Journal of The Electrochemical Society

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

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.

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.

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.

Reversible extraction of lithium from ${\mathrm{LiFePO}}_4$ (triphylite) and insertion of lithium into ${\mathrm{FePO}}_4$ at 3.5 V vs. lithium at 0.05 mA/cm² shows this material to be an excellent candidate for the cathode of a low‐power, rechargeable lithium battery that is inexpensive, nontoxic, and environmentally benign. Electrochemical extraction was limited to ∼0.6 Li/formula unit; but even with this restriction the specific capacity is 100 to 110 mAh/g. Complete extraction of lithium was performed chemically; it gave a new phase, ${\mathrm{FePO}}_4$, isostructural with heterosite, ${\mathrm{Fe}}_{0.65}{\mathrm{Mn}}_{0.35}{PO}_4$. The ${\mathrm{FePO}}_4$ framework of the ordered olivine ${\mathrm{LiFePO}}_4$ is retained with minor displacive adjustments. Nevertheless the insertion/extraction reaction proceeds via a two‐phase process, and a reversible loss in capacity with increasing current density appears to be associated with a diffusion‐limited transfer of lithium across the two‐phase interface. Electrochemical extraction of lithium from isostructural ${\mathrm{LiMPO}}_4$ (M = Mn, Co, or Ni) with an ${\mathrm{LiClO}}_4$ electrolyte was not possible; but successful extraction of lithium from ${\mathrm{LiFe}}_{1-x}{\mathrm{Mn}}_x{PO}_4$ was accomplished with maximum oxidation of the ${\mathrm{Mn}}^{3+}/{\mathrm{Mn}}^{2+}$ occurring at x = 0.5. The ${\mathrm{Fe}}^{3+}/{\mathrm{Fe}}^{2+}$ couple was oxidized first at 3.5 V followed by oxidation of the ${\mathrm{Mn}}^{3+}/{\mathrm{Mn}}^{2+}$ couple at 4.1 V vs. lithium. The ${\mathrm{Fe}}^{3+}‐O‐{\mathrm{Mn}}^{2+}$ interactions appear to destabilize the ${\mathrm{Mn}}^{2+}$ level and stabilize the ${\mathrm{Fe}}^{3+}$ level so as to make the ${\mathrm{Mn}}^{3+}/{\mathrm{Mn}}^{2+}$ energy accessible.

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.

A general energy balance for battery systems has been developed. This equation is useful for estimating cell thermal characteristics. Reliable predictions of cell temperature and heat‐generation rate are required for the design and thermal management of battery systems. The temperature of a cell changes as a result of electrochemical reactions, phase changes, mixing effects, and joule heating. The equation developed incorporates these effects in a complete and general manner. Simplifications and special cases are discussed. The results of applying the energy balance to a mathematical model of the $\mathrm{LiAl}/\mathrm{FeS}$ cell discharged through two different reaction mechanisms are given as examples. The examples illustrate how the energy equation may be applied to a specific system to examine the relative contributions corresponding to the terms in the equation. The examples show that the processes involved in cell heat generation may be complex and that the application of a sufficiently general energy equation is advantageous.

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.

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.

The adoption of sodium metal anodes is limited due to their poor coulombic efficiency stemming from dendritic plating morphologies and incomplete solid electrolyte interface (SEI) formation. This study presents a sodium metal battery electrolyte formulation utilizing lithium hexafluorophosphate as an additive, which selectively decomposes at the sodium metal interface to form a highly uniform, compact, and inorganic-rich SEI layer. This improved passivation layer enables >99% columbic efficiency operation of zero-excess sodium metal anodes. The mechanism of action of this additive is further elucidated using advanced surface characterization techniques including X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM) to show that SEI layers formed on zero-excess sodium metal anodes in the presence of LiPF₆ are thinner and more uniform than those formed in electrolytes without additives. Further, electron energy loss spectroscopy (EELS) reveals that SEI layers formed in the presence of LiPF₆ are enriched in lithium fluoride, a known component of high-quality SEI films in lithium-based battery systems and a direct decomposition product of the LiPF₆ additive, further establishing the role of LiPF₆ as a sacrificial film-forming additive for the stabilization of Na metal anode interfaces.

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Sodium-sulfur (Na-S) batteries hold promise as high-energy-density batteries for long-duration energy storage due to their high open circuit voltage and Earth-abundant active materials. However, low utilization of the sulfur active material limits the achievable specific capacity, especially when a liquid polysulfide catholyte is utilized. High-surface-area carbon materials demonstrate promise to increase sulfur utilization in a Na-S battery. To make the carbon host material applicable for a flow battery application, a binder is required to bind the carbon materials together and to a porous substrate. Here, we utilize a composite carbon paper electrode coated by polymer,carbon nanofibers (CNFs) and carbon black (CB). By varying the mass ratios of CNF to CB, we found that a 70/20/10 mass ratio of CNF/CB/binder provided the highest capacity (260 mAh g⁻¹ compared to the baseline of 156 mAh g⁻¹) and stable battery performance over 100 cycles. Analysis of the composite electrode and full cells reveals that the amount of CB in the composite electrode influences binder distribution, cell resistance, and full cell performance.

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The increasing demand for sustainable and safe energy storage technologies has accelerated research into aqueous sodium-ion batteries (SIBs). This study investigates the electrochemical performance and degradation mechanisms of Na₂FeP₂O₇/C (NFP) as a cathode material in aqueous SIBs. We evaluate NFP/C using cyclic voltammetry, galvanostatic charge-discharge cycling, X-ray diffraction, SEM, and ICP-MS, in both half-cell and symmetrical full-cell configurations. NFP/C exhibits an initial capacity of up to 83 mAh g⁻¹ in aqueous half-cells due to continuous Fe release into the electrolyte and the formation of a surface layer that progressively impedes Na⁺ insertion. Symmetrical full-cells demonstrate improved stability, retaining approximately 50 mAh g⁻¹ over 100+ cycles with near-100% Coulombic efficiency. Structural analysis confirms that the bulk pyrophosphate framework is preserved during both chemical immersion and electrochemical cycling, although surface-level reactivity with the electrolyte is detected even at open circuit through the formation of a minor secondary crystalline phase. These findings suggest the potential of NFP/C for aqueous SIBs if strategies to suppress surface degradation can be developed.

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The implementation of silicon (Si) and silicon oxide (SiO_x) anodes for lithium-ion batteries (LIBs) is hindered by first-cycle capacity loss and low Coulombic efficiency due to unstable solid electrolyte interphase (SEI) formation, which consumes lithium and leads to poor cycle life. Here, we present an electrochemical continuous stirred tank reactor (ECSTR) as a platform for ex situ pre-lithiation of Si and SiO_x anode materials. Unlike conventional techniques, which suffer from poor lithium distribution and limited scalability, our ECSTR enables uniform, controlled lithiation of Si-based powders through stirring, optimized electrode configurations, and enhanced ion transport. The system, comprising a lithium ingot anode and copper foil cathode, facilitates lithium incorporation in a silicon/silica suspension in electrolyte. Electrochemical characterization, including cyclic voltammetry and impedance spectroscopy, confirms lithiation within 0 V to −2V, with controlled deposition. The process yields reproducible lithiated Si, demonstrating a linear correlation between lithiation capacity and processing time. ECSTR offers a scalable approach for lithiation of various materials, including transition metal oxides and alloy systems, with implications for next-generation non-lithium technologies. Future research integrating real-time monitoring and advanced electrolytes will enhance ECSTR, positioning it as a transformative tool for electrochemical processing across energy storage, catalysis, and material synthesis.

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SrTi_1-xFe_xO_3-δ (STF) is a promising mixed ionic–electronic conducting fuel-electrode materials for solid oxide cells (SOCs). However, STF is unstable under highly reducing operating conditions. Here, we investigate the effect of La substitution for Sr on phase stability and electrochemical performance of La_xSr_1-xTi_1-yFe_yO_3-δ (LSTF) using in situ X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS). In situ XRD reveals that STF forms a trace amount of n = 1 Ruddlesden–Popper (R–P) phase under $\frac{{P}_{{H}_{2}}}{{P}_{{H}_{2}O}}=4$ and extensively decomposes in more reducing conditions ($\frac{{P}_{{H}_{2}}}{{P}_{{H}_{2}O}}=5.67$). 10% La substitution significantly suppresses R–P formation, yielding full stability at $\frac{{P}_{{H}_{2}}}{{P}_{{H}_{2}O}}=4$ and significantly reduced decomposition in $\frac{{P}_{{H}_{2}}}{{P}_{{H}_{2}O}}=5.67$. Electrochemical testing shows that L₁₀STF exhibits slightly higher initial resistance than STF but demonstrates improved long-term stability due to its improved phase stability. These results highlight the critical role of A-site chemistry in governing perovskite stability and underscore the value of time-resolved in situ XRD for elucidating phase-transformation pathways in SOC operating conditions.

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Starting batteries are critical electrochemical energy storage systems that deliver high power pulses for engine ignition and auxiliary electrical functions. Their performance, durability, and safety are governed by complex electrochemical interactions involving electrode materials, electrolytes, interfacial processes, and operating conditions. This review provides a comprehensive electrochemical perspective on major starting battery technologies, including flooded lead–acid, absorbed glass mat, gel cell, lithium-ion, and nickel–cadmium batteries. Key electrochemical performance-limiting factors such as charge–discharge behavior, polarization losses, internal resistance, ion transport, and electrode–electrolyte interfacial stability are systematically analyzed. Further, the review emphasizes degradation and aging mechanisms such as sulfation, grid corrosion, gas evolution, lithium plating, and thermal runaway. It explains their electrochemical origins and how they affect long-term battery stability. The effects of temperature, charge rate, discharge rate, and material composition on electrochemical efficiency and cycle life are critically discussed. Recent advances in electrode materials, electrolyte systems (gel, polymer, ionic liquid, and deep eutectic electrolytes), and separator design are reviewed from an electrochemical perspective. These advances focus on strategies to enhance charge-transfer kinetics, suppress degradation, and improve thermal stability. Finally, key challenges and future research directions are outlined to guide the development of robust and sustainable next-generation starting batteries.

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Zirconium (Zr) possesses outstanding properties, including exceptional chemical resistance and a high melting point, and is therefore desirable for use in a wide variety of challenging environments, such as in nuclear reactors and the chemical processing industry. To minimize the amount of Zr required for any given application, developing methods for generating metallic Zr coatings is highly advantageous. Owing to Zr’s highly negative reduction potential, electrodeposition in traditional solvents at near ambient temperatures remains challenging and thus not well understood. Due to the extreme conditions required to deposit this metal, extensive work has been conducted in molten salt electrolytes, however the broad applicability of this methodology is limited due to its corrosivity. The primary focus of this article is to present an overview of Zr’s electrochemical behavior and to consolidate the efforts of researchers in exploring electrodeposition techniques for Zr involving aqueous, organic, ionic liquid, deep eutectic, and molten salt solvents. With this information, we highlight trends across solvent systems and opportunities for future research.

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This study presents a thorough analysis of machine learning techniques utilized for monitoring the health and predicting the remaining useful life (RUL) of lithium-ion batteries, which is essential for optimizing the performance of electric vehicles (EVs). Given the challenges faced by lithium-ion batteries, such as capacity fading and environmental factors, key indicators like State of Health (SOH) and RUL become vital. The paper reviews several adaptive machine learning methodologies, including Support Vector Regression (SVR), Gaussian Process Regression (GPR), and hybrid neural networks that integrate convolutional neural networks (CNNs) with long short-term memory (LSTM) algorithms. Special emphasis is placed on these models’ effectiveness in addressing the complex nonlinear behaviors associated with battery aging. Moreover, innovative approaches like fuzzy logic systems are examined, showcasing their potential to enhance SOH estimation via adaptable rule-based techniques. The manuscript stresses the necessity of integrating multiple methodologies to enhance predictive accuracy and reliability. By compiling empirical studies, the work aims to elucidate the capabilities of these algorithms, thereby enriching the knowledge base within battery management systems. Ultimately, this research aims to drive advancements in efficient energy storage solutions, which are crucial for the sustainable development of electric mobility.

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Highlights

• Machine learning techniques like CNN and DNN significantly enhance the prediction accuracy of battery health by modeling complex relationships.

• Gaussian Process Regression (GPR) effectively addresses battery aging issues by flexibly modeling nonlinear relationships and estimating prediction uncertainty.

• Condition monitoring utilizes critical parameters such as voltage and temperature to improve state-of-health and remaining useful life assessments.

• Machine learning algorithms are essential for predicting battery failure signs and diagnosing degradation trends, thereby enhancing energy storage system reliability.

• Various methodologies for estimating state-of-health showcase a mixture of experimental and adaptive techniques aimed at refining battery health evaluation.

This narrative summarizes, in retrospect, the enormous and quietly-conducted contribution of Dr Johan Coetzer, a South African scientist and entrepreneur, to the discovery, development and implementation of the high temperature sodium—metal chloride “ZEBRA” battery (Na/β-Al₂O₃, NaAlCl₄/MCl₂ (M = Ni, Fe)). This research activity was initiated in the mid 1970’s at the Council for Scientific and Industrial Research (CSIR) in South Africa and subsequently developed primarily in partnership with the Atomic Energy Research Establishment (AERE, Harwell, UK), Beta R&D (Derby, UK) and Daimler Benz (Germany), before being transferred to industry worldwide for electric vehicle and energy storage applications, albeit at a relatively low production rate. Coetzer’s wide-ranging, innovative and, at times, unconventional scientific approach also laid the foundation for the discovery and implementation of manganese-based spinel and layered metal oxide cathode materials for the Li-ion battery industry.

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Since the discovery of oxygen meters by Leland C. Clark (1956), the United States of America (USA) has been continually investigating efficient electrochemical sensors (E-Sens) to measure markers in line with demand and scope. The success of the glucometer (1962) accelerated the focus from developing selective, sensitive, and stable (SSS) sensing prototypes. Over time, in the USA, systematic multidisciplinary research is being conducted to overcome sensing challenges and achieve desired features, such as high sensitivity, high selectivity, longer stability, portability, personalized sensing, and validation to transform sensing prototypes for efficient management of targeted issues. Such sensing technology, supported by 4th (nano-enabled chips and sensing prototypes), 5th [Internet of Things (IoT)-based approaches, i.e., hardware and electronics], and 6th generation [Artificial Intelligence (AI)-based approaches, i.e., software] E-Sens technology, to transform them into acceptable, affordable, and applicable (AAA) commercial products with a market. Such optimized and transformative E-Sens perform testing in point-of-care (PoC) and point-of-use (PoU) settings to track a marker, perform risk assessments, and decision-making, needed to support the quality of life. To highlight these state-of-the-art E-Sens on the 250th independent anniversary of the USA, this comprehensive commentary article discusses the journey and standing of E-Sens, along with trends, challenges, and perspectives on personalized sensing.

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Highlight

• The USA is continually investigating efficient E-Sens for every field and everyone.

• Success of the glucometer (1962) accelerated the focus to develop next-generation E-Sens.

• 4th (nano-enabled chips), 5th (IoT-Hardware), and 6th (AI-Software) generation E-Sens technology are emerging for personalized Sensing.

• E-Sens’s journey and standing on the USA’s 250th anniversary are discussed in this article.

This study investigates aqueous electrolytes for efficient iron electrodeposition directly from Fe³⁺ at ambient temperature. Concentrated lithium chloride (LiCl) based electrolytes were found to stabilize the Fe³⁺ in the electrolyte, suppress parasitic hydrogen evolution and suppress redox shuttling of intermediate Fe²⁺, thus promoting efficient iron electrodeposition. These attributes collectively enabled high Coulombic efficiencies (>75%) at high current densities (>200 mA cm⁻²). Furthermore, detailed investigation revealed that increasing the LiCl concentration increased the electrolyte viscosity and decreased the Fe²⁺ out-diffusion rate while also suppressing the activity of water. Sufficiently high LiCl concentrations (>7 M) thus provide a window of current densities in which elevated Coulombic efficiencies can be achieved. Overall, this paper develops an understanding of the effects of electrolyte composition on the competition between Fe electrodeposition, hydrogen co-evolution, and intermediate Fe²⁺ out-diffusion for efficient Fe metal electrosynthesis.

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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.

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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.

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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.

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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.

Heavy metal contamination remains a critical global challenge with serious implications for environmental safety and public health. Electrochemical sensing techniques have emerged as powerful tools for detecting heavy metals due to their high sensitivity, portability, rapid response, and cost-effectiveness. Despite significant progress, translating laboratory-scale electrochemical sensors into reliable, field-deployable systems remains constrained by challenges such as poor selectivity in complex matrices, electrode fouling, reproducibility issues, and the need for extensive sample pretreatment. This review critically examines recent advances (post-2020) in electrochemical techniques for heavy metal detection, encompassing voltammetry, potentiometry, and electrochemical impedance spectroscopy. Particular emphasis is placed on the role of advanced electrode materials, including nanomaterials, nanocomposites, and biofunctional interfaces, in enhancing sensitivity, selectivity, and operational stability. Beyond material innovation, this review highlights emerging trends in microfluidics and sustainable electrode design, as well as the integration of Internet of Things (IoT) platforms and artificial intelligence-assisted data analysis for smart sensing. Practical limitations and performance trade-offs under real environmental conditions are systematically analysed. Finally, future directions are outlined, focusing on standardisation, sustainability, and the development of robust, user-friendly, and interconnected electrochemical sensors capable of real-time environmental monitoring and large-scale deployment.

Laser and electrochemical machining exhibits significant potential for high-efficiency, high-quality surface micromachining. However, its widespread application is hindered by constrained laser coupling efficiency and process instability, often stemming from uncontrollable laser intensity distribution and the requirement for external power sources. The present study proposed a method of lensed fiber-based chemical solution assisted laser processing (CALP). By utilizing a lensed fiber for laser transmission and focusing, the laser intensity in the machining zone is significantly localized and enhanced compared to conventional flat-ended fibers. Furthermore, the energy density can be precisely regulated by modulating the machining gap. Numerical and experimental results demonstrate that the lensed fiber-based head reduces the laser intensity spread width by 54.2% while increasing the peak intensity by 307.2%. Compared to flat-ended fiber processing, CALP with lensed fiber achieves an 84% increase in microgroove depth and a 32.3% reduction in width. Crucially, material removal is governed by the synergistic effects of direct laser ablation and self-induced thermo-electrochemical machining, with respective volume contributions of 25.87% and 71.43%. This lensed fiber-based CALP provides a robust and controllable paradigm for high-precision surface microfabrication on metallic materi

Atmospheric corrosion severity is typically assessed using base-metal witness coupons, which provide limited insight into mechanistic drivers for noble metals. In this work, we present a kinetic Monte Carlo (KMC) framework for simulating atmospheric corrosion of silver under thin-film electrolyte conditions. The model integrates coordination-number dependent oxidation and reduction kinetics with photon-mediated oxidant generation, oxygen reduction, chloride deposition, electrolyte transport, and AgCl precipitation. Simulations capture the coupled oxidation–precipitation dynamics that govern silver corrosion, including the transition from activation-controlled to transport-limited behavior associated with salt-film formation. The framework also naturally produces stochastic variability across replicate simulations, reflecting the sensitivity of corrosion pathways to local surface structure and environmental conditions. The results highlight threshold-driven corrosion behavior as a function of ultraviolet photon flux, chloride availability, temperature, and electrolyte conditions, and demonstrate how local interactions give rise to emergent corrosion morphologies. The KMC approach resolves mechanistic processes at the surface level and provides a physically based framework for interpreting trends and variability in atmospheric corrosion environments, complementing empirical classification methods such as ISO 9223.

With increasing deployment of high-capacity sodium-ion batteries (SIBs) in energy storage systems, overcharge-induced thermal runaway (TR) has become a critical safety concern. This study investigates the thermal-mechanical responses of 50 Ah, 185 Ah, and 210 Ah SIBs under low- and high-current overcharge conditions. Results show that increasing capacity markedly intensifies TR hazards. Under low-current overcharge, peak temperature increased from 394.2 °C to 688.5 °C as capacity increased from 50 Ah to 210 Ah, while the maximum expansion force reached 11836.4 N. Pre-TR heat accumulation was dominated by side reaction heat, accounting for 69.8%–82.1% under low current. High-current overcharge enhanced Joule heating, raising peak temperatures of the 185 Ah and 210 Ah SIBs to 729.0 °C and 792.4 °C, respectively, but shortened reaction duration and reduced maximum expansion force to 6849.9 N and 9547.5 N. The side reaction heat proportion consequently decreased to about 60%. A three-level early-warning strategy integrating force, temperature, and voltage signals was established, achieving a maximum lead time of 991 s. This work provides guidance for TR risk assessment and safety design of high-capacity SIB systems.

Polymer electrolyte water electrolysis (PEWE) is a promising route for sustainable hydrogen production, but its deployment is constrained by the cost and scarcity of iridium-based oxygen evolution reaction (OER) catalysts. Reducing the anode Ir loading while maintaining performance requires careful optimization of the catalyst layer (CL) architecture. In this work, commercial TiO2-supported iridium oxide (IrOx) catalysts with Ir contents ranging from 10 to 75 wt.% were systematically evaluated at fixed Ir loadings of 0.5 and 0.1 mgIr cm-2. By combining structural characterization, intrinsic electronic conductivity measurements, and electrochemical analysis, correlations between catalyst composition, CL thickness, and electrolysis performance were established. The catalysts with low Ir contents (10 wt.%) formed thick, TiO2-rich layers associated with limited electronic connectivity, whereas those with high-Ir contents (75 wt.%) produced ultrathin layers that, despite improved electronic conductivity, showed reduced effective catalyst utilization and increased sensitivity to structural inhomogeneity. These findings demonstrate that efficient low-Ir anodes require joint optimization of Ir content, catalyst layer thickness, and microstructural connectivity to balance conductive network formation and effective transport pathways. Intermediate-Ir catalysts (30–45 wt.%) represent the most practical pathway toward scalable, low-Ir PEMWE electrodes.

Sodium-sulfur (Na-S) batteries hold promise as high-energy-density batteries for long-duration energy storage due to their high open circuit voltage and Earth-abundant active materials. However, low utilization of the sulfur active material limits the achievable specific capacity, especially when a liquid polysulfide catholyte is utilized. High-surface-area carbon materials demonstrate promise to increase sulfur utilization in a Na-S battery. To make the carbon host material applicable for a flow battery application, a binder is required to bind the carbon materials together and to a porous substrate. Here, we utilize a composite carbon paper electrode coated by polymer,carbon nanofibers (CNFs) and carbon black (CB). By varying the mass ratios of CNF to CB, we found that a 70/20/10 mass ratio of CNF/CB/binder provided the highest capacity (260 mAh g⁻¹ compared to the baseline of 156 mAh g⁻¹) and stable battery performance over 100 cycles. Analysis of the composite electrode and full cells reveals that the amount of CB in the composite electrode influences binder distribution, cell resistance, and full cell performance.

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The increasing demand for sustainable and safe energy storage technologies has accelerated research into aqueous sodium-ion batteries (SIBs). This study investigates the electrochemical performance and degradation mechanisms of Na₂FeP₂O₇/C (NFP) as a cathode material in aqueous SIBs. We evaluate NFP/C using cyclic voltammetry, galvanostatic charge-discharge cycling, X-ray diffraction, SEM, and ICP-MS, in both half-cell and symmetrical full-cell configurations. NFP/C exhibits an initial capacity of up to 83 mAh g⁻¹ in aqueous half-cells due to continuous Fe release into the electrolyte and the formation of a surface layer that progressively impedes Na⁺ insertion. Symmetrical full-cells demonstrate improved stability, retaining approximately 50 mAh g⁻¹ over 100+ cycles with near-100% Coulombic efficiency. Structural analysis confirms that the bulk pyrophosphate framework is preserved during both chemical immersion and electrochemical cycling, although surface-level reactivity with the electrolyte is detected even at open circuit through the formation of a minor secondary crystalline phase. These findings suggest the potential of NFP/C for aqueous SIBs if strategies to suppress surface degradation can be developed.

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SrTi_1-xFe_xO_3-δ (STF) is a promising mixed ionic–electronic conducting fuel-electrode materials for solid oxide cells (SOCs). However, STF is unstable under highly reducing operating conditions. Here, we investigate the effect of La substitution for Sr on phase stability and electrochemical performance of La_xSr_1-xTi_1-yFe_yO_3-δ (LSTF) using in situ X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS). In situ XRD reveals that STF forms a trace amount of n = 1 Ruddlesden–Popper (R–P) phase under $\frac{{P}_{{H}_{2}}}{{P}_{{H}_{2}O}}=4$ and extensively decomposes in more reducing conditions ($\frac{{P}_{{H}_{2}}}{{P}_{{H}_{2}O}}=5.67$). 10% La substitution significantly suppresses R–P formation, yielding full stability at $\frac{{P}_{{H}_{2}}}{{P}_{{H}_{2}O}}=4$ and significantly reduced decomposition in $\frac{{P}_{{H}_{2}}}{{P}_{{H}_{2}O}}=5.67$. Electrochemical testing shows that L₁₀STF exhibits slightly higher initial resistance than STF but demonstrates improved long-term stability due to its improved phase stability. These results highlight the critical role of A-site chemistry in governing perovskite stability and underscore the value of time-resolved in situ XRD for elucidating phase-transformation pathways in SOC operating conditions.

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Atmospheric corrosion severity is typically assessed using base-metal witness coupons, which provide limited insight into mechanistic drivers for noble metals. In this work, we present a kinetic Monte Carlo (KMC) framework for simulating atmospheric corrosion of silver under thin-film electrolyte conditions. The model integrates coordination-number dependent oxidation and reduction kinetics with photon-mediated oxidant generation, oxygen reduction, chloride deposition, electrolyte transport, and AgCl precipitation. Simulations capture the coupled oxidation–precipitation dynamics that govern silver corrosion, including the transition from activation-controlled to transport-limited behavior associated with salt-film formation. The framework also naturally produces stochastic variability across replicate simulations, reflecting the sensitivity of corrosion pathways to local surface structure and environmental conditions. The results highlight threshold-driven corrosion behavior as a function of ultraviolet photon flux, chloride availability, temperature, and electrolyte conditions, and demonstrate how local interactions give rise to emergent corrosion morphologies. The KMC approach resolves mechanistic processes at the surface level and provides a physically based framework for interpreting trends and variability in atmospheric corrosion environments, complementing empirical classification methods such as ISO 9223.

Gas Diffusion Electrodes (GDE) are porous structures, where a liquid electrolyte is brought into contact with a gas phase in the presence of a conducting electrocatalyst. To hinder the electrolyte from breakthrough, hydrophobic components, i.e. PTFE, are added to the electrode structure. In pores with stagnant free electrolyte surface, the gaseous species dissolves into the electrolyte and the electrochemical reaction takes place at the surface of the wetted electro catalyst. To predict the GDE performance from first principles we propose to rigorously simulate the electrolyte distribution in pores with stagnant free surfaces. Using an independently determined rate expression for the electrochemical reaction allows calculating the integral reaction rate of a single pore. To simplify calculations we demonstrate that it is sufficient to use a correlation for the oxygen consumption derived from an equivalent elliptic pore. Knowledge of free surface area and contact line length uniquely determines the elliptical pore. The oxygen reduction reaction on a silver/PTFE GDE serves as an example. In the future the integral reaction rate of a single pore will be incorporated in a pore network model to predict GDE performance from fully resolved pore geometry and an independently determined reaction kinetics.

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An impurity phase, Na₃MnO₄, is often overlooked during the synthesis of Mn-based sodium layered oxides due to its absence in X-ray diffraction (XRD) patterns, leading to misjudged phase purity and overestimated Na/TM ratios in the targeted materials. In this work, we confirmed its presence through titration and elemental analysis and showed its profound influence on the electrochemical responses. We proposed that Na₃MnO₄, formed at elevated temperatures, rapidly degrades in ambient air because of its highly hygroscopic nature and reactivity with water, rendering it “invisible” to XRD. Remarkably, incorporating 2 at.% Ca not only improves the air stability of the host materials but also stabilizes the Na₃MnO₄ impurity phase, making it detectable by XRD. This simple yet effective strategy is applicable to various Mn-based sodium layered oxides and offers new insights into their phase purity and accurate Na/TM ratio.

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Polymer electrolyte water electrolysis (PEWE) is a promising route for sustainable hydrogen production, but its deployment is constrained by the cost and scarcity of iridium-based oxygen evolution reaction (OER) catalysts. Reducing the anode Ir loading while maintaining performance requires careful optimization of the catalyst layer (CL) architecture. In this work, commercial TiO2-supported iridium oxide (IrOx) catalysts with Ir contents ranging from 10 to 75 wt.% were systematically evaluated at fixed Ir loadings of 0.5 and 0.1 mgIr cm-2. By combining structural characterization, intrinsic electronic conductivity measurements, and electrochemical analysis, correlations between catalyst composition, CL thickness, and electrolysis performance were established. The catalysts with low Ir contents (10 wt.%) formed thick, TiO2-rich layers associated with limited electronic connectivity, whereas those with high-Ir contents (75 wt.%) produced ultrathin layers that, despite improved electronic conductivity, showed reduced effective catalyst utilization and increased sensitivity to structural inhomogeneity. These findings demonstrate that efficient low-Ir anodes require joint optimization of Ir content, catalyst layer thickness, and microstructural connectivity to balance conductive network formation and effective transport pathways. Intermediate-Ir catalysts (30–45 wt.%) represent the most practical pathway toward scalable, low-Ir PEMWE electrodes.

Composite materials containing heterointerfaces composed of two or more metal oxides are functional materials with great potential for a wide range of applications in various fields. If methods for controlling the nanoscale structure of such metal oxide heterointerfaces can be established, it is expected to not only improve properties through an increased specific surface area but also enable the incorporation of new functions based on geometric structures. In this study, we fabricated ordered metal oxide nanohole arrays with heterointerfaces formed by anodization. To verify the fabrication process, we prepared a nanohole array with a heterointerface composed of Nb2O5 and WO3. By mask-assisted sputtering, we formed a composite thin film composed of Nb and W on the surface of the template. The template was then removed to obtain a composite thin film with a regular dimple pattern on its surface. The anodization of the obtained sample resulted in pore growth originating from the dimples in both the Nb and W regions, enabling the formation of an ordered nanohole array with metal oxide heterointerfaces. This process is expected to enable the fabrication of ordered nanohole arrays with a heterointerface composed of various metal oxides.

This paper presents a new physics-based 0D steady-state model for simulating the performance of proton-exchange membrane fuel cells (PEMFC), including phenomena such as temperature gradients, transport of membrane water, liquid water and gases. The model adopts an explicit formulation resulting in extremely low computational times, enabling sensitivity analyses, parameter estimation and cross-validation, to an extent which has not been previously reported for PEMFC models. Validation against polarization curves, high-frequency resistance, crossover current density, and roughness factor measurements for fifteen operating conditions demonstrates very good predictive accuracy. With 18 estimated parameters, the model achieves median root-mean square errors of 14.1 mV and 3.6 mΩ cm² for cell voltage and high-frequency resistances on testing datasets. However, overfitting becomes evident when the number of estimated parameters is increased. Beyond performance prediction, this work underscores the importance of robust parameter estimation and cross-validation in PEMFC modelling. It also highlights the potential of lightweight 0D physics-based models for accurate performance prediction and interpretation of experimental data.

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This work introduces a unified interpretability-efficiency framework for lithium-ion battery state of health (SOH) prediction using hybrid deep learning architectures. We comparatively analyze four hybrid models: CNN LSTM MultiHead, CNN Feature Extractor LSTM, DNN LSTM, and DNN BiLSTM to disentangle how network topology, feature composition, and computational design influence both predictive fidelity and physical interpretability. By integrating Monte Carlo Shapley (MC Shapley), background occlusion SHAP (BoSHAP), and ablation analysis, we quantify the contribution and robustness of five electrochemical feature groups: time, capacity, voltage, dQ/dV and peaks of dQ/dV from NASA battery dataset. The results reveal a consistent dominance of differential capacity (dQ/dV) and capacity features, aligning with their electrochemical significance in phase transition dynamics and active material loss, while voltage and capacity provide stabilizing redundancy. The ablation derived Area Under the Ablation Curve (AUAC) establishes a precision-robustness tradeoff, and efficiency analyses expose an accuracy-latency Pareto frontier where DNN LSTM achieves sub 1% RMSE with compact parameterization, while CNN FE LSTM attains sub 10 ms inference suitable for embedded BMS deployment.

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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.

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.

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 kinetics of the hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) on polycrystalline platinum [Pt(pc)] and high surface area carbon-supported platinum nanoparticles (Pt/C) were studied in 0.1 M KOH using rotating disk electrode (RDE) measurements. After corrections of noncompensated solution resistance from ac impedance spectroscopy and of hydrogen mass transport in the HOR branch, the kinetic current densities were fitted to the Butler–Volmer equation using a transfer coefficient of $\alpha =0.5$, from which HOR/HER exchange current densities on Pt(pc) and Pt/C were obtained, and the HOR/HER mechanisms in alkaline solution were discussed. Unlike the HOR/HER rates on Pt electrodes in alkaline solution, the HOR/HER rates on a Pt electrode in 0.1 M ${\text{HClO}}_4$ were limited entirely by hydrogen diffusion, which renders the quantification of the HOR/HER kinetics impossible by conventional RDE measurements. The simulation of the hydrogen anode performance based on the specific exchange current densities of the HOR/HER at $80°C$ illustrates that in addition to the oxygen reduction reaction cell voltage loss on the cathode, the slow HOR kinetics are projected to cause significant anode potential losses in alkaline fuel cells for low platinum loadings ($130\text{mV}$ at $0.05{\text{mg}}_{\text{Pt}}/{\text{cm}}_{\text{anode}}^2$ and $1.5A/{\text{cm}}_{\text{anode}}^2$), contrary to what is reported for proton exchange membrane fuel cells.

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.