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.

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.

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.

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.

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.

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.

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.

The development of new positive electrode materials is on route to increase the energy density of lithium-ion batteries (LIBs) for electric vehicle and grid storage applications. The performance of new materials is typically evaluated using hand-made half coin cells with the new material as the positive electrode and a piece of lithium foil for the negative. Whereas half coin cells are easy to make and can give reproducible data, they can fail to accurately predict how a material would perform in a full cell. The present work develops methods to prepare full coin cells, using graphite as the negative electrode material. Detailed instructions are provided to enable researchers to prepare their own high quality full coin cells with good reproducibility between cells. The precision of the hand-made full coin cells is compared with and found to approach the quality of machine-made, commercially produced full cells.

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

The dissolution of transition metals (TM) from the cathode and their subsequent deposition on the anode represent significant degradation mechanisms in lithium-ion batteries, particularly as the industry seeks to transition towards more sustainable and cost-efficient materials. In this work, the impacts of Mn, Fe, Ni, and Co depositions on the lithiated graphite anode were investigated using pouch storage experiments to simulate the migration-deposition process and compare it to electrodes from real cells. The morphology, chemical distribution, and oxidation states of deposited TMs were investigated by scanning electron microscopy, X-ray absorption spectroscopy, and scanning transmission X-ray microscopy. X-ray diffraction and half-cell studies for post-storage electrodes determined the lithium loss and impedance growth due to TM deposition. The impact of each TM on the lithiated graphite was found to be significantly different. Deposited Mn and Fe were fully metallic, preferred to accumulate on electrode surface, and caused severe delithiation of the graphite, while Ni and Co deposition were rather harmless. The results obtained from simulated TM-containing graphite electrodes closely corresponded with those extracted from cycled cells. This alignment enhances our understanding of the behavior of dissolved TM and paves the way for solutions aimed at mitigating capacity fade in commercial lithium-ion batteries.

Steam oxidation behavior of four general-purpose stainless steels, SUS430, SUS430LX, SUS430J1L, and SUS445J1, under humidified H₂ was investigated for application in solid oxide fuel cells (SOFCs). A Cr-rich surface oxide layer, preliminarily formed via pre-oxidation, effectively mitigated steam oxidation and suppressed elemental diffusion and oxide growth. After pre-oxidation at 900 °C for 2 h in air, the oxidation rate was less dependent on the gas composition, which was varied from 10%H₂O–90%H₂ to 50%H₂O–50%H₂, whereas it was strongly dependent on temperature. The structure of the surface oxide layer and direction of oxide growth differed depending on the alloy composition. The oxidation rate of SUS430J1L was similar to that of ZMG232G10 and relatively lower than those of three other stainless steels The Cr-rich oxide layer contained few defects, and its structure suppressed the diffusion of metal ions. Although a Si-rich oxide layer grew on the alloy side during the durability test performed at 727 °C for 1500 h, it had a lesser impact on the area specific resistance than that in SUS430. The microstructure of the Si-rich oxide layer, which featured other elements such as Cr, Mn, and Fe, maintained the electrical conduction path.

The abnormal expression of CYFRA21-1 is closely related to the development of non-small cell lung cancer (NSCLC), making its detection crucial for early diagnosis. In this study, we successfully constructed an electrochemical sensor based on nanopipettes and CRISPR/Cas12a for the detection of CYFRA21-1. We utilized an electrochemical three-electrode system to quantify the target by monitoring changes in electrochemical signals at the single-cell level. The small size of the nanopipettes, combined with the trans-cleavage activity of Cas12a, ensures reaction specificity while detecting CYFRA21-1 at the single-cell level. Experimental results demonstrated that the sensor exhibited a linear relationship with T-DNA concentration over the range of 1 fM to 1 μM, with a detection limit of 0.362 nM, indicating high sensitivity. The nanopipettes successfully detected CYFRA21-1 at the single-cell level, showing distinct signaling changes before and after the assay. Additionally, the sensor exhibited high specificity for CYFRA21-1 and was not affected by single-base or three-base mismatched DNA. In stability tests, the sensor demonstrated good reproducibility and stability. These properties render this electrochemical sensor a promising tool for important applications in disease diagnosis and monitoring.

Heterostructure engineering has proven its efficiency in the field of water electrolysis by accelerating reaction kinetics and boosting overall activities. Here, a heterostructure interface between a metallic alloy and its corresponding oxidized species (metal oxide and oxy/hydroxide) was constructed. Ni₃Sn₄ alloy was electrodeposited using the dynamic hydrogen bubble template (DHBT) method, followed by an electrochemical passivation process in an alkaline medium to grow a top layer of oxidized species, resulting in a heterojunction interface (NiSnO_xH_y/Ni₃Sn₄). Electrochemical and surface analyses were employed to describe the formed interface. NiSnO_xH_y/Ni₃Sn₄ electrocatalyst showed enhanced activity towards the hydrogen evolution reaction (HER) in 1 M KOH, requiring only ‒166 mV overpotential to support a current density of 10 mA cm⁻², compared to −409, −275, and −367 mV at Sn, Ni, and non-passivated Ni₃Sn₄ films, respectively, demonstrating the prominent superior intrinsic characteristics of the developed interface. The boosted catalysis by NiSnO_xH_y/Ni₃Sn₄ is presumably attributed to a promoted dissociative step of water with concurrent prevention of the poisoning of H adsorption sites by hydroxide ions generated during HER. The proposed electropassivation approach for designing heterostructure interfaces has shown effectiveness in promoting HER rate in alkaline media, besides its economic feasibility as a simple, low-cost, and binder-free method.

This paper discusses factors controlling electrochemistry-induced deposition of a zeolitic imidazolate framework-8 (ZIF-8) film on a planar substrate that is placed under an electrode. This method, which was recently demonstrated by us [T. Ito, et al. Cryst. Growth Des., 23, 6369 (2023)], provides a simple means to form a ZIF-8 film having lateral dimensions replicating those of a working electrode on an underlying substrate. We reported the effects of applied cathodic potential, electrode–substrate distance, and deposition time on the film formation, and proposed a mechanism involving cathodic base generation at a working electrode that promoted ligand deprotonation to form intermediate species, followed by their diffusion toward an underlying substrate. Here, we discuss details on the deposition mechanism by investigating the influences of other factors on the film deposition. We have investigated the effects of precursor concentration on film formation, and clarified that O₂ is a probase, rather than H₂O. We have also shown the influences of substrate surface properties controlled by self-assembled monolayers on film thickness and morphology. Most notably, we successfully demonstrated the formation of microscale ZIF-8 films using an ultramicroelectrode, revealing the applicability of the electrochemistry-induced method for micropatterned film deposition on an underlying substrate.

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Electrolysis serves as an effective technique for metal preparation, with the electrolytic cell being the fundamental apparatus. The design of the electrolytic cell significantly influences the mass transfer process. Therefore, it is crucial to create an appropriate structure for the electrolytic cell to minimize energy consumption during electrolysis. Given the unique characteristics of the metals involved, the configurations of electrolytic cells vary accordingly. This article examines primary metals produced through electrolysis, such as aluminum and alkali metals, and discusses advancements in research and design principles related to electrolytic cell structures. It also compares various types of electrolytic cells and suggests strategies for structural optimization. Additionally, the role of simulation in the design of electrolytic cells is emphasized. Finally, the article addresses the challenges encountered by electrolytic cells in industrial settings and offers recommendations for structural improvements.

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The opioid crisis has emerged as a critical public health issue, characterized by the widespread misuse, addiction, and adverse societal impacts of opioid substances. Addressing this multifaceted crisis demands innovative approaches, and the field of forensic science has increasingly turned to electrochemical methods as a powerful tool in the battle against opioids. Here we provide an overview of the significant role played by electrochemical techniques in the detection, analysis, and monitoring of opioids. By harnessing the capabilities of electrochemical sensors, nanomaterial-based platforms, and microfluidic devices, forensic scientists have achieved breakthroughs in opioid detection, offering higher sensitivity, specificity, and rapidity than traditional methods. We explore the latest advancements and applications of electrochemical techniques in forensic opioid analysis, highlighting their potential to revolutionize not only the investigative process but also the management of opioid-related crises. With an emphasis on real-time, on-site, and non-invasive detection, we underscore the importance of electrochemical techniques as a vital component in combating the opioid epidemic and contributing to public safety and well-being.

For many years since Gurney introduced quantum mechanics to electrochemistry, models and calculations assumed bonding and other properties at the electrochemical interface may be calculated with adequate accuracy at the potential of zero charge (PZC) and that the effect of potential lies solely in controlling the energy of the electron involved in the transfer, which comes from or goes to an external energy level. The energy of the electron is assigned to the Fermi energy, E_f, of the electrode for the particular potential being modeled. This is done in the Butler-Volmer theory as well as in several quantum mechanical modeling procedures that are introduced here. Though the PZC in fact changes as the identity, amount, and structures of molecules chemically bonded to the electrode are varied during calculations using these models, there is no control of the electrode potential in the calculations. The past two decades have seen the development of computer codes that can incorporate controlled incremental surface charging with polarizable electrolyte models that compensate it, resulting in zero net interface charge. Calculations using these codes provide accurate predictions of the potential-dependent energies of reactants and products, reversible potentials, and electron transfer activation energies.

Due to the advantages of environmental friendliness and high energy density, fuel cells have broad application prospects in many fields, such as automobiles, ships, aerospace, etc However, commercial applications of fuel cells also face challenges of durability and reliability, especially in shock and vibration environments. Here, the electrochemical and mechanical behaviours of fuel cells under vibration environments are described, and the effects of vibration and shock conditions on the electrochemical, mechanical, water and gas transport, and durability performance of fuel cells are systematically reviewed, involving the variation laws of assembly torque, sealing, relative slippage between cells, water and gas transport, electrical resistance, and membrane electrodes. In addition, the methods that can mitigate the effects of vibration on fuel cells in existing studies are summarised. Finally, discussions and perspectives on the research methods of fuel cell performance under vibration are presented. It is hoped that the review can provide a systematic comprehension and direction for vibration protection of fuel cells.

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Highlights

• Vibration and shock have a negative impact on fuel cell performance in most cases.

• Fuel cell performance degradation is affected by the coupling of multiple phenomena.

• Specific vibration levels improve cell performance by facilitating water management.

• Monitoring and vibration isolation/damping enable vibration protection of fuel cells.

Renewable energy systems will need large-scale energy storage to ensure reliability and provide power when and where it is needed. Even though lithium-ion batteries are increasingly used for large-scale storage, their costs and competition in terms of materials needed for electric vehicles are driving the need for alternative batteries for stationary energy storage systems. Molten sodium-ion batteries that operate at intermediate temperatures, approximately 150 °C or less, offer an abundant and cost-effective solution to our energy storage issues. This review paper highlights the materials, enhancements, and performance of molten Na–ion batteries that operate at temperatures at or below 150 °C for use in energy storage systems as well as an outlook on future improvements for this energy storage system.

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.

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

Highlights

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

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

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

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

The effect of different waveforms on the performance of pulsed current cathodic protection in preventing crevice corrosion resulted from the creation of a holiday at the disbonded coating was investigated numerically. In order to achieve this goal, the oxygen concentration gradient, pH, sodium ion concentration gradient, potential distribution, and distribution of net current density were analyzed. The findings show that the ramp waveform is capable of reducing the oxygen concentration gradient along the crevice to the lowest possible level in comparison with other waveforms. Based on this, the oxygen concentration cell was moderated to the greatest level, and as a result, the potential gradient along the crevice was decreased to a greater extent compared to other waveforms.

Anion-exchange membrane water electrolyzers (AEM-WE) have been identified as a promising solution to deliver green hydrogen at a lower cost than alkaline water electrolyzers (AWEs) and proton-exchange membrane water electrolyzers (PEM-WEs). However, scaling AEM-WE is limited by high voltage degradation rates which can become amplified and more complicated during operation as components within the membrane electrode assembly (MEA) evolve and interact with one another. These phenomena necessitate testing protocols that capture the degradation of individual MEA components in-situ. Herein, an edge-type reference electrode and a novel flow plate design enabled decoupling of anode and cathode degradation over stability tests >200 hours. A critical assessment of the overpotential measurements is provided, utilizing half-cell impedance measurements to highlight the effects of electrode misalignment. 3-electrode cyclic voltammetry is presented as an effective in-situ tool to evaluate electrode degradation. These findings demonstrate the utility of edge-type reference electrode configurations in stability tests for the development of commercial scale AEM-WE.

Continuous glucose monitoring (CGM) is crucial for managing diabetes and food/pharmaceutical quality control because of the clinical and industrial relevance of glucose. Various electrochemical and optical techniques have been explored for the detection of glucose. Carbon dots (CDs), nanomaterials with high surface areas and active sites, show promise as nanozymes for CGM because of their tunable size, shape, and surface properties. This review critically evaluates the impact of CD oxidation states and surface residues on the sensitivity and selectivity of CGM. CD nanocomposites incorporating metals, metal oxides, and metal sulfides were also assessed. Special focus is placed on advancing the performance of next-generation CGM systems in terms of efficiency and reliability. The interactions between CDs and various composite configurations were examined to identify opportunities for enhancing current CGM technologies. This comprehensive analysis of the evolving biosensor landscape aims to provide insights that support innovation in glucose monitoring for patient care and industrial applications.

Accurate and sensitive environmental pollution detection is essential for addressing the health risks associated with volatile organic compounds (VOCs) emitted from industrial activities, household products, and vehicles. However, achieving high selectivity and stability under diverse environmental conditions poses significant challenges. Consequently, there is a pressing need for innovative materials that can enhance gas-sensing performance. MXene, a class of two-dimensional transition metal carbides and nitrides, have emerged as promising candidates owing to their exceptional electrical, mechanical, and chemical properties. This review explores various synthesis techniques of MXene, including top-down and bottom-up approaches, highlighting the impact of these methods on the structural and functional properties of MXene. It also examines the combination of MXene with metal oxides to create nanocomposites, focusing on their enhanced performance in VOC sensing applications. The synergistic effect of MXene and metal oxides is analyzed, demonstrating improved sensitivity, selectivity, and response times in VOC detection. MXene-metal oxide nanocomposites use the large surface area, conductivity, and chemical reactivity of MXene, as well as the catalytic capabilities of metal oxides, to provide excellent sensing capability. This article discusses the improved performance of nanocomposites, their production progress, and recent advancements, while also reviewing challenges and providing insights for future research.

We present a physical model of the cathode catalyst layer morphology which simulates the electrochemically active catalyst surface area at varying degrees of humidification. The model considers pore, particle and ionomer distributions and resulting interfaces on the nanoscale to create a unique mathematical representation of each material. Specifically, the model discriminates between catalyst particles on the support surface and inside primary pores of the support and their respective connection to the proton-conducting phase. 
 Catalyst particles may be protonically activated by coverage with ionomer or water or be protonically inaccessible. The exact configuration depends on the particle size and location as well as the cell operating conditions, sensitizing the simulated catalyst utilization to these properties.
 Model results are compared against data for five samples with different support materials and ionomer loadings manufactured in-house. Further, trends in catalyst utilization which were observed in recent literature are reproduced with the model. This work provides a comprehensive analysis of material configurations and simulations at begin of test. In Part II, the presented model is integrated into a degradation model to predict the evolution of the electrode morphology and catalyst utilization during ageing.

The dissolution of transition metals (TM) from the cathode and their subsequent deposition on the anode represent significant degradation mechanisms in lithium-ion batteries, particularly as the industry seeks to transition towards more sustainable and cost-efficient materials. In this work, the impacts of Mn, Fe, Ni, and Co depositions on the lithiated graphite anode were investigated using pouch storage experiments to simulate the migration-deposition process and compare it to electrodes from real cells. The morphology, chemical distribution, and oxidation states of deposited TMs were investigated by scanning electron microscopy, X-ray absorption spectroscopy, and scanning transmission X-ray microscopy. X-ray diffraction and half-cell studies for post-storage electrodes determined the lithium loss and impedance growth due to TM deposition. The impact of each TM on the lithiated graphite was found to be significantly different. Deposited Mn and Fe were fully metallic, preferred to accumulate on electrode surface, and caused severe delithiation of the graphite, while Ni and Co deposition were rather harmless. The results obtained from simulated TM-containing graphite electrodes closely corresponded with those extracted from cycled cells. This alignment enhances our understanding of the behavior of dissolved TM and paves the way for solutions aimed at mitigating capacity fade in commercial lithium-ion batteries.

The abnormal expression of CYFRA21-1 is closely related to the development of non-small cell lung cancer (NSCLC), making its detection crucial for early diagnosis. In this study, we successfully constructed an electrochemical sensor based on nanopipettes and CRISPR/Cas12a for the detection of CYFRA21-1. We utilized an electrochemical three-electrode system to quantify the target by monitoring changes in electrochemical signals at the single-cell level. The small size of the nanopipettes, combined with the trans-cleavage activity of Cas12a, ensures reaction specificity while detecting CYFRA21-1 at the single-cell level. Experimental results demonstrated that the sensor exhibited a linear relationship with T-DNA concentration over the range of 1 fM to 1 μM, with a detection limit of 0.362 nM, indicating high sensitivity. The nanopipettes successfully detected CYFRA21-1 at the single-cell level, showing distinct signaling changes before and after the assay. Additionally, the sensor exhibited high specificity for CYFRA21-1 and was not affected by single-base or three-base mismatched DNA. In stability tests, the sensor demonstrated good reproducibility and stability. These properties render this electrochemical sensor a promising tool for important applications in disease diagnosis and monitoring.

This paper discusses factors controlling electrochemistry-induced deposition of a zeolitic imidazolate framework-8 (ZIF-8) film on a planar substrate that is placed under an electrode. This method, which was recently demonstrated by us [T. Ito, et al. Cryst. Growth Des., 23, 6369 (2023)], provides a simple means to form a ZIF-8 film having lateral dimensions replicating those of a working electrode on an underlying substrate. We reported the effects of applied cathodic potential, electrode–substrate distance, and deposition time on the film formation, and proposed a mechanism involving cathodic base generation at a working electrode that promoted ligand deprotonation to form intermediate species, followed by their diffusion toward an underlying substrate. Here, we discuss details on the deposition mechanism by investigating the influences of other factors on the film deposition. We have investigated the effects of precursor concentration on film formation, and clarified that O₂ is a probase, rather than H₂O. We have also shown the influences of substrate surface properties controlled by self-assembled monolayers on film thickness and morphology. Most notably, we successfully demonstrated the formation of microscale ZIF-8 films using an ultramicroelectrode, revealing the applicability of the electrochemistry-induced method for micropatterned film deposition on an underlying substrate.

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Fire and deflagration that might occur in high-energy content/high-power lithium ion (Li-ion) batteries are due to propagation of thermal runaway (TR) from just a single failing "trigger" cell to the remaining fully-functional cells. Here we describe iterative housing designs of a multi-cell Li-ion battery module with the goal of preventing cell-to-cell TR propagation from a trigger cell to the remaining cells in the module. After series of experimental tests and iterations, we demonstrate a battery module, containing eight fully charged 18650 cells connected in series, that prevents TR propagation from one externally-heated trigger cell. We demonstrate further that even after TR of an individual cell in that module, all remaining cells continue to maintain nameplate cell voltage and cell capacity after the event.

Anion-exchange membrane water electrolyzers (AEM-WE) have been identified as a promising solution to deliver green hydrogen at a lower cost than alkaline water electrolyzers (AWEs) and proton-exchange membrane water electrolyzers (PEM-WEs). However, scaling AEM-WE is limited by high voltage degradation rates which can become amplified and more complicated during operation as components within the membrane electrode assembly (MEA) evolve and interact with one another. These phenomena necessitate testing protocols that capture the degradation of individual MEA components in-situ. Herein, an edge-type reference electrode and a novel flow plate design enabled decoupling of anode and cathode degradation over stability tests >200 hours. A critical assessment of the overpotential measurements is provided, utilizing half-cell impedance measurements to highlight the effects of electrode misalignment. 3-electrode cyclic voltammetry is presented as an effective in-situ tool to evaluate electrode degradation. These findings demonstrate the utility of edge-type reference electrode configurations in stability tests for the development of commercial scale AEM-WE.

We present a physical model of the cathode catalyst layer morphology which simulates the electrochemically active catalyst surface area at varying degrees of humidification. The model considers pore, particle and ionomer distributions and resulting interfaces on the nanoscale to create a unique mathematical representation of each material. Specifically, the model discriminates between catalyst particles on the support surface and inside primary pores of the support and their respective connection to the proton-conducting phase. 
 Catalyst particles may be protonically activated by coverage with ionomer or water or be protonically inaccessible. The exact configuration depends on the particle size and location as well as the cell operating conditions, sensitizing the simulated catalyst utilization to these properties.
 Model results are compared against data for five samples with different support materials and ionomer loadings manufactured in-house. Further, trends in catalyst utilization which were observed in recent literature are reproduced with the model. This work provides a comprehensive analysis of material configurations and simulations at begin of test. In Part II, the presented model is integrated into a degradation model to predict the evolution of the electrode morphology and catalyst utilization during ageing.

A treatment is developed for porous electrodes consisting of porous agglomerates, with the porous agglomerates consisting of solid (primary) particles of active material. With the use of the multi-site, multi-reaction formulation, gradients of the chemical potential of Li are the driving force for solid-state diffusion, and the different Li species and reaction sites are employed in the electrochemical kinetics equations. The method is applied to the Li-Si electrode system, including the impact of protective coatings over the active materials. The numerical analysis treats the full pseudo-three-dimensional problem, and histories and profiles of the potentials and concentrations are elucidated. The overall procedure can facilitate rational battery design and construction, including attendant trade-offs for selection of key physical dimensions and material alternatives that govern the cell performance.

Lower anode catalyst loadings and higher current densities are essential to lowering the levelized cost of H₂ production via proton exchange membrane water electrolysis (PEMWE). However, these approaches can induce significant durability challenges. Here, we show that cell degradation can include large reversible voltage losses across a variety of conditions, including low loadings and high currents. Although there is limited published discussion of reversible voltage losses in PEMWE, we demonstrate that they are an important consideration in cell efficiency and durability. Understanding the mechanisms of reversible losses and developing mitigation strategies is therefore a key priority for enabling low-cost PEMWE.

Due to degradation or by design, the cathode electrode of a proton exchange membrane fuel cell (PEMFC) can exhibit an inhomogeneous Pt-distribution that can affect the assessment of electrode properties by electrochemical impedance spectroscopy (EIS), such as proton transport resistivity (R_p). In this study, bilayer cathodes of varying Pt loadings (Low-Low, Low-High, High-Low, and High-High) were fabricated to simulate homogeneous and heterogeneous Pt distributions. Hereby, the Low-High configuration mimics an aged electrode with a Pt-depleted region near the membrane and a Pt-rich area near the gas diffusion layer. Potentiostatic EIS (PEIS) spectra were compared at two bias potentials. At 0.2 V, where the PEIS measurement is strongly influenced by the pseudo-capacity of hydrogen underpotential deposition (H_upd) on the Pt surface, impedance spectra for nonhomogeneous bilayers deviated significantly from homogeneous bilayers. Conversely, at 0.45 V where the double-layer capacitance of the carbon support dominates, the EIS of homogeneous and inhomogeneous samples overlapped. Aging a commercial sample via load/unload accelerated stress tests resulted in a shift to higher values for R_p assessed at 0.2 V, while the spectra at 0.45 V remained constant, matching the Low-High bilayer sample. These findings highlight the importance of considering the Pt distribution when assessing electrode properties.

Volume and subsequent porosity changes of lithium-ion cells during charge-discharge cycles are major challenges in the development of high-performance and long-lasting batteries. This work presents a novel coupled electrochemical-mechanical modeling approach to describe porosity changes due to intercalation and external compression. Based on the Doyle-Fuller-Newman model, the electrochemical model is extended by incorporating a mechanical model grounded in solid mechanics. The elasticity of the anode, separator, and cathode is modeled as poroelastic to account for the non-linear stress-strain behavior of these porous materials. A porosity model to calculate the local changes in porosity is introduced and discussed. The coupled model is validated against a 70.2 Ah cell regarding cell voltage, reversible cell swelling, and pressure increase for C-rates between C/20 and 1C, achieving a root-mean-squared error ≤12mV in cell voltage and <7% in reversible cell swelling. Simulation studies reveal that mechanical aspects significantly impact electrochemical performance, potentially leading to earlier lithium plating. Furthermore, the mathematical formulation shows that porosity changes alone have minimal impact on performance, and that effective mass transport should be updated based on porosity changes. The model prediction regarding internal states like porosity and volume changes aligns with the literature.