Journal of The Electrochemical Society

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.

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.

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.

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.

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.

Reversible extraction of lithium from (triphylite) and insertion of lithium into 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, , isostructural with heterosite, . The framework of the ordered olivine 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 (M = Mn, Co, or Ni) with an electrolyte was not possible; but successful extraction of lithium from was accomplished with maximum oxidation of the occurring at x = 0.5. The couple was oxidized first at 3.5 V followed by oxidation of the couple at 4.1 V vs. lithium. The interactions appear to destabilize the level and stabilize the level so as to make the energy accessible.

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.

This study investigates the calendar ageing behaviour of NMC811//SiO_x-graphite 21700 cylindrical cells (LGM 50), which were held at varying states of charge (SoC), for up to 70 weeks at 4 different temperatures. Throughout the ageing study, capacity and internal resistance were monitored, and significant capacity loss over time, with greater loss at high SoC and temperature, were observed. A combination of electrochemical testing and post-mortem characterisation techniques point to the anode, more specifically, the silicon-oxide particles, as the driver of capacity fade through unstable solid-electrolyte interface dynamics, leading to the gradual loss of lithium inventory. Despite the greatest capacity loss being at ∼80% SoC and the apparent improvement in capacity retention at higher SoCs, i.e. the “spoon-shape effect,” the degradation is most pronounced at 100% SoC, driven by the instability of the silicon-oxide SEI. This is demonstrated by post-calendar ageing cycling of the cells, where those aged at 100% SoC degraded at a faster rate than 80% SoC.

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Highlights

• Higher temperatures and SoC levels significantly accelerate calendar ageing degradation of NMC//SiO_x-graphite cylindrical cells.

• Cells aged at 80% SoC showed larger capacity fade then cells stored at 100% SoC - this increase in capacity was found to be as a result of lithium inventory release due to more degradation.

• Despite the increase in capacity, more significant degradation was observed in cells aged at 100% SoC through advanced characterisation and cycling tests.

• Post-mortem analysis—including CT scanning, neutron and X-ray diffraction, SIMS/EDS, and differential voltage analysis—revealed that capacity fade is primarily attributed to the loss of active material in the anode and lithium inventory, especially associated with the presence of silicon.

Metallic lithium deposition (LD) is the key limiting factor for fast-charging of lithium-ion batteries, as it affects both safety and durability. The reliable detection of LD requires simple and rapid diagnostics, which has led to a widespread adaption of impedance-based LD detection methods in the literature. Most of these studies are largely phenomenological, offering limited insight into the underlying physicochemical mechanisms reflected in the impedance response. In contrast, this study takes an experimental approach by placing the cell under conditions where lithium deposition occurs as the main reaction. Thereby, a targeted analysis of its impact on impedance is enabled by slowly and homogeneously overcharging a graphite anode, which is combined with an oversized cathode in a three-electrode configuration. The setup allows to create controlled conditions from intercalation via the onset of LD to exclusively LD. The electrodes are analyzed using operando and ex-operando impedance measurements. Additionally, a distribution of relaxation times analysis is performed to gain deeper insight into the electrochemical processes under different LD conditions. This work thus bridges the gap between phenomenological detection methods and the fundamental understanding of LD, offering potential for an improved detection and prevention of LD and ultimately fast-charging of lithium-ion batteries.

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Highlights

• Conditions from intercalation via onset to mainly metallic lithium deposition created and systematically examined.

• Processes allocation by EIS & DRT.

• Recognition of fingerprints of metallic lithium deposition in SEI migration and charge-transfer processes.

• Validation and process assignment of operando-impedance results during lithium deposition.

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.

Co-free and Li-rich nickel manganese layered oxides (LR-NMs) are considered next-generation cathode active materials for Li-ion batteries, owing to their high energy density at low cost. However, this materials class suffers from an open-circuit-voltage (OCV) hysteresis, resulting in low energy efficiency. In this study, LR-NMs with varying Li and Mn contents (Li_1+δ[Ni_xMn_y]_1-δO₂ with x/y = 0.65/0.35, 0.50/0.50, 0.35/0.65 (x + y = 1), and δ = 0.10–0.20) are prepared and characterized by X-ray diffraction. Their composition-dependent OCV hysteresis is determined by charge/discharge tests with intermittent OCV periods. We demonstrate that increasing Li and/or Mn content increases the contribution of the reversible anionic redox at similar discharge capacities, concomitant with an increased OCV hysteresis between charge and discharge in the cycles following the first-cycle activation. This is supported by a linear increase of the OCV hysteresis with the anionic redox contribution for the LR-NM materials synthesized and examined in this study (seven different compositions, each prepared at three different calcination temperatures). Considering that the increase of the OCV hysteresis with increasing overlithiation δ and/or Mn content y results in an intrinsically inferior energy efficiency, possible strategies for future LR-NM materials development are discussed.

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High chloride concentrations in industrial brines, such as those encountered in lithium extraction, critically challenge the localized corrosion resistance of structural alloys. This study investigates the effect of chloride concentration on the corrosion behavior of Zeron® 100 super duplex stainless steel (UNS S32760) by evaluating critical pitting temperature (CPT), critical crevice temperature (CCT), pitting potential (E_pit), and crevice repassivation potential (E_rep) across a wide range of chloride concentrations (1–8 M). CPT, CCT, and E_rep decreased logarithmically with chloride concentration, indicating a progressive reduction in localized corrosion resistance. At the highest Cl⁻ concentrations, E_rep falls below the corrosion potential, implying that spontaneous crevice corrosion is thermodynamically feasible under open-circuit conditions. SEM analysis reveals that increasing chloride concentration alters pit morphology and reduces the protective nature of the lacy cover. These findings provide new insights into the degradation mechanisms of Zeron® 100 in chloride-rich environments and highlight the importance of considering E_rep, in addition to CPT and E_pit, when predicting long-term performance.

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Highlights

• Systematic degradation of localized corrosion resistance was observed for Zeron® 100 (UNS S32760) SDSS with increasing chloride concentration, indicated by a logarithmic decrease in CPT, CCT, and E_rep.

• Repassivation potential decreased to values below the corrosion potential at high chloride concentrations, suggesting spontaneous crevice corrosion under open-circuit conditions.

• Pit and crevice morphologies evolved with Cl⁻ concentration, showing more porous lacy covers and deeper undercutting at higher Cl⁻ levels.

• Zeron 100’s performance limitations in extreme Cl⁻ environments highlight the importance of E_rep as a conservative and reliable parameter for long-term corrosion prediction in hydrometallurgical applications.

The electrochemical CO₂ reduction (CO₂RR) holds promise for sustainable fuel and chemical production, but faces challenges in maintaining catalyst stability under industrial conditions, particularly at elevated temperatures. This study investigates CO₂RR performance at 85 °C using three types of carbon-based bismuth catalyst in a flow-by electrolyzer. Elevated temperatures accelerate degradation processes, making long-term operation difficult. We synthesized and tested catalysts where carbon serves as a structural support to disperse and stabilize Bi-based particles. While commercial bismuth oxide nanoparticles initially exhibit high selectivity toward formate (85%), their faradaic efficiency (FE) declined by 20% over 24 h. In contrast, Bi@C, where carbon acts as a porous support material to anchor nanoparticles and enhance dispersion, showed greater structural resilience, maintaining 75% initial selectivity with only a 10% drop over the same period. Post-electrolysis scanning electron microscopy (SEM) and high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) further confirmed that Bi@C underwent only minor morphological changes compared to its carbon-free counterpart, thereby explaining its enhanced stability. These findings provide insights into the role of carbon in stabilizing electrocatalysts at elevated temperatures, underscoring the required advancements to enable long-term CO₂ electrolysis under industrially relevant conditions of temperature and current density.

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This study investigates the performance and structural stability of commercial micron-sized tin (Sn) particles as anode active material for sodium-ion batteries. Despite undergoing significant volume change during cycling, the Sn anode demonstrates stable capacity retention over 450 cycles in Sn/Na half-cells with an ether-based electrolyte. Initially fragmented Sn particles restructure into uniformly dispersed 1-micron sized spheres within the first 50 cycles. The restructuring process is hypothesized to result from the interplay between fragmentation and particle coalescence, preventing further pulverization. In the case of incomplete (de)sodiation, the voltage profile gradually evolves over cycling which suggests the development of an inhomogeneous morphology within the Sn electrode. To assess Na inventory loss during restructuring, a limited-inventory protocol was developed for Sn/Na cells, resulting in 95% of capacity retention over 100 cycles. Full NFPP/Sn coin cells only show 84% capacity retention after 100 cycles, which suggests additional parasitic reactions. An in situ pressure measurement was performed on a multi-layer NFPP/Sn pouch cell to monitor the stack pressure change. These results highlight the potential of Sn anodes and emphasize the need to address issues related to parasitic reactions and electrode volume expansion for their successful integration into practical sodium-ion batteries.

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Amorphous metal oxide surfaces play a key role in electrocatalysis. Yet at present we know very little about the atomic structure of these amorphous metal oxide surfaces and the precise phenomena occurring at the liquid solid interface of these materials. Here we show that under oxidative conditions Au³⁺ cations are constantly being formed within amorphous gold oxide, and that these are the main cause for previously not understood phenomena such as potential shifts of the oxide reduction peaks. The Au³⁺ cations play a crucial role in the chemistry of gold oxide, where these form bonds with nucleophiles present within the amorphous gold oxide layer and the electrolyte solution, thereby dominating the interactions at the solid-liquid interface. Moreover we show that these exposed cationic sites play a crucial role not only in the structure of the solid-liquid interface but also actively take part in the catalytic water oxidation reaction.

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Highlights

• First clear evidence that Au³⁺ causes abnormal shifts in oxide reduction peaks

• Revealing how Au³⁺ enables the formation of disordered amorphous oxide structures

• Au³⁺ found to play a key role in stabilizing the oxide–solution interface

• pH-dependent OER activity explained by bonding changes of Au³⁺ on oxides

Against the backdrop of swiftly evolving flexible electronics and wearable device technologies, polymer electrolytes are increasingly recognized as pivotal materials for safe and high-performance solid-state battery systems. This review systematically summarizes the recent progress in solvent-free polymer electrolytes, gel polymer electrolytes, and composite polymer electrolytes, focusing on their ion conduction mechanisms, performance optimization strategies, and applications in flexible energy storage systems. The unique advantages of polymer electrolytes, such as high safety, flexibility, and processability, are highlighted, along with critical challenges in ionic conductivity, mechanical strength, and interface compatibility. Emerging applications in supercapacitors, wearable electronics, and medical devices are discussed, emphasizing the importance of multi-scale structural design and interdisciplinary innovation. Future perspectives include the integration of dynamic bionic design, in situ characterization, 3D printing, and artificial intelligence-driven material screening to address current bottlenecks, paving the way for next-generation flexible energy storage technologies.

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Silver nanoparticles have garnered significant attention due to their unique properties, including high surface area, excellent electrical conductivity, and catalytic activity. The present review explores the synthesis methods, characterization, properties, and applications of AgNPs, particularly in the field of energy storage. Multiple synthesis techniques including physical, chemical, and biological methods are discussed and their advantages and limitations are emphasized. The properties of AgNPs, such as size-dependent optical behavior, enhanced surface reactivity, and stability play a pivotal role in their integration into energy storage devices. Specifically, AgNPs have shown promise in improving the performance of supercapacitors, lithium-ion batteries and other energy storage systems by enhancing charge or discharge rates, cycling stability, and overall efficiency. Additionally, the potential for AgNPs in hybrid energy storage systems and their ability to optimize the performance of electrodes is explored. This review also addresses the challenges associated with the scale-up of AgNP production, environmental concerns, and the future prospects for AgNPs in energy storage technologies. The growing interest in these nanoparticles underscores their potential to contribute to the development of next-generation energy storage solutions.

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Mycotoxins are toxic compounds with significant risks to human and animal health due to its presence in contaminated food and feed. The conventional methods for detecting mycotoxins include chromatographic techniques which are sensitive but often costly and time-consuming. Alternative methosds involve the use of electrochemical sensors which have demonstrated promising results. This review explores the innovative use of metal−organic frameworks (MOFs) as platforms for electrochemical sensors in mycotoxin detection. Integrating MOFs into electrochemical devices has led to the development of various sensor types, including MOF composites and MOF−based biosensors, which demonstrate high stability, low detection limits, and applicability across different food samples. Key findings indicate that MOF−based sensors can achieve dection limits in the femtogram range and recoveries rates around 100% in real samples such as milk, juices or cereas. Moreover, these systems show excellent selectivity, even in the presence of interfering compouns. In this work, we addressed recent advancements in MOF−modified electrochemical sensors, detailing their key role, functionality, and practical applications in detecting important mycotoxins such as aflatoxins, deoxynivalenol, and ochratoxin, among others. It concludes with an evaluation of the challenges and prospects in the field, emphasizing the potential of MOFs to revolutionize mycotoxin detection and ensure food safety.

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Highlights

• Development of MOF-Based Electrochemical Sensors: The study presents innovative electrochemical sensors based on Metal-Organic Frameworks (MOFs) for detecting Aflatoxin B1 (AFB1) with high sensitivity and selectivity.

• Low Detection Limits: The proposed sensors demonstrate exceptionally low limits of detection (LOD), reaching the picomolar range, providing a significant advantage in early and rapid detection of hazardous substances in food samples.

• Enhanced Sensor Performance with MOF Composites: The use of MOF composites, particularly those based on 3 d metal ions, enhances the electro-reduction of ketone groups in aflatoxins and facilitates the immobilization of specific aptamers or antibodies, improving sensor performance.

• Selective Binding and Signal Amplification: By integrating aptamers and utilizing electrocatalysts like porphyrine Ti(II)-MOF doped with Pt+ ions, the sensors achieve selective binding of AFB1 and significant signal amplification, as demonstrated by electrochemical impedance spectroscopy (EIS) studies.

• Successful Application in Real Samples: The sensors have been successfully tested in real food samples, achieving high recovery rates and demonstrating their practical utility in routine food safety monitoring and quality control.

The success in reversible electrochemical intercalation of lithium cation into graphite electrode has boosted the development of lithium-ion batteries (LIBs) in the world. Nevertheless, there are many enigmas behind lithium storage behavior of graphite electrodes. During the study of the working mechanisms of graphite negative electrodes in LIBs, highly oriented pyrolytic graphite (HOPG) has led researchers to many important insights unambiguously through different electrochemical and in situ measurements. This review addresses how the special structural features of HOPG help recognize the electrochemical performance of graphite electrodes under different lithiation environments. Tracing the route of HOPG’s application in LIBs may be vital for understanding the exploration history of LIBs.

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Infectious diseases, triggered by pathogens such as bacteria, viruses, or parasites, propagate through contact, vectors, or environmental sources, often intensifying pandemics and causing significant societal disruptions. These diseases can severely impact global economies, employment, mental well-being, and public health. The rapid mutation of pathogens like SARS-CoV-2 complicates detection and treatment, making timely intervention crucial. Electrochemical biosensors, developed with advanced nanostructured biorecognition units and electroanalytical techniques, are central to addressing the challenges posed by SARS-CoV-2. The state-of-the-art research on electrochemical biosensors for SARS-CoV-2 diagnosis is thoroughly summarized in this review. These consist of the identification of spike protein (S protein)/RBD, nucleocapsid protein (N protein), antibodies, nucleic acids (RNA and DNA), entire viruses, and some of the biomarkers. Point-of-care (POC) devices have become essential in the fight against the pandemic, enabling rapid diagnosis, early treatment, and effective containment. They increase testing accessibility, reduce viral transmission, and ultimately save lives. This review highlights the latest advancements in electrochemical biosensors. It offers an overview of currently available POC devices/diagnostic tools (a total of 55 assay kits and devices) and the challenges of translating laboratory research into practical, deployable technologies. Additionally, the integration of artificial intelligence (AI), and machine learning (ML) with sensor data fusion (SDF) methods could be implemented for real-time analysis. The insights and innovations presented here aim to aid researchers in designing electrochemical sensors adaptable to future pathogens, advancing global health security.

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.

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 $\varphi$ change in a complementary manner. Changes in ${\mu }_{e}$ and $\varphi$ 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 ${\rm{\Delta }}{\mu }_{e}.$ The exchange current density ${j}_{0}$ appears as an exponential function of ${\rm{\Delta }}{\mu }_{e}.$ For the work function ${\rm{\Phi }}$ of the metal, the approximation ${\rm{\Delta }}{\mu }_{e}\approx -F{\rm{\Delta }}{\rm{\Phi }}$ yields a linear relationship between $\mathrm{ln}{j}_{0}$ and ${\rm{\Phi }}.$ The linear increase in $\mathrm{ln}{j}_{0}$ with ${\rm{\Phi }}$ 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.

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

Operando optical methods are widely used for measuring the properties of battery electrodes under charge/discharge conditions and provide valuable insights into various phenomena. However, the need to gain optical access to the electrode of interest often requires a compromise, such that the electrochemical characteristics of the operando cell deviate from those in a conventional cell. One approach towards minimally invasive optical spectroscopy is the “through-hole” coin cell configuration in which the bottom electrode is optically accessed via a hole punched through the top electrode and separator, but the impact of this hole on the validity of the measurement has been given little consideration. Here we performed modelling of graphite and lithium nickel manganese cobalt oxide (LiNi0.6Mn0.2Co0.2O2; NMC622) electrodes in a Li-ion half-cell arrangement, to explore this through-hole configuration. We show that the presence of a 0.5 mm radius hole results in a non-uniform Li+ ion distribution in the electrode phase, but this can be reduced by decreasing the current, decreasing the hole size or increasing the separator thickness. The Li+ non-uniformity varies non-linearly with the average degree of electrode lithiation and is more extreme for a graphite electrode compared to NMC622 due to their contrasting voltage-charge profiles.

The foundation of all electrochemical and supercapacitive energy storage systems is the current collector base, which is employed for deposition of active materials. This study aims to investigate the compatibility of a novel triazolium based dicationic salt as electrolyte for activated carbon (AC) electrodes on stainless steel and nickel foam current collectors. The dicationic salt exhibits a thermal stability of 270°C and potential window of 3 V, which is nearly the maximum stability for low concentration that has been reported. The activated carbon yielded a surface area of 695 m2/g. To assess the electrolytic performance of dicationic salt in device, cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy methods were used. For the AC-NF and AC-SS electrodes, the GCD cycles yielded specific energy and power of 0.416 W h/kg and 107.81 W/kg, respectively, and 1.842 W h/kg and 309.86 W/kg. AC-NF system retained 86% of capacitance after 3000 charging-discharging cycles with a current density of 0.21 A/g at 1 V, whereas the AC-SS system was able to maintain 81% of its initial capacitance after 3000 cycles with a current density of 0.33 A/g at 2 V. The findings suggest that AC-SS electrodes are more compatible with dicationic salt.

Studies have shown that using polydisperse active material particles can cause (i) heterogeneous electrochemical reactions within a battery electrode due to reactivity differences among different particle sizes, and (ii) heterogeneous electrode microstructures, leading to varied transport and charge transfer overpotentials throughout the electrode, exacerbating the reaction heterogeneity. The uneven utilisation of the battery electrode subjects certain electrode regions to greater electrochemical stress, with the risk of accelerated degradation. In this work, we focus on the impact of particle size distribution on battery electrode cyclability. First, we synthesised monodisperse polycrystalline LiNi1/3Mn1/3Co1/3O2 (NMC111) particles of two different sizes. Then, three electrodes with different particle size distributions (‘Small’, ‘Big’, ‘Mix’) were fabricated and examined as model systems. Contrary to our hypothesis that the ‘Mix’ electrode would exhibit the worst cyclability, the ‘Small’ electrode showed the best long-term cycling performance, followed by the ‘Mix’ electrode and then the ‘Big’ electrode. The discrepancy is attributed to the greater degree of particle cracking experienced by the big particles, disrupting solid-state charge transport within secondary particles, especially in the ‘Big’ electrode. Overall, this study provides new insights into synthesising monodisperse layered oxide cathodes and how both the average particle diameter and particle size distribution affect battery performance.

As of now, two-dimensional (2D) materials have gained huge attention for energy storage applications due to their unique structural and electrochemical properties. More than 1000 articles have been published focusing on various phases and heterostructures of 2D materials with experimental and computational investigations in energy related applications. Exploration of two-dimensional materials in ion batteries is growing rapidly, as their layered structure and surface chemistry provide new avenues for enhancing charge storage and transport. This review provides a systematic analysis of emerging 2D materials-including graphene, transition metal dichalcogenides, phosphorene, borophene, and MXenes-along with their heterostructures, examining their unique properties and technological potential, outlining their key benefits and drawbacks for use in ion batteries. In addition, we have also reviewed essential fundamental mechanisms governing ion diffusion, intercalation, and storage within two-dimensional materials, elucidating their role in enhancing battery performance metrics viz., capacity, life-span, and fast charging/discharging. This review provides the depth understanding on basic parameters require to design the affordable systems for ion-batteries especially with high storage ability. The future directions and potential avenues for leveraging two-dimensional materials to advance the next generation ion batteries, including emerging trends such as solid-state and sodium-ion batteries have also been clearly presented in this article.

Manganese-based (Mn2+/Mn3+) redox flow batteries are promising candidates for large-scale energy storage due to their relatively low cost and high positive potential (+1.51 V), enabling higher cell voltage and energy density compared to other aqueous flow batteries. However, the main challenge in long-term operation is the precipitation of MnO2 caused by Mn3+ disproportionation, which leads to capacity fade and reduced cycle life. Previous studies have shown that the use of additives or complexing agents within the manganese electrolyte reduces the disproportionation rate. In this work, we show that experimental conditions of the flow battery also affect the disproportionation rate, and consequently, battery performance. Lowering the upper cut-off voltage enhances electrolyte stability. Furthermore, shorter rest periods between charge and discharge improve battery efficiency, while long rest periods may result in a transition from reversible to irreversible behavior of MnO2 particles. Additionally, stable performance is observed when operating within a current density range of 50-100 mA cm-2. Moreover, a consistent increase in capacity is observed during cycling at current densities below 50 mA cm-2, opening new possibilities for system design and battery operation. Finally, an active species concentration of 0.5 M results in more stable performance and reduced precipitation.

Co-free and Li-rich nickel manganese layered oxides (LR-NMs) are considered next-generation cathode active materials for Li-ion batteries, owing to their high energy density at low cost. However, this materials class suffers from an open-circuit-voltage (OCV) hysteresis, resulting in low energy efficiency. In this study, LR-NMs with varying Li and Mn contents (Li_1+δ[Ni_xMn_y]_1-δO₂ with x/y = 0.65/0.35, 0.50/0.50, 0.35/0.65 (x + y = 1), and δ = 0.10–0.20) are prepared and characterized by X-ray diffraction. Their composition-dependent OCV hysteresis is determined by charge/discharge tests with intermittent OCV periods. We demonstrate that increasing Li and/or Mn content increases the contribution of the reversible anionic redox at similar discharge capacities, concomitant with an increased OCV hysteresis between charge and discharge in the cycles following the first-cycle activation. This is supported by a linear increase of the OCV hysteresis with the anionic redox contribution for the LR-NM materials synthesized and examined in this study (seven different compositions, each prepared at three different calcination temperatures). Considering that the increase of the OCV hysteresis with increasing overlithiation δ and/or Mn content y results in an intrinsically inferior energy efficiency, possible strategies for future LR-NM materials development are discussed.

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High chloride concentrations in industrial brines, such as those encountered in lithium extraction, critically challenge the localized corrosion resistance of structural alloys. This study investigates the effect of chloride concentration on the corrosion behavior of Zeron® 100 super duplex stainless steel (UNS S32760) by evaluating critical pitting temperature (CPT), critical crevice temperature (CCT), pitting potential (E_pit), and crevice repassivation potential (E_rep) across a wide range of chloride concentrations (1–8 M). CPT, CCT, and E_rep decreased logarithmically with chloride concentration, indicating a progressive reduction in localized corrosion resistance. At the highest Cl⁻ concentrations, E_rep falls below the corrosion potential, implying that spontaneous crevice corrosion is thermodynamically feasible under open-circuit conditions. SEM analysis reveals that increasing chloride concentration alters pit morphology and reduces the protective nature of the lacy cover. These findings provide new insights into the degradation mechanisms of Zeron® 100 in chloride-rich environments and highlight the importance of considering E_rep, in addition to CPT and E_pit, when predicting long-term performance.

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Highlights

• Systematic degradation of localized corrosion resistance was observed for Zeron® 100 (UNS S32760) SDSS with increasing chloride concentration, indicated by a logarithmic decrease in CPT, CCT, and E_rep.

• Repassivation potential decreased to values below the corrosion potential at high chloride concentrations, suggesting spontaneous crevice corrosion under open-circuit conditions.

• Pit and crevice morphologies evolved with Cl⁻ concentration, showing more porous lacy covers and deeper undercutting at higher Cl⁻ levels.

• Zeron 100’s performance limitations in extreme Cl⁻ environments highlight the importance of E_rep as a conservative and reliable parameter for long-term corrosion prediction in hydrometallurgical applications.

This study investigates the performance and structural stability of commercial micron-sized tin (Sn) particles as anode active material for sodium-ion batteries. Despite undergoing significant volume change during cycling, the Sn anode demonstrates stable capacity retention over 450 cycles in Sn/Na half-cells with an ether-based electrolyte. Initially fragmented Sn particles restructure into uniformly dispersed 1-micron sized spheres within the first 50 cycles. The restructuring process is hypothesized to result from the interplay between fragmentation and particle coalescence, preventing further pulverization. In the case of incomplete (de)sodiation, the voltage profile gradually evolves over cycling which suggests the development of an inhomogeneous morphology within the Sn electrode. To assess Na inventory loss during restructuring, a limited-inventory protocol was developed for Sn/Na cells, resulting in 95% of capacity retention over 100 cycles. Full NFPP/Sn coin cells only show 84% capacity retention after 100 cycles, which suggests additional parasitic reactions. An in situ pressure measurement was performed on a multi-layer NFPP/Sn pouch cell to monitor the stack pressure change. These results highlight the potential of Sn anodes and emphasize the need to address issues related to parasitic reactions and electrode volume expansion for their successful integration into practical sodium-ion batteries.

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The use of lithium intercalation electrodes (LIE) for recovering lithium from geothermal sources (containing ≤ 400 ppm of lithium) has the potential to revolutionize the lithium mining industry. This work proposes a conceptual scaled-up process for LIE, utilizing concentrated brine of 15 m³ h⁻¹ (384.32 mM or 2,666 ppm of lithium) obtained from a reverse osmosis unit. Given the high lithium concentration in the concentrated brine, testing LIE performance under high lithium content conditions (1 M LiCl) is essential. In this study, LiMn₂O₄ supported on vitreous carbon foam is evaluated as the positive electrode. Degradation of the intercalation-active material, LiMn₂O₄, was observed in acidic media, with significant manganese dissolution. In contrast, at near neutral pH, dissolution rate is considered lower. Faradaic efficiency in acid media showed 98% efficiency only during the first potentiostatic deintercalation run. Subsequent runs exhibited non-faradaic behavior, which was also attributed to manganese dissolution. To develop strategies for mitigating LiMn₂O₄ degradation, equilibrium diagrams for the Li-Mn-H₂O system (Poubaix Diagram) was constructed. In addition to propose a scaled-up process for lithium recovery from geothermal sources, this work investigates the performance of lithium intercalation under conditions relevant to large-scale operations.

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Operando optical methods are widely used for measuring the properties of battery electrodes under charge/discharge conditions and provide valuable insights into various phenomena. However, the need to gain optical access to the electrode of interest often requires a compromise, such that the electrochemical characteristics of the operando cell deviate from those in a conventional cell. One approach towards minimally invasive optical spectroscopy is the “through-hole” coin cell configuration in which the bottom electrode is optically accessed via a hole punched through the top electrode and separator, but the impact of this hole on the validity of the measurement has been given little consideration. Here we performed modelling of graphite and lithium nickel manganese cobalt oxide (LiNi0.6Mn0.2Co0.2O2; NMC622) electrodes in a Li-ion half-cell arrangement, to explore this through-hole configuration. We show that the presence of a 0.5 mm radius hole results in a non-uniform Li+ ion distribution in the electrode phase, but this can be reduced by decreasing the current, decreasing the hole size or increasing the separator thickness. The Li+ non-uniformity varies non-linearly with the average degree of electrode lithiation and is more extreme for a graphite electrode compared to NMC622 due to their contrasting voltage-charge profiles.

Studies have shown that using polydisperse active material particles can cause (i) heterogeneous electrochemical reactions within a battery electrode due to reactivity differences among different particle sizes, and (ii) heterogeneous electrode microstructures, leading to varied transport and charge transfer overpotentials throughout the electrode, exacerbating the reaction heterogeneity. The uneven utilisation of the battery electrode subjects certain electrode regions to greater electrochemical stress, with the risk of accelerated degradation. In this work, we focus on the impact of particle size distribution on battery electrode cyclability. First, we synthesised monodisperse polycrystalline LiNi1/3Mn1/3Co1/3O2 (NMC111) particles of two different sizes. Then, three electrodes with different particle size distributions (‘Small’, ‘Big’, ‘Mix’) were fabricated and examined as model systems. Contrary to our hypothesis that the ‘Mix’ electrode would exhibit the worst cyclability, the ‘Small’ electrode showed the best long-term cycling performance, followed by the ‘Mix’ electrode and then the ‘Big’ electrode. The discrepancy is attributed to the greater degree of particle cracking experienced by the big particles, disrupting solid-state charge transport within secondary particles, especially in the ‘Big’ electrode. Overall, this study provides new insights into synthesising monodisperse layered oxide cathodes and how both the average particle diameter and particle size distribution affect battery performance.

Manganese-based (Mn2+/Mn3+) redox flow batteries are promising candidates for large-scale energy storage due to their relatively low cost and high positive potential (+1.51 V), enabling higher cell voltage and energy density compared to other aqueous flow batteries. However, the main challenge in long-term operation is the precipitation of MnO2 caused by Mn3+ disproportionation, which leads to capacity fade and reduced cycle life. Previous studies have shown that the use of additives or complexing agents within the manganese electrolyte reduces the disproportionation rate. In this work, we show that experimental conditions of the flow battery also affect the disproportionation rate, and consequently, battery performance. Lowering the upper cut-off voltage enhances electrolyte stability. Furthermore, shorter rest periods between charge and discharge improve battery efficiency, while long rest periods may result in a transition from reversible to irreversible behavior of MnO2 particles. Additionally, stable performance is observed when operating within a current density range of 50-100 mA cm-2. Moreover, a consistent increase in capacity is observed during cycling at current densities below 50 mA cm-2, opening new possibilities for system design and battery operation. Finally, an active species concentration of 0.5 M results in more stable performance and reduced precipitation.

Tin (Sn) is a promising anode material for sodium-ion batteries (SIBs) due to its high theoretical specific capacity (847 mAh g-1) and volumetric capacity (6238 mAh cm-3). In addition, Sn is a commodity and can be readily sourced. However, alloy anodes tend to suffer from a low initial Coulombic efficiency (ICE) and severe capacity loss due to extensive volume expansion (~420% for Sn) during electrochemical cycling. In this work, commodity-sourced Sn is used (with an electrode active material composition of >99% Sn) to demonstrate how these traditional challenges can be overcome without major modifications. When paired with a NaCrO2 (NCrO) cathode in a full cell, a high specific energy of 178 Wh/kg and volumetric energy density of 417 Wh/L can be achieved. This work highlights the opportunities for alloy materials such as Sn to enable high energy density SIBs.

The formation of voids at the interface between metal (Li or Na) electrodes and solid electrolytes has critical implications for the development of robust solid-state batteries. Here, we examine vacancy diffusion in a metal electrode during electrochemical stripping to assess its role in the nucleation and growth of such voids. We develop one-dimensional solutions for the vacancy distribution within the electrode for an imposed stripping current. To develop a non-equilibrium vacancy concentration within the electrode, we assume that the redox reaction at the electrode/electrolyte interface imposes a vacancy flux into the electrode that is a fraction of the stripping current. Consequently, the vacancy concentration within the electrode can increase significantly above its initial equilibrium value and these vacancies might coalesce to form voids. However, there is a large energy cost to this non-equilibrium vacancy concentration in apparent violation of the Onsager/Rayleigh principle of the least dissipation of energy. Further, work is needed to understand if and how the redox reaction may provide the extra energy required to increase the vacancy concentration.

The influence of Sn alloying additions on the aqueous passivation behavior of Cu-Al alloys was revisited and found to function as a new third element effect in acidified 0.1 M Na₂SO₄ solution. The role of each element during the process of aqueous passivation was investigated using electrochemical and surface-sensitive ex-situ and in-operando spectroscopic techniques. The connection between passivation and the atomic arrangements of atoms in the solid-solution was supported by first principles’ based cluster expansion calculations and Monte Carlo simulations probing the chemical short-range order in the Cu-Al-Sn system. High purity Sn, like high purity Cu, did not passivate in the test environment, whereas high purity Al formed a passive film with a stable passive current density of 0.01 mA·cm⁻². Cu-xAl-Sn solid-solution alloys where x > 18 at.%, containing less than 3 at.% Sn additions exhibited lower corrosion rates than Cu-xAl alloys, brought by Al(III) and Sn(IV, II) unidentified complex oxides formation on the surface. A strong influence of Sn on Al(III) passivation was observed, i.e., strongly suggesting a third element effect type behavior. Possible governing processes explaining the stainless steel type corrosion behavior are discussed, providing insights for exploring novel synergies in the design of corrosion resistant alloys.

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.

There are an increasing number of studies regarding active electrode materials that undergo faradaic reactions but are used for electrochemical capacitor applications. Unfortunately, some of these materials are described as “pseudocapacitive” materials despite the fact that their electrochemical signature (e.g., cyclic voltammogram and charge/discharge curve) is analogous to that of a “battery” material, as commonly observed for Ni(OH)₂ and cobalt oxides in KOH electrolyte. Conversely, true pseudocapacitive electrode materials such as MnO₂ display electrochemical behavior typical of that observed for a capacitive carbon electrode. The difference between these two classes of materials will be explained, and we demonstrate why it is inappropriate to describe nickel oxide or hydroxide and cobalt oxide/hydroxide as pseudocapacitive electrode materials.

This work reports a quantitative analysis of the shuttle phenomenon in Li/S rechargeable batteries. The work encompasses theoretical models of the charge process, charge and discharge capacity, overcharge protection, thermal effects, self-discharge, and a comparison of simulated and experimental data. The work focused on the features of polysulfide chemistry and polysulfide interaction with the Li anode, a quantitative description of these phenomena, and their application to the development of a high-energy rechargeable battery. The objective is to present experimental evidence that self-discharge, charge-discharge efficiency, charge profile, and overcharge protection are all facets of the same phenomenon. © 2004 The Electrochemical Society. All rights reserved.

powders were synthesized under various conditions and the performance of the cathodes was evaluated using coin cells. The samples were characterized by X-ray diffraction, scanning electron microscope observations, Brunauer, Emmett, and Teller surface area measurements, particle-size distribution measurements, and Mössbauer spectroscopy. Ab initio calculation was used to confirm the experimental redox potentials and Mössbauer parameters. The choice of a moderate sintering temperature and a homogeneous precursor enabled nearly perfect utilization of >95% of the 170 mAh/g theoretical capacity at room temperature. There are two main obstacles to achieving optimum charge/discharge performance of (i) undesirable particle growth at and (ii) the presence of a noncrystalline residual phase at © 2001 The Electrochemical Society. All rights reserved.

This paper presents the results obtained on the electrochemical behavior of electrochemical capacitors assembled in nonaqueous electrolyte. The first part is devoted to the electrochemical characterization of carbon-carbon 4 cm² cells systems in terms of capacitance, resistance, and cyclability. The second part is focused on the electrochemical impedance spectroscopy study of the cells. Nyquist plots are presented and the impedance of the supercapacitors is discussed in terms of complex capacitance and complex power. This allows the determination of a relaxation time constant of the systems, and the real and the imaginary part of the complex power vs. the frequency plots give information on the supercapacitor cells frequency behavior. The complex impedance plots for both a supercapacitor and a tantalum dielectric capacitor cells are compared. © 2003 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.

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.

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.

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 , 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 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 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 ( at and ), 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.