The 50 most-cited articles in Journal of The Electrochemical Society, 2021

Forecasting the health of a battery is a modeling effort that is critical to driving improvements in and adoption of electric vehicles. Purely physics-based models and purely data-driven models have advantages and limitations of their own. Considering the nature of battery data and end-user applications, we outline several architectures for integrating physics-based and machine learning models that can improve our ability to forecast battery lifetime. We discuss the ease of implementation, advantages, limitations, and viability of each architecture, given the state of the art in the battery and machine learning fields.

All-solid-state lithium batteries have the potential to provide increased energy and power density compared to conventional lithium-ion batteries with a liquid electrolyte. The charge transport within solid electrolyte-based composite cathodes determines the C-rate capability and ultimately the overall performance of a solid-state cell, making it one of the key remaining challenges. In this study, the charge transport in composite cathodes composed of Li 6 PS 5 Cl and NCM-622 is analyzed and characterized in terms of the effective ionic and electronic partial conductivities. The correlations between these effective conductivities, the microstructure of the composite cathodes, and the all-solid-state cell performance are revealed. By quantifying these correlations, bottlenecks for charge transport in composite cathodes are identified and strategies to optimize the cell performance are developed. The optimization potential of these strategies is demonstrated exemplarily by tuning electronic and ionic charge transport pathways using high active material loadings and an adjusted solid…

The rapid adoption of electric vehicles (EVs) and the evolving needs of portable electronic devices has intensified the need for enhanced state diagnosis of Li-ion batteries (LIBs). As the applications for LIBs continue to grow, so too does their operational requirements; ranging from faster charging and improved safety to optimized energy control and extended lifespan. In order to keep pace with the growing requirements of LIBs, improvements in the monitoring of battery states must be achieved. Although electrochemical impedance spectroscopy (EIS) has existed since the 1960’s, its potential as a diagnosis tool has only received widespread attention in recent years. In this paper, a detailed review on the applicability of impedance measurements for the estimation of the vital battery parameters of state of charge (SOC), state of health (SOH) and internal temperature (IT) has been performed.

The proportion of new energy power generation gets higher and higher, due to the depletion of fossil energy resources. However, new energy power is generally unstable, so that it is necessary to use energy storage batteries to balance the power peak and valley. Although lithium-ion batteries have been widely used in various fields, in particular for large-scale energy storage, the low abundance of lithium in the earth crust makes it untenable to meet the ever-intense future demand. Sodium ion batteries, which have similar energy storage mechanism to lithium-ion batteries, have attracted significant attentions due to their abundant raw material resources, low cost, and fairly high energy densities. Layered transition metal oxides are a class of the most promising cathode materials for sodium ion batteries, owing to their high theoretical specific capacities, good conductivity, and fast diffusion kinetics. In this paper, we conduct a comprehensive review of the electrochemical performance, structural characteristics, performance shortcomings and modification technologies about the O3-…

The separator is a critical component for the performance of alkaline water electrolysis as it ensures the ionic contact between the electrodes and prevents the product gases from mixing. While the ionic conductivity of the separator affects the cell voltage, the permeability of the dissolved product gases influences the product gas impurity. Currently, diaphragms are used as separators, the pore system of which is filled with the electrolyte solution to enable the exchange of ions. The breakthrough of the gas phase can be prevented up to a specific differential pressure. A drawback of diaphragms is the requirement of a highly concentrated electrolyte solution to maintain a high ionic conductivity. The usage of anion-exchange membranes could solve this problem. However, the long-term stability of such materials remains unproven. This study compares two pre-commercial diaphragms, an anion-exchange membrane, and an ion-solvating membrane with the state-of-the-art diaphragm ZirfonTM Perl UTP 500. Besides physical characterization, the material samples were evaluated electrochemically…

Electrochemical, chemiresistive and wearable sensors based on tin oxide (SnO2) were investigated for chemical sensing applications. There is an increased usage of SnO2 as modifier electrode materials because of its astonishing features of thermal stability, biocompatibility, excellent bandgap, cost effective and abundant availability. The surface of working electrode is modified by nanomaterials of SnO2 in combination with various metals, semiconductors and carbon derivatives for improved sensing performance. Various voltammetric and amperometric techniques were involved in studying the electrochemical properties and behaviour of the anlaytes at the surface of modified electrodes. This review focused on some recent works that provides an overview of the applications of SnO2 nanomaterials for the development of chemiresistive, electrochemical, and wearable sensors.

In this study, a commercial IrO 2 /TiO 2 catalyst (75 wt% Ir, named “Benchmark”) for the oxygen evolution reaction (OER) is compared to a newly developed IrO(OH) x /TiO 2 catalyst (45 wt% Ir, named “P2X”). Due to its lower Ir packing density and higher OER activity vs the Benchmark catalyst (440 vs 12 A g Ir −1 at 1.43 V iR-free ), the P2X catalyst shows an improved PEM (proton exchange membrane) water electrolyzer performance at ≈9 times reduced Ir loading, however, only if a platinum-coated porous transport layer (PTL) at the anode is used. While the performance of membrane electrode assemblies (MEAs) with the Benchmark catalyst is unaffected when using an untreated titanium PTL, MEAs with the P2X catalyst perform poorly, which can be attributed to a contact resistance at the anode/PTL interface due to the low electrical conductivity of the P2X catalyst (0.7 S cm −1 ) vs the Benchmark catalyst (416 S cm −1 ) and the passivation of the Ti-PTL. A heat treatment procedure is used to transform the amorphous IrO(OH) x of the P2X catalyst into crystalline IrO x and, hence, increases its…

Lithium-ion batteries cell thickness changes as they degrade. These changes in thickness consist of a reversible intercalation-induced expansion and an irreversible expansion. In this work, we study the cell expansion evolution under variety of conditions such as temperature, charging rate, depth of discharge, and pressure.A specialized ?fixture was used to keep the cells at a constant pressure during cycling, while measuring the thickness change both within a cycle and the cumulative growth over many cycles. The changes in positive and negative electrode capacity and stoichiometric range can be diagnosed from the evolution of the reversible expansion. The changes in the reversible expansion if combined with the voltage, lead to a higher-confi?dence estimation of cell health parameters important for lifetime prediction and adoptive battery management such as asymmetric charge/discharge power limits. This study raises the importance of monitoring the expansion for enabling advanced and more-informed health diagnostics of lithium-ion batteries.

Optimizing the performance of the lithium metal anode is required to enable the next generation of high energy density batteries. Anode-free lithium metal cells are particularly attractive as they facilitate the highest energy density cell architecture. In this work, we investigate the performance of anode-free cells cycled under different protocols. We demonstrate the impact of charge and discharge current density with three different cycling conditions: a symmetric charge-discharge, an asymmetric faster charge and an asymmetric slower charge. We show that the relative rate of charge vs discharge is more important than the absolute current densities, and that cycling with an asymmetric slower charge protocol is optimal in agreement with previous studies on cells with lithium metal anodes. We also examine the effect of depth of discharge and demonstrate how the lower voltage cut-off can be chosen to form a lithium reservoir in situ. We show that the capacity of the lithium reservoir significantly benefits lifetime for cells cycled with a limited depth of discharge. Finally, we…

Many solid-state devices, especially those requiring anion conduction, often add a supporting electrolyte to enable efficient operation. The prototypical case is that of anion-exchange-membrane water electrolyzers (AEMWEs), where addition of an alkali metal solution improves performance. However, the specific mechanism of this performance improvement is currently unknown. This work investigates the functionality of the alkali metal solution in AEMWEs using experiments and mathematical models. The results show that additional hydroxide plays a key role not only in ohmic resistance of the membrane and catalyst layer but also in the reaction kinetics. The modeling suggests that the added liquid electrolyte creates an additional electrochemical interface with the electrocatalyst that provides ion-transport pathways and distributes product gas bubbles; the total effective electrochemical active surface area in the cell with 1 M KOH is 5 times higher than that of the cell with DI water. In the cell with 1 M KOH, more than 80% of the reaction current is associate with the liquid…

Over the past decade, the development of amperometric sensors and biosensors using microfabrication techniques has gained considerable attention. This interdisciplinary approach aims at bringing together scientific fields such as: chemistry, physics, engineering and biology to achieve devices’ miniaturization, integration and automatization. Among the technologies that have been reviewed for the fabrication of the microelectrodes, the most common are: soft lithography and microfabrication techniques, such as physical vapor deposition of different metals, photolithography, chemical wet etching method and anodic bonding process. The required parameters in the design of a microfabricated electrode array, such as inter-electrode distance, the three-electrode system, and the role of each electrode have been intensively discussed. This review provides an overview about the state-of-the-art microfabrication devices and their applications, as well as the recent advances in the fabrication of microelectrodes as transducers for amperometric sensors, immunosensors and biosensors with various…

The highly-efficient, low-cost, large-scale production of green hydrogen by means of electrolysis is urgently needed for achieving a decarbonized energy supply. Alkaline water electrolysis is a wellestablished technology with relatively low costs which does not require scarce noble metal catalysts, but it suffers from low current densities. Increasing the operating temperature can allow this limitation to be overcome. This article summarizes both long-standing and recent developments in alkaline water electrolysis at increased temperature and sheds light on the challenges and unique opportunities of this approach. It is found that electrochemical improvements induced by higher temperature enable competitive current densities and offer unique possibilities for thermal management. The selection and development of stable materials, catalysts, and diaphragms is challenging, but some have proven long-term stability up to at least 150 °C and promising candidates are available at up to 200 °C. Further research will allow the present challenges to be overcome by understanding and improving…

Nickel-rich lithium nickel-manganese-cobalt oxide cathodes, in particular Li(Ni 0.8 Mn 0.1 Co 0.1 )O 2 (NMC811), are currently being commercialized as next generation cathode materials, due to their increased capacities compared to current materials. Unfortunately, the higher nickel content has been shown to accelerate cell degradation and a better understanding is needed to maximize cell lifetimes. NMC811/graphite cells were tested under stressed conditions (elevated temperature and cell voltages) to accelerate degradation focusing on transition metal (TM) dissolution from the cathode. Increasing the cell temperature, upper cut-off voltage (UCV) and number of cycles all accelerated capacity fade and diffraction studies showed that under stressed conditions, additional degradation mechanisms beyond lithium loss to the SEI are present. Significant TM dissolution and subsequent deposition on the graphite anode is seen, particularly at stressed conditions. The concentration of TMs in the electrolyte remained invariant with cycling conditions, presumably reflecting the limited…

The solid electrolyte interphase (SEI) acts as a protection layer on the surface the anodes of lithium ion batteries to prevent further electrolyte decomposition. Understanding the fundamental properties of the SEI is essential to the development of high capacity silicon anodes. However, the detailed mechanism of the generation of the evolution of the SEI on the silicon anodes is not fully understood. This manuscript reviews our recent investigations of the SEI on silicon anodes. We have studied the fundamental formation mechanism of the SEI on silicon anodes, along with the evolution which occurs to the SEI upon cycling.

This study reveals the source of discrepancy between the lifetime of oxygen evolution reaction (OER) catalysts determined by rotating disk electrode (RDE) measurements vs that obtained in a membrane electrode assembly (MEA) in an electrolyzer. We show that the accumulation of microscopic oxygen bubbles in the pores of the electro-catalyst layer during the OER takes place in both RDE and MEA measurements. However, this accumulation was found to be much more significant in RDE measurements, where the shielding of almost all of the catalyst active sites by gas bubbles leads to rapid performance deterioration. This decrease in performance, albeit largely reversible, was found to also induce irreversible catalyst degradation, which could be avoided if the accumulation of microscopic bubbles is prevented. This type of artefact results in vastly under-estimated catalyst lifetimes obtained by RDE experiments, resulting in values that are orders of magnitude shorter than those obtained using MEA measurements, and a hypothesis for this discrepancy will be proposed. Therefore, electrochemical…

For a long time, the corrosion problem of materials has been an essential factor in restricting high-tech and national economic development. As an effective means of corrosion protection, surface coatings have drawn extensive attention in the field of material corrosion. Performance improvement and a new composition system of high-entropy alloys (HEAs) have made HEA coatings a research hotspot. HEA coatings inherit the “four core effects” of bulk HEAs, especially high entropy and sluggish diffusion, making high-quality coatings exhibit outstanding corrosion resistance. At present, many reports have focused on the performance of HEA coatings in the field of severe corrosion environments. This article reviews the process parameters and different element contents on the corrosion resistance of HEA coatings in recent years. This paper describes the advantages and excellent corrosion resistance of HEA coatings, including the preparation methods and classification of HEA coatings. Moreover, exploration of the corrosion behavior and the mechanism of HEA coatings are described, and the…

The galvanostatic intermittent titration technique (GITT), introduced in 1977 by Weppner and Huggins, provided a readily accessible means to measuring the chemical diffusion coefficient of electrochemical electrode materials. The method continues to be widely used today, but the reported diffusivity values are highly inconsistent, ranging as much as four orders of magnitude for some Li layered oxide compositions. Even qualitative trends of diffusivity are inconsistent, suggesting significant flaws in the implementation of the method. Other variants of the GITT method also suffer from similar inconsistency problems. Here we identify numerous sources of significant error including composition-dependent reaction overpotentials, mathematical flaws in the relaxation analysis methods, finite-size and non-planar geometry effects, inter-particle inhomogeneity issues, early transient effects, and surface area uncertainties. We propose a simple relaxation analysis scheme using the time variable t relax + τ − t relax , where t relax is relaxation time and τ is the galvanostatic pulse duration.…

Among energy storage technologies available or currently being developed, one of the most promising and attractive electrochemical system is the vanadium redox flow battery (VRFB). One of the key components in VRFB is the membrane required to separate the positive and negative half-cells. The role of this membrane is to prevent cross-mixing of vanadium ions while allowing the transport of certain ions to maintain the electrolytes’ electro-neutrality. Such a membrane represents a sizeable fraction of the system’s total cost while significantly affecting performance. Current research mostly consists of developing high-performance membranes offering high ionic conductivity, low permeability to vanadium ions, and good chemical and mechanical stability. A lower membrane cost is also desirable in order to reduce the overall system costs. This paper provides a comprehensive review of VRFB membranes and recent developments to allow for a better understanding of VRFB membranes’ characterization techniques and their different manufacturing methods, while exploring materials suitable as VRFB…

One promising way of compensating for the repeated volume expansion and contraction of silicon as an anode active material in lithium ion batteries (LIBs) is to embed silicon within a graphite matrix. Silicon-graphite (SiG) composites combine the advantageous properties of graphite, i.e., large electrical conductivity and high structural stability, with the advantageous properties of silicon, i.e., high theoretical capacity. Graphite has a much lower volume expansion upon lithiation (≈ 10%) than pure silicon (≈ 300%) and provides a mechanically stable matrix. Herein, we present an investigation into the electrochemical performance and thickness change behavior of porous SiG anode compositions with silicon contents ranging from 0 wt% to 20 wt%. The electrode composites were studied using two methods: in situ dilatometry for the thickness change investigation and conventional coin cells for the assessment of electrochemical performance. The measurements show that the initial thickness change of SiG electrodes increased significantly with the silicon content, but it leveled off during…

The dispersing solvent used for fuel cell catalyst ink preparation plays a vital role in establishing the resulting morphology of the electrode layers, which in turn will impact the performance of proton exchange membrane (PEM) fuel cells. In this study, we report the impact of various ionomer dispersion solvents on PEM fuel cell performance and durability; two aqueous (1-propanol/water and 2-propanol/water) and several non-aqueous dispersing solvents (ethylene glycol and 1,2-butanediol) are compared. The cathode catalyst layer (CCL) fabricated using inks prepared with 1-propanol/water (3:1, w/w) exhibited the best initial performance followed by the CCL prepared using ethylene glycol. The CCLs made from non-aqueous ethylene glycol and 1,2-butanediol exhibited the best durability upon accelerated stress testing. Scanning transmission electron microscopy combined with energy dispersive X-ray spectroscopy indicated that, after the stress test, the distribution of both the Nafion ionomer and Pt nanoparticles within the CCLs prepared with non-aqueous ionomer dispersions underwent less…

Virtually all types of electrodes used in lithium-ion batteries expand and contract during cycling, which poses an engineering and design challenge. Information provided by X-ray diffraction (XRD) about alterations in the crystal structure of active materials may be insufficient to inform these engineering tasks. This is because it is unclear how these evolutions of the crystal structure translate into the measurable thickness changes at the electrode or cell level. In this study we investigate the thickness changes of electrodes during cycling using a dilatometry setup and compare them to XRD-measured crystal structure changes from scientific literature. Both the reliability of the dilation measurement and the electrochemical performance of the dilatometry setup are thoroughly validated and significantly exceed those of related studies that have been published in recent years. Various laboratory-made graphites as well as LiNi1/3Co1/3Mn1/3O2 (NMC111), LiNi0.6Co0.2Mn0.2O2 (NMC622), LiNi0.8Co0.1Mn0.1O2 (NMC811) and LiNi0.8Co0.15Al0.05O2 (NCA) electrodes and the positive electrode from…

Two of the main factors influencing the performance of Li-ion battery (LIB) electrodes are the kinetic losses due to the charge transfer resistance of the active material ( R ct ) and the ionic transport resistance in the electrolyte phase within the electrode pores ( R ion ). Seeking to increase the energy density of LIBs, ever higher active material loadings are applied, resulting in thicker electrodes for which R ion becomes dominant. As electrochemical impedance spectroscopy is commonly used to quantify R ct of electrodes, understanding the impact of R ion on the impedance response of thick electrodes is crucial. By use of a simplified transmission line model (TLM), we simulate the impedance response of electrodes as a function of electrode loading. This will be compared to the impedance of graphite anodes (obtained using a micro-reference electrode), demonstrating that their impedance response varies from purely kinetically limited at 0.6 mAh cm −2 to purely transport limited at 7.5 mAh cm −2 . We then introduce a simple method with which R ct and R ion can be determined from…

Li-ion batteries are being widely used in planetary missions, based on their impressive performance characteristics, including high specific energy, long life, and the ability to operate over a wide temperature range. Custom large-format Li-ion cells were used in the early planetary missions, e.g., Mars Rovers, Mars Landers, and Mars and Jupiter Orbiters. At the same time, several other robotic missions have utilized and are planning to utilize commercial 18650 lithium-ion cells, e.g., Mars Express, Lunar Reconnaissance Orbiter, Europa Clipper, as well as human-rated astronaut Extra-Vehicular Activities. Interest in commercial 18650 lithium-ion cells for NASA missions has increased in recent years due to distinct advantages over custom large-format cells, including higher specific energy and energy density, enhanced safety and reliability, modularity and redundancy in the battery design, and simpler charge methodology. Multiple commercial 18650 cells are available which can provide a specific energy of ∼250 Wh∙kg−1(20%–50% over custom cells) and a power density of ∼2 kW∙kg−1.…

Lithium-ion batteries face low temperature performance issues, limiting the adoption of technologies ranging from electric vehicles to stationary grid storage. This problem is thought to be exacerbated by slow transport within the electrolyte, which in turn may be influenced by ion association, solvent viscosity, and cation transference number. How these factors collectively impact low temperature transport phenomena, however, remains poorly understood. Here we show using all-atom classical molecular dynamics (MD) simulations that the dominant factor influencing low temperature transport in LP57 (1 M LiPF 6 in 3:7 ethylene carbonate (EC)/ethyl methyl carbonate (EMC)) is solvent viscosity, rather than ion aggregation or cation transference number. We find that ion association decreases with decreasing temperature, while the cation transference number is positive and roughly independent of temperature. In an effort to improve low temperature performance, we introduce γ -butyrolactone (GBL) as a low viscosity co-solvent to explore two alternative formulations: 1 M LiPF 6 in 15:15:70…

Sulfide solid electrolytes (SEs) show promise for Li metal solid-state batteries due to their high ionic conductivities and relative ease of manufacturing. However, many sulfide SEs suffer from limited electrochemical stability against Li metal electrodes. In this work, we use a suite ofoperandoanalytical techniques to investigate the dynamics of solid electrolyte interphase (SEI) formation and the associated effects on Li plating. We contrast a sulfide SE that forms an electrically insulating SEI (Li6PS5Cl) with an SE that forms an SEI with electrically conducting phases present (Li10GeP2S12). Using anode-free cell configurations, where the Li/SE interface is formed against a current collector, we perform complimentaryoperandovideo microscopy andoperandoX-ray photoelectron spectroscopy (XPS) experiments. The combination of these techniques allows for the interpretation of electrochemical voltage traces during Li plating. The electrically insulating nature of the SEI in Li6PS5Cl facilitates Li metal nucleation and plating after the initial SEI formation. In contrast, in cells that…

Lithium-ion batteries (LiBs) are recognized as the most rapidly growing energy storage technology. To improve the energy and power density of LiBs, tremendous progress has been made in every battery component. In this review, we focus on the investigations of electrolyte and electrode designs aimed at understanding and enhancing ion transport properties to improve the performance of LiBs. Theoretical, computational, and experimental studies of the importance of transport properties are highlighted, and the efforts to enhance the lithium transference number in organic electrolytes is discussed. We also review the significant ion transport challenges in porous electrodes and the demonstrated examples of advanced, high power/energy density electrodes. Overall, we focus on the most recent and pioneering works in terms of complex electrolytes with high transport properties and thick porous electrodes for high performance LiBs. This review intends to provide guidance for development of advanced electrolytes and electrodes for high performance LiBs through comprehensive compilation of…

Achieving high power performance and durability with low Pt loadings are critical challenges for proton exchange membrane fuel cells. PtCo catalysts developed on new carbon black supports show promise by simultaneously providing good oxygen reduction kinetics and local oxygen transport. We investigate the role of nanoscale morphology in the performance of these catalysts supported on accessible (HSC-e and HSC-f) and conventional (Ketjen Black) porous carbons using 3D electron tomography, nitrogen sorption, and electrochemical performance measurements. We find that the accessible porous carbons have hollow interiors with mesopores that are larger and more numerous than conventional porous carbons. However, mesopore-sized openings (>2 nm width) are too rare to account for significant oxygen transport. Instead we propose the primary oxygen transport pathway into the interior is through 1–2 nm microporous channels permeating the carbon. The increased mesoporosity in the accessible porous carbons results in a shorter diffusion pathlength through constrictive, tortuous micropores in the…

Heavy metal ions, which have harmful effects on living organisms, are extremely toxic to the environment. Therefore, with quick response time and low cost analytical instrument, it is of immense demand to assess the toxic levels of heavy metal ions. A promising and systematic way of perceiving the selective determination of metal ions in polluted water is electrochemical detection. Recent developments in metal organic frameworks (MOF) have ignited a considerable interest in the metal ion sensor field as an interesting class of electrode material. This paper reviews the MOF-based material as an electrode detection platform for toxic heavy metal ions. The rapidly evolving MOF has a 3D structure with tunable pore sizes, and a high specific area containing a large number of ions makes it ideal for ion exchange capture of toxic metal ions. The toxicity levels in the atmosphere of heavy metal ions such as arsenic, lead, mercury and cadmium and recent advances in the use of MOF as an active electrode material for estimating these metal ions are discussed. The key advantages and…

Various modeling techniques are used to predict the capacity fade of Li-ion batteries. Algebraic reduced-order models, which are inherently interpretable and computationally fast, are ideal for use in battery controllers, technoeconomic models, and multi-objective optimizations. For Li-ion batteries with graphite anodes, solid-electrolyte-interphase (SEI) growth on the graphite surface dominates fade. This fade is often modeled using physically informed equations, such as square-root of time for predicting solvent-diffusion limited SEI growth, and Arrhenius and Tafel-like equations predicting the temperature and state-of-charge rate dependencies. In some cases, completely empirical relationships are proposed. However, statistical validation is rarely conducted to evaluate model optimality, and only a handful of possible models are usually investigated. This article demonstrates a novel procedure for automatically identifying reduced-order degradation models from millions of algorithmically generated equations via bi-level optimization and symbolic regression. Identified models are…

Many electrochemical energy-conversion systems are evaluated by polarization curves, which report the cell voltage across a range of current densities and are a global measure of operation and state of health. Mathematical models can be used to deconstruct the measured overall voltage and identify and quantify the voltage-loss sources, such as kinetic, ohmic, and mass-transport effects. These results elucidate the best pathways for improved performance. In this work, we discuss several voltage-breakdown methods and provide examples across different low-temperature, membrane-based electrochemical systems including electrolyzers, fuel cells, and related electrochemical energy-conversion devices. We present best practices to guide experimentalists and theorists in polarization-curve breakdown analysis.

A novel Co 9 S 8 nanocage was fabricated via a metalorganic frameworks engaged strategy. The morphology and structure of the resulting Co 9 S 8 nanocage were carefully confirmed by scanning electron microscopy, powder X-ray diffraction, transmission electron microscope, and X-ray photoelectron spectroscopy. Then the as-synthesized Co 9 S 8 nanocage material was immobilized on a glassy carbon electrode (GCE) and served as an efficient sensing platform for determination of luteolin. Under optimized conditions, the prepared Co 9 S 8 /GCE shows significant electrocatalytic activity toward the oxidation of luteolin. By comparison with GCE and CoS/GCE, the proposed Co 9 S 8 /GCE results in great improvement in the electrochemical response of luteolin. Meanwhile, the Co 9 S 8 based-sensor presents an excellent linear relationship with the concentration of luteolin ranging from 0.01 to 20 μ M. Then, the limit of detection based on S/N = 3 was estimated to be 0.8 nM. In addition, the Co 9 S 8 /GCE displays good repeatability, reproducibility, and selectivity. Finally, the simplicity and low…

Gas sensors have become an integral part of the industrial and domestic sector, due to the increased emissions from industries, automobiles, and thereby exposure of the harmful gases like CO, NO 2 , SO 2 , CO 2 , NH 3 etc. Metal oxide-semiconducting (MOS) chemiresistive gas sensors are the most popular commercial gas sensors available in the market. However, they need high operational temperature for activation and deactivation, which is a serious concern for sensitive combustible environments, as well as in other applications where flexibility, low power consumption, and miniaturization are desirable. Hence, gas sensors those exhibit high sensitivity and selectivity to the target gases, at room temperature are the need-of-hour in the market. This review focuses on various strategies and approaches those being employed and the challenges ahead to realize such room temperature chemiresistive gas sensing; viz: (i) 1 D-nanostructuring of various conventional metals and metal oxides ; (ii) Nano +heterojunctions between metal oxide-metal oxides and noble metals ; (iii) 2 D-materials ;…

Layered Ni-rich transition metal oxides like so-called NCMs are one of the most-promising high-energy density cathode active materials (CAMs) for next-generation Li-Ion batteries. However, compared to NCMs with low nickel content, Ni-rich NCMs suffer from a highly reactive surface that leads to an accumulation of surface contaminants and also from a higher soluble base content. Since a detailed understanding of the formation rate of surface contaminants is still lacking, we will investigate the effect of extended storage in high relative humidity air of a Ni-rich NCM851005 (Li 1+ δ (Ni 0.85 Co 0.10 Mn 0.05 ) 1- δ O 2 , with δ typically ∼0.005–0.03) and a low nickel content NCM111 (Li 1+ δ (Ni 1/3 Co 1/3 Mn 1/3 ) 1- δ O 2 ) on the build-up of surface contaminants. The formation rate of the surface contaminants during this accelerated wet-storage test is quantified by TGA-MS under Ar. To elucidate the processes occurring during the TGA-MS experiments, as-received and wet-stored CAMs are introduced into an XPS chamber where they are heated in situ to different temperatures, followed by…

Hydrogen crossover poses a crucial issue for polymer electrolyte membrane (PEM) water electrolysers in terms of safe operation and efficiency losses, especially at increased hydrogen pressures. Besides the impact of external operating conditions, the structural properties of the materials also influence the mass transport within the cell. In this study, we provide an analysis of the effect of elevated cathode pressures (up to 15 bar) in addition to increased compression of the membrane electrode assembly on hydrogen crossover and the cell performance, using thin Nafion 212 membranes and current densities up to 3.6 A cm −2 . It is shown that a higher compression leads to increased mass transport overpotentials, although the overall cell performance is improved due to the decreased ohmic losses. The mass transport limitations also become visible in enhanced anodic hydrogen contents with increasing compression at high current densities. Moreover, increases in cathode pressure are amplifying the compression effect on hydrogen crossover and mass transport losses. The results indicate…

Polymer-electrolyte membranes (PEMs) are a key component in electrochemical energy conversion devices where their main function is to selectively transport ionic species. Reducing PEM thickness is an effective strategy for improving performance by minimizing transport losses. However, how thickness affects the intrinsic properties of a membrane remains unexplored. This work aims to understand the effect of membrane thickness on structure-property relationships of 3 M perfluorosulfonic acid (PFSA) ionomer. We carried out a systematic investigation of membranes in a thickness range of 5–70 μ m to examine their hydration behavior, morphology, crystallinity, mechanical properties, and gas and proton transport, with a discussion on the effect of thermal treatments. The collected dataset demonstrates PFSA membranes exhibit transitions in certain structural features below 10 μ m, accompanied by an increased anisotropy in swelling and conductivity. Many properties deviate within 10%–20% without monotonic changes with thickness, however, linear correlations are observed between thickness and…

Water-in-salt electrolytes (WiSEs) are a class of super-concentrated electrolytes that have shown much promise in replacing organic electrolytes in lithium-ion batteries. At the extremely high salt concentrations of WiSEs, ionic association is more complicated than the simple ion pair description. In fact, large branched clusters can be present in WiSEs, and past a critical salt concentration, an infinite percolating ionic network can form spontaneously. In this work, we simplify our recently developed thermodynamic model of reversible ionic aggregation and gelation, tailoring it specifically for WiSEs. Our simplified theory only has a handful of parameters, all of which can be readily determined from simulations. Our model is able to quantitatively reproduce the populations of ionic clusters of different sizes as a function of salt concentration, the critical salt concentration for ionic gelation, and the fraction of ions incorporated into the ionic gel, as observed from molecular simulations of three different lithium-based WiSEs. The extent of ionic association and gelation…

The venting of hot gases due to rupture of a Li-ion cell during thermal runaway may rapidly transfer thermal energy to neighboring cells in a battery pack and cause propagation of thermal runaway. While thermal runaway has been studied extensively through both measurements and simulations, there is a relative lack of research on the impact of the venting process on thermal runaway propagation. This work presents a non-linear thermal-fluidic simulation of supersonic turbulent flow of hot gases ejecting from a trigger cell and spreading to neighboring cells. Assuming isentropic flow, temperature and speed of the gas flow as functions of time are estimated based on past measurements. These data are used in simulations to determine the thermal impact of the venting process on neighboring cells. The impact of various geometrical parameters of the battery pack on the spreading of venting gases is investigated. Results indicate that cell-to-cell gap, overhead gap and the location of the vent hole on the cell body strongly influence the nature of propagation of thermal runaway to…

The durability of carbon supported PtCo-alloy based nanoparticle catalysts play a key role in the longevity of proton-exchange membrane fuel cells (PEMFC) in electric vehicle applications. To improve its durability, it is important to understand and mitigate the various factors that cause PtCo-based cathode catalyst layers (CCL) to lose performance over time. These factors include i) electrochemical surface area (ECSA) loss, ii) specific activity loss, iii) H+/O2-transport changes and iv) Co2+contamination effects. We use a catalyst-specific accelerated stress test (AST) voltage cycling protocol to compare the durability of Pt and PtCo catalysts at similar average nanoparticle size and distribution. Our studies indicate that while Pt and PtCo nanoparticle catalysts suffer from similar magnitudes of electrochemical surface area (ECSA) losses, PtCo catalyst shows a significantly larger cell voltage loss at high current densities upon durability testing. The distinctive factor causing the large cell voltage loss of PtCo catalyst appears to be the secondary effects of the leached…

This work uses accelerating rate calorimetry to evaluate the impact of cell chemistry, state of charge, cell capacity, and ultimately cell energy density on the total energy release and peak heating rates observed during thermal runaway of Li-ion batteries. While the traditional focus has been using calorimetry to compare different chemistries in cells of similar sizes, this work seeks to better understand how applicable small cell data is to understand the thermal runaway behavior of large cells as well as determine if thermal runaway behaviors can be more generally tied to aspects of lithium-ion cells such as total stored energy and specific energy. We have found a strong linear correlation between the total enthalpy of the thermal runaway process and the stored energy of the cell, apparently independent of cell size and state of charge. We have also shown that peak heating rates and peak temperatures reached during thermal runaway events are more closely tied to specific energy, increasing exponentially in the case of peak heating rates.

A lithium- and manganese-rich layered transition metal oxide (LMR-NCM) cathode active material (CAM) is processed on a pilot production line and assembled with graphite anodes to ≈7 Ah multilayer pouch cells. Each production step is outlined in detail and compared to NCA/graphite reference cells. Using laboratory coin cell data for different CAM loadings and cathode porosities, a simple calculation tool to extrapolate and optimize the energy density of multilayer pouch cells is presented and validated. Scanning electron microscopy and mercury porosimetry measurements of the cathodes elucidate the effect of the CAM morphology on the calendering process and explain the difficulty of achieving commonly used cathode porosities with LMR-NCM cathodes. Since LMR-NCMs exhibit strong gassing during the first cycles, a modified formation procedure based on on-line electrochemical mass spectroscopy is developed that allows stable cycling of LMR-NCM in multilayer pouch cells. After formation and degassing, LMR-NCM/graphite pouch cells have a 30% higher CAM-specific capacity and a ≈5%–10% higher…

Lithium ion battery thermal runaway constitutes a severe inhibitor for the spread and application of electric vehicles and widespread adoption of renewable energy. Reliable and early warning of thermal runaway calls for a technique capable of detecting abnormal response well in advance of the critical event and being effective to the module when a single cell in it has safety issues. In this study, electrochemical impedance spectrum (EIS) dependence on cell temperature and deformation is exploited to generate a two-staged warning method with three indicators in three frequency ranges. Specifically, the first stage utilizes the high sensitivity of EIS at the intermediate-frequency range to abnormal cell internal temperature rise, which is before self-heating temperature, as an early indicator for safety issues. The second stage utilizes the abrupt changes in EIS behaviors due to cell deformation in high- and low-frequency ranges, which are more sensitive than cell voltage change, as indicators for the thermal runaway onset temperature. The potential and issues of such an EIS-based…

WO 3 -based gas sensors have attracted the attention of researchers around the world in creating and developing sensors that are sensitive, stable, and have excellent reproducibility against harmful gases. Various studies that have been performed since the last few years exhibited the superior potential of WO 3 in carrying out optimal chemisorption of oxidizing and reducing gas molecules. The additional materials such as metal, metal oxide, and carbon nanomaterial can significantly widen the active state area of the WO 3 surface and other facts in various studies illustrate that the addition of polymers will change the characteristics of the semiconductor sensor. This review provides a comprehensive review of the development and modification of WO 3 for enhancing toxic gas sensor performances. In addition, the discussion of the sensing mechanism, future opportunities as well as challenges will be addressed thereby can inspire research progress on WO 3 -based toxic gas detection sensors.

Lithium-ion batteries operate predominantly at room temperature, but some applications such as electric vehicles also demand operation at higher temperature. This is especially challenging for cathode active materials (CAMs), which undergo an accelerated failure at elevated temperature. Here, we systematically compare the capacity fading of the Ni-rich NCM-811 at two different temperatures. The first dataset over 1000 cycles at 22 °C stems from a former study, while the NCM-811/graphite full-cells are investigated now under similar conditions at 45 °C for 700 cycles. We focus on the CAM by using pre-lithiated graphite anodes. The capacity loss due to NCM-811 degradation at 45 °C is more than doubled compared to 22 °C. The underlying mechanisms related to the bulk and the surface of the CAM are quantified by several ex situ techniques such as X-ray powder diffraction, half-cell cycling with impedance spectroscopy, and Kr-BET. The aging happens mainly at the surface of the primary particles, forming a resistive, disordered surface layer, whose thickness is estimated to reach ≈6 nm at…

Data-driven methods for battery lifetime prediction are attracting increasing attention for applications in which the degradation mechanisms are poorly understood and suitable training sets are available. However, while advanced machine learning and deep learning methods promise high performance with minimal data preprocessing, simpler linear models with engineered features often achieve comparable performance, especially for small training sets, while also providing physical and statistical interpretability. In this work, we use a previously published dataset to develop simple, accurate, and interpretable data-driven models for battery lifetime prediction. We first present the “capacity matrix” concept as a compact representation of battery electrochemical cycling data, along with a series of feature representations. We then create a number of univariate and multivariate models, many of which achieve comparable performance to the highest-performing models previously published for this dataset; thus, our work can serve as a comprehensive benchmarking study for this dataset. These…

A typical flow field plate of proton exchange membrane fuel cells has a distribution zone that connects the input ports and main channel region where major reactions take place. In this study, the effects of two distribution zone designs, i.e., the channel-ridge distribution zone (CRDZ) and dot matrix distribution zone (DMDZ), on the gas distribution uniformity and pressure drop are investigated numerically. For the flow fields with CRDZ, the theoretical mass flow rates and pressure distributions are found to agree with numerical results well. The flow rate distributions in the flow fields become more uniform when the turning angle increases to special angle. To design the flow fields with CRDZ, the channels can be arranged with simple geometry lines in the first step and then optimised with CFD considering the actual size to achieve a more uniform distribution and suitable pressure drop. For the flow fields with DMDZ, the uniformity of gas distribution depends on the shunt and dispersion effects of dot matrix, and the rectification and expansion effects of the distribution chamber.…

Lithium-ion batteries can experience mechanical loads for a variety of reasons, including the rigidity of the cell casing itself, bracing of cell stacks in a module, which is generally due to limited space in the place of installation, or as a result of accidents or abuse. In all of these cases, and exacerbated by faulty manufacturing or assembly, the mechanical loads may be non-uniform across the cell surface. Here , we present an analysis of the effects of such non-uniform mechanical loads on the current density distribution during charging and show that they can provoke localized lithium plating. Pressure-compression relationships of individual cell components were determined experimentally and implemented into a pseudo-3D axisymmetric electrochemical-mechanical cell model of a 2.1 Ah pouch cell by Kokam, South Korea. The modeling results were successfully validated by comparison to a post-mortem evaluation of pouch cells that were cycled while being locally compressed.

Following the demand for increased energy density of lithium-ion batteries, the Ni content of the Nickel-Cobalt-Manganese oxide (NCM) cathode materials has been increased into the direction of LiNiO 2 (LNO), which regained the attention of both industry and academia.To understand the correlations between physicochemical parameters and electrochemical performance of LNO, a calcination study was performed with variation of precursor secondary particle size, maximum calcination temperature and Li stoichiometry.The structural properties of the materials were analyzed by means of powder X-ray diffraction, magnetization measurements and half-cell voltage profiles.All three techniques yield good agreement concerning the quantification of Ni excess in the Li layer (1.6%-3.7%).This study reveals that the number of Li equivalents per Ni is the determining factor concerning the final stoichiometry rather than the calcination temperature within the used calcination parameter space.Contrary to widespread belief, the Ni excess shows no correlation to the 1 st cycle capacity loss, which indicates…

X-ray Photoelectron Spectroscopy and Time-of-Flight Secondary Ion Mass Spectrometry were combined to characterize the surface oxides (native oxides and passive films) formed on Ni-based alloys containing chromium and molybdenum. Two alloys were studied, Ni-20Cr and Ni-20Cr-10Mo (in wt.%). For Ni-20Cr, both native oxide and passive films formed in acidic medium present a duplex structure comprising a Ni and Cr outer hydroxide layer and a Cr inner oxide layer. The Ni-20Cr-10Mo alloy presents a similar bilayer structure, but with Mo oxide located at the outer layer/inner layer interface. Cr enrichment is observed after passivation for both alloys. The corrosion resistance in acidic solution containing chlorides is enhanced by Mo, and by electrochemical pre-passivation in Cl free solution.

Green hydrogen produced through anion exchange membrane water electrolysis is a promising, low-cost chemical storage solution for intermittent renewable energy sources. Low-temperature electrolysis using anion exchange membranes (AEM) combines the benefits of established water electrolysis technologies based on alkaline electrolysis and proton exchange membrane electrolysis. The anion conductive ionomers (ACI) used in the AEM electrolyzer (AEMEL) electrodes has been investigated. The ACI serves two primary purposes: (i) facilitate hydroxide conduction between the catalyst and bulk electrolyte and (ii) bind the catalyst to the porous transport layer and membrane. High ion exchange capacity (IEC) ACIs are desired, however, high IEC can cause excessive water uptake (WU) and detrimental ACI swelling. Proper water management is a key factor in obtaining maximum performance in AEM-based devices. In this study, a series of poly(norbornene)-based ACIs were synthesized and deployed in hydrogen evolving AEMEL cathode electrodes. A balance between ionic conductivity, WU and ionomer swelling…

Ni-rich cathode materials suffer from poor capacity retention due to micro-cracking and interfacial reactivity with electrolyte. Addition of tungsten (W) to some Ni-rich materials can improve capacity retention. Here, a WO3 surface coating is applied on Ni-rich hydroxide precursors before heating with lithium hydroxide. After heating in oxygen, Ni-rich materials with any of the commonly used dopants (magnesium, aluminum, manganese, etc.) show a “universal” improvement in capacity retention. Experimental characterization and theoretical modelling showed W was concentrated in the grain boundaries between the primary grains of secondary particles of the layered oxides, and W is incorporated in amorphous LixWyOz phases rather than as a substituent in the LiNiO2 lattice. This self-infusion of W in the grain boundaries during synthesis also significantly restricts primary crystallite grain growth. Along with smaller primary grain size, the LixWyOz phases in the grain boundaries lead to improved resistance to microcracking and reduced surface or interfacial reactivity. Improving the…