features on functional performance. Particular attention is given to the quantification of ferrite incorporation, as many studies rely on qualitative characterization without reporting ferrite weight frac-tions, which limits meaningful comparison across reports. Finally, key gaps related to stability evaluation, corrosion behavior, and structure–processing–property relationships are identified, and future research directions aimed at enabling the rational design and advancement of nickel-based ferrite composite coatings are outlined.

Surface engineering of carbon electrodes can play a critical role in mitigating interfacial polarization and improving charge-transfer kinetics in aqueous organic redox flow batteries (AORFBs), yet the mechanistic understanding of electrode/electrolyte interactions remains limited. We demonstrate a rational approach to tune the interfacial electrochemical reactivity of graphite felt electrodes through grafting of diazonium salts bearing negatively charged functional groups. The modified surfaces exhibit enhanced hydrophilicity and increased electrochemical capacitance. The impact of surface charge on electron-transfer behavior was systematically investigated using both negatively and positively charged redox probes, revealing a strong dependence of electrochemical activity on electrostatic interactions. While grafted layers partially hindered the ferro/ferricyanide couple, they maintained the reversibility of the [Ru(NH3)6]3+/2+ system, confirming the charge-selective nature of the modified interfaces. When tested in neutral aqueous electrolytes containing nitroxide-based redox mediators, electrodes functionalized with sulfonate groups exhibited improved redox reversibility and reduced polarization. Flow battery tests using 4-OH-TEMPO electrolytes demonstrated up to 15% greater capacity and reduced polarization losses compared to pristine electrodes, particularly at high current densities. These findings establish diazonium chemistry as a versatile and controllable route to tailor electrode/electrolyte interactions in RFBs.

Bisphenol A (BPA) is an industrial chemical and emerging environmental contaminant whose presence in water and food at low concentrations poses health risks. Here, we developed a hybrid nanocomposite electrode combining cetyltrimethylammonium bromide–incorporated silica (CTAB@SiO2) and 3-aminopropyltriethoxysilane (APTES)-modified multi-walled carbon nanotubes (MWCNTs) for electrochemical BPA detection. CTAB@SiO2 provides a porous, positively charged matrix to enhance BPA adsorption and preconcentration, while APTES-functionalized MWCNTs ensure efficient electron transport and structural stability on a glassy carbon electrode. The sensor exhibits enhanced voltammetric response, which is consistent with adsorption-assisted accumulation and increased electroactive surface area. Under optimized conditions, three distinct linear ranges were obtained (1.5 × 10-9–1 × 10-8 M, 1 × 10-8–1 × 10-7 M, and 1 × 10-7–1 × 10-6 M), reflecting adsorption-controlled, mixed adsorption–diffusion, and diffusion-controlled regimes, respectively, with a detection limit of 1.2 × 10-9 M (S/N = 3) and a sensitivity (up to 3.13 × 108 A•M-1•cm-2 in the ultra-trace range). The electrode demonstrated good repeatability, selectivity, and stability, with recoveries in spiked environmental and food samples ranging from 96.0% to 102.4%. These results results highlight CTAB@SiO2@MWCNT–APTES as an adsorption-enhanced platform for BPA monitoring, while further validation in naturally contaminated samples is needed to confirm ultra-trace performance.

In this study, we examined the corrosion resistance of Ru₅₇Mo_14.25W_23.75Fe₅, Ru₅₄Mo_13.5W_22.5Fe₁₀, and Ru₄₈Mo₁₂W₂₀Fe₂₀ alloys in inorganic acids. The alloys were fabricated using the dewetting micro-pulling-down and plasma-melt stamping methods. Immersion tests in H₂SO₄ at 300 °C for 24 h indicated that Ru-Mo-W-Fe alloys exhibit better corrosion resistance (<0.17 mm/y), compared to conventional corrosion-resistant materials (>10 mm/y). Immersion tests at 25 °C in 5% HCl for 72 h and at 100 °C in 50% HF for 24 h also indicated that Ru-Mo-W-Fe alloys are highly corrosion resistant. Electrochemical tests in 1 M HCl and 1M H₂SO₄ revealed an increase in the anodic current and the formation of a low charge transfer resistance passive layer corresponding to alloying Fe. XPS analysis revealed that the primary corrosion product formed during polarization of Ru-Mo-W-Fe alloys in 1M H₂SO₄ was WO₃. Notably, WO₃ is kept passivated on pure W during the corrosion in H₂SO₄; however, it is not kept passivated when present on Ru-Mo-W-Fe alloys.

Toxic organic dyes pose a significant ecological risk when released into the environment. Monitoring the concentration of these dyes in wastewater is crucial for preventing pollution and protecting the environment. One of the best electrochemical methods for identifying organic dyes is cyclic voltammetry (CV). Metal oxides, metal nanoparticles, nanocarbon materials, surfactants, and polymer-modified carbon paste electrodes (MCPE) have been reported to detect various organic dyes; nevertheless, their capacity to do so is limited by the specific redox potentials. Nowadays, various alloys are extensively used to determine different organic dyes, and among them, high entropy alloys (HEAs) stand out as the best modifiers. This is because HEAs are composed of at least five different elements, each of which has a unique redox potential; they have large and distinctive redox potentials. Thus, the use of HEA modified carbon paste electrodes (HEA-MCPE) is more advantageous than other MCPEs. The porosity and the surface area of the HEAs are further improved by the mechanical alloying process. The prepared electrode has shown significant electrocatalytic properties, and therefore, in the present article, we have discussed the benefits, challenges, and applications of HEA-MCPEs for the electrochemical detection of organic dyes.

Nickel-based ferrite composite coatings produced by electrodeposition have been extensively investigated for two primary application areas: magnetic functional coatings and electrocatalytic electrodes for water-splitting reac-tions. This review provides a comprehensive overview of the electrodeposition strategies employed to fabricate nickel-based ferrite composite coatings, focusing on the direct codeposition of pre-formed ferrite particles sus-pended in the electrolyte. The fundamental mechanisms governing particle codeposition are discussed in the con-text of classical and modern theoretical models. The structural, morphological, magnetic, and electrocatalytic properties of nickel-based ferrite composites are critically assessed, highlighting the influence of processing param-eters and microstructural features on functional performance. Particular attention is given to the quantification of ferrite incorporation, as many studies rely on qualitative characterization without reporting ferrite weight frac-tions, which limits meaningful comparison across reports. Finally, key gaps related to stability evaluation, corrosion behavior, and structure–processing–property relationships are identified, and future research directions aimed at enabling the rational design and advancement of nickel-based ferrite composite coatings are outlined.

Silicon–graphite blend electrodes offer higher specific capacity than pure graphite and are increasingly used in high-energy lithium-ion batteries. This study proposes and validates a method to predict the heat generation in such blends under low-rate cycling conditions. The heat flow of individual silicon and graphite electrodes is measured using isothermal micro-calorimetry, while their pseudo-open-circuit potentials are recorded. The single-component data was combined to calculate blend potential, current distribution, and total heat generation across various silicon-to-graphite ratios. Three blend electrodes with different amounts of nanometer-sized silicon were fabricated for validation. In addition, a dual calorimetric setup was developed to simultaneously measure the current and the heat flow contributions from both active material components during cycling. The calculated electrochemical and thermal behavior were in good agreement with the experimental data, confirming that heat generation in silicon–graphite blends can be predicted using a linear combination of individual component contributions. This supports the applicability of the rule of mixtures under low-rate conditions. The proposed method enables accurate prediction of blend electrode thermal behavior based solely on single-component data, reducing the need to fabricate blend electrodes. In addition, the dual calorimeter setup provides a new tool for decoupling component-specific heat contributions in composite electrodes.

figure placeholder

Transmission line models (TLMs) are finite algebraic representations of porous electrodes, providing extraordinary flexibility to include materials physics that makes traditional porous electrode analysis intractable. We provide an algebraic framework for extending traditional linear TLMs to second harmonic nonlinear TLMs (2nd-nTLMs) and validate it against analytical porous electrode theory developed previously. To demonstrate the flexibility of 2nd-nTLMs, we introduce core–shell particles (common in batteries) into the porous electrode and explore the EIS and 2nd-NLEIS response. The ability of half-cell 2nd-NLEIS to discriminate among models is explored using TLMs and 2nd-nTLMs with core–shell structured particles (along with diffusion impedance) under the limit of high solid conductivity compared to electrolyte conductivity. The 2nd-NLEIS response is shown to amplify small parameters differences under conditions where EIS is insensitive. Parameter identifiability is further evaluated for identical and overlapping RC time constants in the core and shell by curve fitting with a single RC time constant model. While simultaneous EIS and 2nd-NLEIS analysis cannot discern homogeneous or core–shell particles in the limiting case of identical RC time constants, it can identify inapplicable models where the EIS spectrum is well fit but not the 2nd-NLEIS spectrum, even with overlapping time constants.

figure placeholder

Medium-nickel layered oxide (NMC) materials are widely adopted by cell manufacturers, as they provide higher energy density without compromising safety at high voltage. However, challenges such as poor rate capability and limited lifetime at higher cutoff voltages still hinder their broader application. Our analysis of vendor materials revealed that, among the multiple additives used to enhance performance, cobalt is also employed as a surface coating element by some vendors. This study demonstrates a simple process to achieve a cobalt-rich surface on the NMC cathode via an all-dry synthesis method, verified by X-ray Photoelectron Spectroscopy (XPS). Our Co-coated NMC samples achieve performance close to that of top-tier vendor samples that incorporate multiple coating additives. Transmission electron microscopy (TEM) further confirms the incorporation of cobalt on the surface of single-crystal Li_1+x(Ni_0.6Mn_0.4)_1-xO₂. This work highlights the importance of a cobalt-rich surface, showing that minimal cobalt addition can significantly improve electrochemical performance at high cutoff voltages without requiring numerous additives.

figure placeholder

Understanding the origins of the excellent H-barrier performance of Zn coatings is essential for optimizing their use as coatings on high strength steels and performance in various H-containing environments. We compare H-trapping energies associated with point defects in the metals Al, Cu, Ni, Pd, Cr, Fe, V, Mg, Ti, and Zn. Zn shows exceptionally weak interaction with H, with trapping energies ranging from 0.19 to 1.20 eV/at, far from the threshold of −0.6216 eV/at for irreversible trapping. Al and Mg also have low H-affinities, while Ti shows the strongest H-affinity. Band-structure projections reveal that all metals except Zn and Al form a localized Hmetal hybrid band, indicating that an available d-band is critical for strong H-bonding. In Zn, the fully filled d-band lies too low in energy to contribute to H bonding, explaining its low H-trapping energies. The d-band center position correlates with the trapping energies in different defect configurations. ZnO provides a more favorable site for H than metallic Zn, suggesting enhanced diffusion along partially oxidized grain boundaries. Stronger trapping at Zn/Al₂O₃, Zn/Fe, and Zn/ZnO interfaces also has implications for electroplating, where H generated during deposition may become immobilized at such interfaces, reducing the effectiveness of post-deposition bake-out treatments.

figure placeholder

Highlights

• H-trapping energies at different defects were investigated in 10 metals.

• Zn shows the least attraction to H among the investigated metals.

• Zn interfaces with ZnO, Fe, and Al₂O₃ provide moderate to strong trapping sites.

• Other d metals show a localized bond with H in band structure, whereas Zn does not.

• The d-band of Zn lies energetically too low to interact with H.

This study presents post-mortem analyses of polymer electrolyte membrane fuel cell (PEMFC) stacks operated using previously published accelerated durability test (ADT) protocols. Each ADT, lasting 1,200 h, was derived from a 5,500 h automotive-relevant reference test and designed to isolate the effects of load cycling, operating temperature, and humidity cycling. All major membrane electrode assembly components, the membrane, catalyst layers, and gas diffusion layers (GDL), were characterized using SEM, EDX, IR thermography, contact angle measurements and XPS, and the results then correlated with prior in situ diagnostics. Elevated temperature and humidity cycling were identified as the most detrimental stressors under system-relevant operating conditions that included voltage clipping at 850 mV. These conditions led to accelerated carbon corrosion, increased platinum dissolution and cobalt leaching in the cathode catalyst layer, as well as a significant loss of hydrophobicity in the GDL. The membrane remained structurally stable, although localized stress indicators were observed. The results confirm that the applied ADT protocols successfully reproduce realistic degradation patterns and enable a differentiated assessment of stressor-specific aging phenomena. This provides a robust basis for refining accelerated stack testing methodologies and optimizing operating conditions for improved PEMFC stack durability.

figure placeholder

Green hydrogen, produced through water electrolysis, is a key enabler of a low-carbon energy future, and anion exchange membrane electrolyzers (AEMELs) have emerged as a promising technology due to their potential for ultra-low-cost operation. However, achieving low cell voltage at high current densities and maintaining long-term durability remain key AEMEL challenges. To address these issues, most research efforts to date have focused on developing advanced catalysts and membranes. In contrast, the influence of non-material factors, such as cell assembly parameters and operating conditions, remains underexplored, even though they can significantly impact performance. This study investigates how such variables affect AEMEL cell voltage and durability, using commercially available Aemion⁺® membranes and ionomers. Cell assembly parameters, including electrode pre-treatment, membrane thickness, cell hardware, and membrane–electrode assembly (MEA) compression, were evaluated alongside key operating conditions such as flow configuration and heating mode. These parameters are shown to have a significant influence on in-cell phenomena, including electrochemical reactions, water and gas transport, and thermal distribution, as well as critical in-cell properties such as electrode–membrane adhesion, interfacial resistance, electrical conductivity, porosity of the catalyst layer, and polymer swelling or shrinkage. A systematic investigation of these factors showed that their careful optimization can lead to substantial reductions in operating voltage, up to 360 mV at 1.0 A cm⁻², without any changes to the catalyst or membrane chemistry. These findings offer new insights into practical strategies for improving AEM electrolyzer performance and highlight the importance of considering engineering and operational design parameters alongside material innovations for commercial viability.

figure placeholder

Highlights

• Systematic optimization of AEM electrolyzer cell assembly and operating conditions

• 360 mV reduction in operating voltage at 1.0 A cm⁻² without changing the catalyst or membrane

• Practical design guidance is provided for scalable AEM electrolyzer performance improvement

• Strategies can be adopted to create standardized testing conditions for research environments

Sodium-ion batteries (SIBs) are promising alternatives to lithium-ion batteries (LIBs) for low-temperature applications, owing to sodium’s lower desolvation energy compared to lithium. The crystal structure of the cathode active material determines the kinetics and transport properties of the cathode and can have a significant influence on the low temperature operation of SIBs. In this study, the performance of sodium layered (Na_2/3Fe_1/2Mn_1/2O₂, or NFMO) and channel-type cathodes (Na_0.44MnO₂, or NMO) at varying temperatures is investigated through electrochemical cycling, cyclic voltammetry, and electrochemical impedance spectroscopy. NMO, although having a lower initial capacity, demonstrates better capacity retention and more stable charge transfer kinetics at low temperatures. The lattice changes and relatively stable phases correlate with the electrochemical data, suggesting superior performance of channel-type NMO at lower temperatures. This indicates that the channel-type sodium cathode structure is more suitable for applications demanding stable performance at low-temperature conditions.

figure placeholder

The development of batteries with new materials typically starts with small active material amounts and consequently with small cells, often with low-loaded electrodes. As development progresses to increasing technology readiness levels, mid-sized and large cells with thicker electrode coatings are mandatory. However, large cells have different electrochemical and physicochemical properties than small lab cells. Herein, we discuss similarities and especially differences in the behavior of small laboratory cells (e.g. coin) and larger cells (cylindrical, pouch, prismatic), regarding cell design, electrode thickness, specific energy on material and cell level, heating behavior due to current flow, impedance, voltage curves, and rate capability. Impedances at 1 kHz are reduced by three orders of magnitude from coin cells to large cells while heating power is increased by a factor of 10² to 10⁵. By comparing specific capacities on cathode material level with those on cell level for commercial cells, we find a reduction by a factor of ∼3 to ∼5, depending on the anode coating thickness. The large general gap from pure material to cell and between small laboratory, mid-sized, large pilot, and commercial cells need to be taken into account from the beginning of battery development to avoid potential misinterpretation.

figure placeholder

Highlights

• Differences between small lab cells, mid-sized, and large cells with increasing TRL

• Impedance decreases by three orders of magnitude from coin to large cells

• Heating power increases by a factor of 10² to 10⁵ from coin to large cells

• Specific capacities (material level) decrease by a factor of ∼3 to ∼5 (cell level)

• Differences must be considered to prevent misinterpretation of small cell results

Carbon fiber structural battery electrodes combine load-bearing capacity with electrochemical energy storage. The fiber-matrix interface plays a critical role by enabling load transfer through adhesion while also providing electrochemically active surface area for intercalation reactions. However, fiber-matrix interface debonding can compromise structural integrity and affect electrochemical performance, and it is therefore essential to understand for structural energy storage design. This work employs a three-dimensional (3D) model to investigate interfacial behavior under galvanostatic cycling and constant mechanical loading, applied both along the longitudinal and transverse electrode directions. The interfacial damage is predicted under these conditions and the resulting impact on multifunctional performance is evaluated considering two-phase and homogeneous structural battery electrolyte (SBE) matrices. The 3D analysis captures the interfacial response at the fiber ends, often overlooked in two-dimensional models. In addition, the influence of lithium concentration-dependent fiber properties on the electrode’s mechanical and electrochemical response is quantified. Lithiation-induced fiber expansion and transverse tensile loading localize interfacial stresses near the fiber ends, promoting fiber-matrix debonding, while longitudinal tensile loading has minimal or even suppressive effects on debonding. Interfacial debonding enhances electrochemical performance in two-phase matrices through increased fiber-electrolyte contact and degrades electrochemical performance in homogeneous matrices by reducing fiber-electrolyte contact.

figure placeholder

Highlights

• Electrode behavior is investigated under electrochemical and mechanical loading.

• Fiber-matrix debonding is predicted with a cohesive zone model.

• Effect of lithium concentration-dependent fiber properties is analyzed.

• Debonding reduces electrode load-bearing capacity.

• Effects of debonding on electrochemical performance differ by SBE matrix type.

We compare the adsorption energies calculated by Nørskov et al. with data derived from experimental values; except for Ni and Co, which absorb hydrogen strongly, there is a linear relation. We discuss the model proposed by these authors in the light of extensive previous work and of experimental data and find it overly simplistic.

A density functional theory database of hydrogen chemisorption energies on close packed surfaces of a number of transition and noble metals is presented. The bond energies are used to understand the trends in the exchange current for hydrogen evolution. A volcano curve is obtained when measured exchange currents are plotted as a function of the calculated hydrogen adsorption energies and a simple kinetic model is developed to understand the origin of the volcano. The volcano curve is also consistent with Pt being the most efficient electrocatalyst for hydrogen evolution. © 2005 The Electrochemical Society. All rights reserved.

The Solid-Electrolyte-Interphase (SEI) model for non-aqueous alkali-metal batteries constitutes a paradigm change in the understanding of lithium batteries and has thus enabled the development of safer, durable, higher-power and lower-cost lithium batteries for portable and EV applications. Prior to the publication of the SEI model (1979), researchers used the Butler-Volmer equation, in which a direct electron transfer from the electrode to lithium cations in the solution is assumed. The SEI model proved that this is a mistaken concept and that, in practice, the transfer of electrons from the electrode to the solution in a lithium battery, must be prevented, since it will result in fast self-discharge of the active materials and poor battery performance. This model provides [E. Peled, in “Lithium Batteries,” J.P. Gabano (ed), Academic Press, (1983), E. Peled, J. Electrochem. Soc., 126, 2047 (1979).] new equations for: electrode kinetics (i_o and b), anode corrosion, SEI resistivity and growth rate and irreversible capacity loss of lithium-ion batteries. This model became a cornerstone in the science and technology of lithium batteries. This paper reviews the past, present and the future of SEI batteries.

Electrochemical techniques have been used to study the reversible insertion of sodium into hard‐carbon host structures at room temperature. In this paper we compare these results with those for lithium insertion in the same materials and demonstrate the presence of similar alkali metal insertion mechanisms in both cases. Despite the gravimetric capacities being lower for sodium than lithium insertion, we have achieved a reversible sodium capacity of 300 mAh/g, close to that for lithium insertion in graphitic carbon anode materials. Such materials may therefore be useful as anodes in rechargeable sodium‐ion batteries. © 2000 The Electrochemical Society. All rights reserved.

Layered LiNi_xMn_yCo_zO₂ (NMC) is a widely used class of cathode materials with LiNi_1/3Mn_1/3Co_1/3O₂ (NMC111) being the most common representative. However, Ni-rich NMCs are more and more in the focus of current research due to their higher specific capacity and energy. In this work we will compare LiNi_1/3Mn_1/3Co_1/3O₂ (NMC111), LiNi_0.6Mn_0.2Co_0.2O₂ (NMC622), and LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) with respect to their cycling stability in NMC-graphite full-cells at different end-of-charge potentials. It will be shown that stable cycling is possible up to 4.4 V for NMC111 and NMC622 and only up to 4.0 V for NMC811. At higher potentials, significant capacity fading was observed, which was traced back to an increase in the polarization of the NMC electrode, contrary to the nearly constant polarization of the graphite electrode. Furthermore, we show that the increase in the polarization occurs when the NMC materials are cycled up to a high-voltage feature in the dq/dV plot, which occurs at ∼4.7 V vs. Li/Li⁺ for NMC111 and NMC622 and at ∼4.3 V vs. Li/Li⁺ for NMC811. For the latter material, this feature corresponds to the H2 → H3 phase transition. Contrary to the common understanding that the electrochemical oxidation of carbonate electrolytes causes the CO₂ and CO evolution at potentials above 4.7 V vs. Li/Li⁺, we believe that the observed CO₂ and CO are mainly due to the chemical reaction of reactive lattice oxygen with the electrolyte. This hypothesis is based on gas analysis using On-line Electrochemical Mass Spectrometry (OEMS), by which we prove that all three materials release oxygen from the particle surface and that the oxygen evolution coincides with the onset of CO₂ and CO evolution. Interestingly, the onsets of oxygen evolution for the different NMCs correlate well with the high-voltage redox feature at ∼4.7 V vs. Li/Li⁺ for NMC111 and NMC622 as well as at ∼4.3 V vs. Li/Li⁺ for NMC811. To support this hypothesis, we show that no CO₂ or CO is evolved for the LiNi_0.43Mn_1.57O₄ (LNMO) spinel up to 5 V vs. Li/Li⁺, consistent with the absence of oxygen release. Lastly, we demonstrate by the use of ¹³C labeled conductive carbon that it is the electrolyte rather than the conductive carbon which is oxidized by the released lattice oxygen. Taking these findings into consideration, a mechanism is proposed for the reaction of released lattice oxygen with ethylene carbonate yielding CO₂, CO, and H₂O.

Lithium-ion batteries are well-suited for fully electric and hybrid electric vehicles due to their high specific energy and energy density relative to other rechargeable cell chemistries. However, these batteries have not been widely deployed commercially in these vehicles yet due to safety, cost, and poor low temperature performance, which are all challenges related to battery thermal management. In this paper, a critical review of the available literature on the major thermal issues for lithium-ion batteries is presented. Specific attention is paid to the effects of temperature and thermal management on capacity/power fade, thermal runaway, and pack electrical imbalance and to the performance of lithium-ion cells at cold temperatures. Furthermore, insights gained from previous experimental and modeling investigations are elucidated. These include the need for more accurate heat generation measurements, improved modeling of the heat generation rate, and clarity in the relative magnitudes of the various thermal effects observed at high charge and discharge rates seen in electric vehicle applications. From an analysis of the literature, the requirements for lithium-ion thermal management systems for optimal performance in these applications are suggested, and it is clear that no existing thermal management strategy or technology meets all these requirements.

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.

Past theories of electrode stability assume that the surface tension resists the amplification of surface roughness at cathodes and show that instability at lithium/liquid interfaces cannot be prevented by surface forces alone [Electrochim. Acta, 40, 599 (1995)]. This work treats interfacial stability in lithium/polymer systems where the electrolyte is solid. Linear elasticity theory is employed to compute the additional effect of bulk mechanical forces on electrode stability. The lithium and polymer are treated as Hookean elastic materials, characterized by their shear moduli and Poisson’s ratios. Two-dimensional displacement distributions that satisfy force balances across a periodically deforming interface are derived; these allow computation of the stress and surface-tension forces. The incorporation of elastic effects into a kinetic model demonstrates regimes of electrolyte mechanical properties where amplification of surface roughness can be inhibited. For a polymer material with Poisson’s ratio similar to poly(ethylene oxide), interfacial roughening is mechanically suppressed when the separator shear modulus is about twice that of lithium. © 2005 The Electrochemical Society. All rights reserved.

The conventional LiPF₆/carbonate-based electrolytes have been widely used in graphite (Gr)-based lithium (Li) ion batteries (LIBs) for more than 30 years because a stable solid electrolyte interphase (SEI) layer forms on the graphite surface and enables its long-term cycling stability. However, few of these electrolytes are stable under the more stringent conditions needed with a Li metal anode (LMA) and other anodes, such as silicon (Si), which exhibit large volume changes during charge/discharge processes. Many different approaches have been developed lately to stabilize Li metal batteries (LMBs) and Si-based LIBs. From this aspect, localized high-concentration electrolytes (LHCEs) have unique advantages: not only are they stable in a wide electrochemical window, they can also form stable SEI layers on LMA and Si anode surfaces to enable their long-term cycling stability. The ultrathin SEI layer formed on a Gr anode can also improve the safety and high-rate operation of conventional LIBs. In this paper, we give a brief summary of our recent work on LHCEs, including their design principle and applications in both LMBs and LIBs. A perspective on the future development of LHCEs is also discussed.

In this paper, we compare the interactions of lithium and sodium with a range of carbon materials in electrochemical cells. Through wide angle in situ X-ray scattering studies, we demonstrate that both lithium and sodium can be inserted into the interlayer space in disordered carbon materials. This insertion process is accompanied by an increase in the interlayer spacing in these materials. Small-angle in situ scattering studies are presented to clearly show the insertion of lithium and sodium into nanopores within disordered hard carbons. We also show that very little, if any, sodium can be inserted into graphitic materials in contrast to the large capacity seen for lithium insertion. © 2001 The Electrochemical Society. All rights reserved.