The 50 most-cited articles in Journal of The Electrochemical Society, 2023

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…

Improving utilization, performance, and stability of low iridium (Ir)-loaded anodes is a key goal to enable widespread adoption of polymer electrolyte membrane water electrolysis (PEMWE) for clean hydrogen production. A potential limitation is high ionic or electronic resistance of the anode catalyst layer, which leads to poor catalyst utilization, increased voltage losses, and high local overpotentials that can accelerate degradation. While catalyst layer resistance is relatively well-understood in fuel cells and other porous electrode systems, characterization of these effects is not as well established in PEMWE research. Here we present in-situ methods for measuring catalyst layer resistance in electrolysis cells using a non-faradaic H 2 /H 2 O condition as well as methods for calculating the associated voltage losses. These methods are applied to anode catalyst layers based on IrO 2 nanoparticles as well as dispersed nano-structured thin film (NSTF) Ir catalysts. Trends with anode catalyst loading and interactions between the porous transport layer and catalyst layer are…

One of the most challenging tasks of modern battery management systems is the accurate state of health estimation. While physico-chemical models are accurate, they have high computational cost. Neural networks lack physical interpretability but are efficient. Physics-informed neural networks tackle the aforementioned shortcomings by combining the efficiency of neural networks with the accuracy of physico-chemical models. A physics-informed neural network is developed and evaluated against three different datasets: A pseudo-two-dimensional Newman model generates data at various state of health points. This dataset is fused with experimental data from laboratory measurements and vehicle field data to train a neural network in which it exploits correlation from internal modeled states to the measurable state of health. The resulting physics-informed neural network performs best with the synthetic dataset and achieves a root mean squared error below 2% at estimating the state of health. The root mean squared error stays within 3% for laboratory test data, with the lowest error observed…

Electrochemical impedance spectroscopy (EIS) is used widely in electrochemistry. Obtaining EIS data is simple with modern electrochemical workstations. Yet, analyzing EIS spectra is still a considerable quandary. The distribution of relaxation times (DRT) has emerged as a solution to this challenge. However, DRT deconvolution underlies an ill-posed optimization problem, often solved by ridge regression, whose accuracy strongly depends on the regularization level λ . This article studies the selection of λ using several cross-validation (CV) methods and the L-curve approach. A hierarchical Bayesian DRT (hyper- λ ) deconvolution method is also analyzed, whereby λ 0 , a parameter analogous to λ , is obtained through CV. The analysis of a synthetic dataset suggests that the values of λ selected by generalized and modified generalized CV are the most accurate among those studied. Furthermore, the analysis of synthetic EIS spectra indicates that the hyper- λ approach outperforms optimal ridge regression. Due to its broad scope, this research will foster additional research on the vital…

The corrosion characteristics of passive films on 1060, 2024 and 5083 aluminum alloys formed in citric acid solution are studied in Cl–-containing solutions by combining scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The passive film on 1060 pure Al exhibits the best corrosion resistance while the presence of alloying elements (Cu and Mg) in the passive films reduce the corrosion resistance of the passive films on 2024 and 5083 Al alloys. According to first-principles calculations, Cu/Mg doping γ-Al2O3 surfaces are looser and more reactive than pure γ-Al2O3 (110) surface, and Cl adsorption behavior is changed in Cu/Mg doping γ-Al2O3 surfaces. This illuminates the difference of corrosion resistances of 1060, 2024 and 5083 aluminum alloys from the aspects of the passive film structure and interaction of chlorine ions with the passive films.

Electrolytes play a critical role in enabling the stable cycling of rechargeable lithium (Li) metal batteries. While carbonate-based and ether-based electrolytes are widely investigated respectively with notably improved electrochemical performances in Li metal batteries, few works have been conducted for systematical understanding and comparison of these two systems. Here, we side-by-side investigated carbonate-based (dimethyl carbonate, DMC) and ether-based (1,2-dimethoxyethane, DME) electrolyte systems in terms of cathodic chemical/electrochemical stabilities, anodic stability, transport properties, Li morphology, Coulombic efficiency, and full cell performances. The experimental results indicate that ether-based electrolyte systems exhibit all-around superior compatibilities with Li metal anode, although the carbonate-based systems can be significantly improved from the commercial baseline by introducing fluorinated co-solvent. The ether-based systems, even at low concentrations, demonstrate acceptable anodic stability when charged to a reasonable cut-off voltage in practical…

This study investigates the cycling performance and failure mechanisms of sodium-ion pouch cells with layered NaCa 0.03 [Mn 0.39 Fe 0.31 Ni 0.22 Zn 0.08 ]O 2 positive electrodes and hard carbon negative electrodes. Charge/discharge cycling between different lower and upper cut-off voltages at C/5 and 40 °C showed better capacity retention, lower voltage polarization, and less gassing when the upper cut-off voltage was limited to 3.80 V. Electrodes harvested from pouch cells after cycling were reassembled in symmetric coin cells to reveal the origin of voltage polarization by electrochemical impedance spectroscopy. The negative electrode charge transfer resistance dominated the full cell impedance and increased considerably after 100 cycles at 40 °C with standard alkyl carbonate electrolyte. The positive electrode impedance was less significant but increased dramatically when the full cell voltage was 4.00 V. Furthermore, ultra-high precision coulometry used for the in situ detection of sodium plating at 40 °C, revealed significant plating at charging rates greater C/2. Based on this…

The porous transport layer (PTL)/catalyst layer (CL) interface plays a crucial role in the achievement of high performance and efficiency in polymer electrolyte membrane water electrolyzers (PEMWEs). This study investigated the effects of the PTL/CL interface on the degradation of membrane electrode assemblies (MEAs) during a 4000 h test, comparing the MEAs assembled with uncoated and Ir-coated Ti PTLs. Our results show that compared to an uncoated PTL/CL interface, an optimized interface formed when using a platinum group metal (PGM) coating, i.e., an iridium layer at the PTL/CL interface, and reduced the degradation of the MEA. The agglomeration and formation of voids and cracks could be found for both MEAs after the long-term test, but the incorporation of an Ir coating on the PTL did not affect the morphology change or oxidation of IrO x in the catalyst layer. In addition, our studies suggest that the ionomer loss and restructuring of the anodic MEA can also be reduced by Ir coating of the PTL/CL interface. Optimization of the PTL/CL interface improves the performance and…

In this work we investigate the effect of platinum loading and layer thickness on cathode catalyst degradation by a comprehensive in situ and STEM-EDS characterization. To decouple the effect of the platinum loading and layer thickness from each other, the experiments were categorized in two sets, each with cathode loadings varying between 0.1 and 0.4 mg Pt cm −2 : (i) Samples with a constant Pt/C ratio and thus varying layer thickness, and (ii) samples with varying Pt/C ratios, achieved by dilution with bare carbon, to maintain a constant layer thickness at different platinum loadings. Every MEA was subjected to an accelerated stress test, where the cell was operated for 45,000 cycles between 0.6 and 0.95 V. Regardless of the Pt/C ratio, a higher relative loss in electrochemically active surface area was measured for lower Pt loadings. STEM-EDS measurements showed that Pt was mainly lost close to the cathode—membrane interface by the concentration driven Pt 2+ ion flux into the membrane. The size of this Pt-depletion zone has shown to be independent on the overall Pt loading and…

We assess the suitability of potassium ferri-/ferrocyanide as an electroactive species for long-term utilization in aqueous organic redox flow batteries. A series of electrochemical and chemical characterization experiments was performed to distinguish between structural decomposition and apparent capacity fade of ferri-/ferrocyanide solutions used in the capacity-limiting side of a flow battery. Our results indicate that, in contrast with previous reports, no structural decomposition of ferri-/ferrocyanide occurs at tested pH values as high as 14 in the dark or in diffuse indoor light. Instead, an apparent capacity fade takes place due to a chemical reduction of ferricyanide to ferrocyanide, via chemical oxygen evolution reaction. We find that this parasitic process can be further exacerbated by carbon electrodes, with apparent capacity fade rates at pH 14 increasing with an increased ratio of carbon electrode surface area to ferricyanide in solution. Based on these results, we report a set of operating conditions that enables the long-duration cycling of alkaline…

Electrochemical migration (ECM) is one of the serious failure modes encountered in electronic devices due to the electrochemical reactions triggered by the presence of moisture and bias voltage, leading to the growth of dendrites and short circuits. The classical ECM mechanism consists of four consecutive stages: (i) electrolyte formation, (ii) anodic dissolution, (iii) ion transport, and (iv) dendrite growth. ECM is a delicate process that involves a combination of a good number of factors, such as the electrode properties, climatic conditions, contaminants, electric field, additives, etc. We intend to provide a comprehensive review of the complex effects that these factors have on each stage of ECM and provide insights into the recent developments in ECM research. Previous findings, current debates and recent discoveries are covered in this article. This review paper also provides a review of recent strategies for ameliorating ECM failures in electronics.

A long-term test of 2000 h has been carried out on a typical solid oxide cell in electrolysis mode at −1 A.cm −2 and 750 °C. The 3D reconstructions of the pristine and aged cermet have revealed a strong Ni depletion at the electrolyte interface. To explain this result, an electrochemical and phase-field model has been developed to simulate the Ni migration in Ni/YSZ electrode. For this purpose, a mechanism has been proposed that takes into account the impact of polarization on the Ni/YSZ wettability. In this approach, it assumes that the Ni/YSZ interfacial energy is changed by the concentration of oxygen vacancies in the electrochemical double layer. Thanks to the model, the Ni migration has been computed in the same condition than the experiment and complemented by a simulation in reverse condition in SOFC mode. In good agreement with the experiment, the simulations have revealed a strong Ni depletion at the electrolyte interface after operation under electrolysis current. On the contrary, a negligible Ni redistribution with a very slight Ni enrichment has been predicted at the…

The composition of layered transition metal oxides (LiMO2, M = Ni, Co, Mn) as cathode active materials (CAMs) is currently trending towards higher nickel contents, which can provide more capacity and energy. The origin of this performance improvement is often ascribed to the lower potential of nickel-rich CAMs, suppressing detrimental electrochemical electrolyte oxidation. In this study, it is shown that the stability limit of LiMO2-based CAMs is not determined by the stability window of typical electrolytes in terms of potential but by the CAM composition, governing the structural stability at high degrees of delithiation. The latter is investigated for five CAMs with distinct composition (LCO, NCM111, NCM622, NCM851005, and LNO) as a function of upper cutoff potential and thus state of charge (SOC). Short-term cycling experiments with an increasing upper cutoff potential as well as extended cycling to selected SOCs reveal stability limits between 66 and 86 %SOC depending on the CAM composition. On-line electrochemical mass spectrometry (OEMS) does not only allow to exclude any…

In this study, we employed a zeolite imidazolate framework (ZIF-67) modified glassy carbon electrode (GCE) as a platform for the electrochemical detection of epinephrine. The ZIF-67 modified glassy carbon electrode (GCE) exhibited excellent electrocatalytic activity towards the detection of epinephrine in phosphate buffer (PBS, pH 7.0). The proposed ZIF-67 displayed superior electrocatalytic activity towards the oxidation of epinephrine in the 0.5−50 μ M linear range with a limit of detection (LOD) of 2.1 μ M, and a sensitivity of 0.06 μ A μ M −1 cm −2 . The efficacy of the proposed biosensor was demonstrated for the direct determination of epinephrine from serum and urine samples. All these results confirmed the usefulness of ZIF-67 modified electrodes for clinical analysis.

The expression for the exchange current density to describe the intercalation kinetics of Li-ion battery materials proposed by Newman and coworkers has been used extensively for battery modeling, however its applicability to existing battery materials should be validated. Here we show an electrochemical impedance spectroscopy (EIS) analysis of the kinetic behavior of NCM 111 as a function of electrolyte salt concentration and state-of-charge (SOC) and compare it to the proposed theory. An areal capacity dependent EIS analysis first gives insights into the feasibility of measuring kinetic and transport parameters, including the solid diffusion resistance of lithium, showing that low-areal capacity electrodes are required to predominantly probe the kinetics. We then show how the charge transfer kinetics follow a Butler-Volmer type concentration dependent behavior for lower concentrated electrolytes (≤1.5 M) but deviate from the proposed theory at higher salt concentrations. A further SOC dependent analysis shows how NCM 111 generally follows the proposed theory of U-shaped symmetric…

The effect of ionomer to carbon (I/C) weight ratio and relative humidity (RH) on cathode catalyst degradation was investigated by comprehensive in situ characterization. Membrane electrode assemblies (MEA) with I/C ratios of 0.5, 0.8 and 1.2 were subjected to an accelerated stress test performed at 40, 70 and 100% RH. The results show an increasing loss in electrochemical active surface area (ECSA) for both higher I/C ratios and RH during voltage cycling. To differentiate between ionomer and water connected ECSA, carbon monoxide stripping measurements were performed at varying RH. Before degradation, all MEAs show comparable total ECSA values, while higher I/C ratios lead to a larger fraction of ionomer connected ECSA. After degradation, ECSA measurements of the lowest I/C ratio showed a relatively higher loss of Pt in contact with ionomer than Pt in contact with water, while an opposite trend was observed for higher I/C ratios. H 2 /N 2 impedance measurements showed drastically increasing protonic catalyst layer resistances for decreasing RH especially at low I/C ratios, which…

In the “Li0-free” architecture, cells are manufactured with a bare anode current collector and the Li metal anode is plated in situ during the first charging step. While this architecture has many attractive qualities from manufacturing and energy density perspectives, stable Li plating in solid-state “Li0-free” cells can be challenging. It is generally accepted that the Li overpotential affects Li homogeneity in “Li0-free” cells. We demonstrate that the nucleation overpotential for Li plating in solid-state “Li0-free” cells using commercial current collectors can be eliminated by introducing metal clusters that guide Li nucleation. Au is used as model alloying metal cluster. Here, we demonstrate stable Li plating with thickness 16.5 μm (3.3 mAh cm−2) in oxide solid-state electrolyte “Li0-free” cells enabled by Au metal clusters. It is shown that 97% of the in situ plated Li can be reversibly stripped at 60 °C and 2.5 MPa. Conversely, Au interlayers which are flat and continuous instead of clustered in morphology consistently showed short-circuiting during in situ Li plating,…

In the present study, a stable and more selective electrochemical sensor for catechol (CC) detection at magnetic molecularly imprinted polymer modified with green reduced graphene oxide modified glassy carbon electrode (MIP/rGO@Fe 3 O 4 /GCE). Two steps have been applied to achieve the imprinting process: (1) adsorption of CC on the surface of the polypyrrole (Ppyr) during the polymerization of pyrrole and (2) the green extraction of the template (CC) from the mass produced. Hence, the present paper doesn’t present the first use of MIP technology for CC identification but, it presents a new extraction process. The MIP/rGO@Fe3O4/GCE was characterized by voltammetry techniques and exhibited a wide linear range from1 50 μ M of CC while the detection limits were estimated to be around 4.18 nM CC and limit of quantification in the range of 12.69 nM CC. Furthermore, the prepared MIP-based sensor provided outstanding electroanalytical performances including high selectivity, stability, repeatability, and reproducibility. For the accurate estimation of CC concentrations, an artificial…

Reliable experimental methods for measuring local potentials in lithium-ion battery cells are challenging but vital for a deep understanding of internal processes at the individual electrode level, and to parameterize and validate electrochemical models. Different three-electrode setups and reference electrodes (REs) have been developed in recent years. Some are based on custom laboratory setups or are small, e.g. coin cell sized. This work addresses internal potentials and half-cell impedances in the widely used single-layer pouch (SLP) cell format and proposes a novel multi-reference electrode cell design, enabling spatially resolved measurements. For the first time, it is shown how multiple 25 μm and 50 μm thin gold wire REs, together with a larger LTO-RE, can be used to study occurring inhomogeneities, considering the geometrical anode overhang. Special attention is given to the subtleties of the measurements and their interpretation. Multiple REs allow plausibility checks and confirm stability for both types during a continuous measurement period of more than 7,500 h (>10…

Developing green anticorrosive films is gaining great attention in science and engineering. Citrus fruit peels are mainly discarded as waste, although they can be an excellent repository of phytochemicals, that can be exploited as mitigating agents for corrosion. Herein, we report the high anticorrosion activity of a citrus extract for low-carbon steel in 1 M HCl solution at different temperatures. The main extract constituents were identified by MS and NMR. Two polymethoxyflavones (PMFs), namely nobiletin and heptamethoxyflavone, were identified as major constituents of the extract and the crude PMFs-based extract was investigated for corrosion protection. Using potentiodynamic polarization, weight loss and electrochemical impedance spectroscopy (EIS) methods, this extract revealed improved inhibition efficiency of 94%. The inhibition mechanism was elucidated by considering electrochemical kinetics and adsorption thermodynamics. SEM and UV–vis supported the electrochemical results. PMFs-based extract acted as a mixed-type inhibitor with a Langmuir model of adsorption. Importantly,…

Predicting changes in cell resistance and thickness as the battery ages can be as important as capacity fade in informing vehicle resale value, pack replacement schedules, and viability for repurposing before eventual recycling. Three well-known degradation mechanisms, namely SEI growth, lithium plating, and electrode particle fracture due to reversible expansion and contraction, are revisited and tuned using cycling data from cells experiencing plating and having significant loss of anode active material as the dominant degradation mechanism. Therefore, lifetime prediction achieved in this work cannot rely only on SEI growth rates calibrated from calendar aging test. More importantly, our model uses capacity-predictive irreversible SEI growth, net growth in plating, and accumulation of particle fracture as the cells cycle to predict the irreversible increases in cell thickness through a single set of tuned parameters. Last, but not least, the capacity-predictive degradation model can also predict the increased resistance through another single set of parameters. These two sets of…

Impedance and dielectric spectroscopies are closely related techniques for measuring the electrical properties of materials. The techniques differ in two ways. First, impedance measurements are usually made over several decades of frequency (i.e. broadband) whereas most dielectric measurements are made at fixed frequency. Second, time constants that control semicircles in impedance complex plane plots and peaks in permittivity or tan δ spectroscopic plots are not the same. Differences between the techniques are confined to data analysis procedures and interpretation since they use similar instrumentation for measurements and data collection. In impedance data, time constants represent conducting components and parallel resistance-capacitance (RC) combinations; in permittivity data, they represent dielectric processes and series RC combinations. Using broadband data, it is possible to (i) determine the best equivalent circuit to fit experimental data, (ii) unambiguously evaluate and assign resistance, capacitance, and time constant parameters to regions of the material being measured…

In this research a highly microporous Cu-BTC (denoted as HKUST-1) was synthesized using a simple and rapid synthesis room temperature method. The as-prepared HKUST-1 obtained at room temperature for 10 min exhibited a very high Brunauer–Emmett–Teller (BET) surface area of 1875 m2/g, pore volume (Vp) of 0.789 cm3/g, and average micropore size of 7.84 Å. Based on this product, we successfully fabricated a conductive electrochemical sensor HKUST-1@PANI by polymerizing a conductive polyaniline polymer (PANI) around the metal-organic framework HKUST-1. Fourier transform infrared (FTIR) spectra, X-ray diffraction pattern (XRD) support the formation of HKUST-1@PANI. Furthermore, scanning electron microscopy (SEM) studies confirmed that PANI uniformly covered the surface of HKUST-1. We used the resulting material to build a new electrochemical sensor for the reliable detection of lead ions. The electrochemical response of the developed sensor towards ions was evaluated using differential pulse voltammetry (DPV). Under optimized conditions, linear detection was reproducible over the Pb2+…

Analysis of Electrochemical Impedance Spectroscopy (EIS) data for electrochemical systems often consists of defining an Equivalent Circuit Model (ECM) using expert knowledge and then optimizing the model parameters to deconvolute various resistance, capacitive, inductive, or diffusion responses. For small data sets, this procedure can be conducted manually; however, it is not feasible to manually define a proper ECM for extensive data sets with a wide range of EIS responses. Automatic identification of an ECM would substantially accelerate the analysis of large sets of EIS data. We showcase machine learning methods to classify the ECMs of 9,300 impedance spectra provided by QuantumScape for the BatteryDEV hackathon. The best-performing approach is a gradient-boosted tree model utilizing a library to automatically generate features, followed by a random forest model using the raw spectral data. A convolutional neural network using boolean images of Nyquist representations is presented as an alternative, although it achieves a lower accuracy. We publish the data and open source the…

We present a quantitative bibliometric study of flow battery technology from the first zinc-bromine cells in the 1870’s to megawatt vanadium RFB installations in the 2020’s. We emphasize, that the cost advantage of RFBs in multi-hour charge-discharge cycles is compromised by an inferior energy efficiency of these systems, and that there are limits on the efficiency improvement due to internal cross-over and the cost of power (at low current densities) and due to an acceptable pressure drop (at high current densities). Differences between lithium-ion and vanadium redox flow batteries (VRFBs) are discussed from the end-user perspective. We conclude, that the area-specific resistance, cross-over current and durability of contemporaneous VRFBs are appropriate for commercialization in multi-hour stationary energy storage markets, and the most import direction in the VRFB development today is the reduction of stack materials and manufacturing costs. Chromium-iron RFBs should be given a renewed attention, since it seems to be the most promising durable low-energy-cost chemistry.

In order to determine the quality of newly produced lithium-ion cells, self-discharge measurements are performed after manufacturing during the so-called aging step. The aging step is a time-consuming and cost-intensive process due to relaxation effects disturbing the self-discharge measuremtens. Relaxation effects are mainly attributed to voltage relaxation and anode overhang equalization. In this work, different methods for electrical self-discharge measurement, such as the voltage decay method, the voltage hold method, and the capacity loss method, were investigated using commercial Samsung INR21700–50E cylindrical cells (NCA/silicon-graphite) and non-commercial pouch-cells (NMC622/graphite). Various preconditioning methods allowed a distinction to be made between undisturbed, short-term, and long-term disturbed cells. While short-term disturbances subsided after several hours, long-term disturbances due to anode overhang were found to significantly disturb all electrical self-discharge measurements for several weeks. A theoretical explanation was introduced, describing the…

O3-type Na[Ni 1/3 Fe 1/3 Mn 1/3 ]O 2 is a promising positive electrode material for sodium-ion batteries. However, it suffers from structural degradation accompanied by surface-impurity growth during ambient storage and processing. In this study, we synthesized Na 1–2y Ca y [Ni 1/3 Fe 1/3 Mn 1/3 ]O 2 with y = 0 and 0.02, and studied their structural stability towards ambient exposure. Na 0.96 Ca 0.02 [Ni 1/3 Fe 1/3 Mn 1/3 ]O 2 demonstrated excellent air stability by retaining 0.93 of lattice Na in the original O3 structure after 6 days of ambient storage. Titration experiments confirmed that the presence of Ca in Na 0.96 Ca 0.02 [Ni 1/3 Fe 1/3 Mn 1/3 ]O 2 effectively suppressed the otherwise rigorous Na + /H + ion exchange in the presence of water. Charge/discharge cycling in half cells suggested that Ca improved the active material’s specific capacity and capacity retention by retaining its structural integrity and eliminating surface impurity formation during ambient electrode processing. Finally, the cycling performance of Na 0.96 Ca 0.02 [Ni 1/3 Fe 1/3 Mn 1/3 ]O 2 /hard carbon…

In recent years, fire and explosion accidents caused by high temperature of lithium-ion batteries have become increasingly frequent, and the safety and reliability of batteries have been of great concern. Battery temperature monitoring is an important means to prevent the occurrence of safety accidents, but at present, it mainly focuses on the external temperature and lacks the monitoring of internal temperature changes and measurement of physical parameters of the battery, which makes it difficult to effectively solve the safety problem of the battery. In this paper, starting from the thermal runaway safety problem faced by Li-ion batteries, we analyze the heat generation principle and temperature effect during battery operation, and discuss various methods of internal battery temperature monitoring, including in situ temperature measurement, multi-parameter measurement inside the battery, temperature measurement based on thin-film sensors and distributed fiber optic sensors, and impedance-based temperature estimation. Also, the advantages and disadvantages of different sensing…

A meaningful benchmarking of battery active materials with inherently different properties requires knowledge of both their intrinsic electrochemical properties as well as of the differences in the resulting porous electrode structures for equal, practically relevant areal capacities. Here we compare graphite and microsilicon anodes with practical areal capacities of 2.8 mAh cm−2 for lithium-ion batteries with regard to their temperature-dependent kinetic charge-transfer resistances (R ct) and their ion transport resistances through the electrolyte phase within the pores of the electrodes (R ion), measured via impedance spectroscopy. We deconvolute the kinetic resistance from the impedance spectra by individually measuring the temperature-dependent pore resistance between −5 and +45 °C, showing that the charge-transfer resistance dominates at low temperatures, while at high temperatures the pore resistance dominates for both electrode types due to the significantly higher activation energy of R ct. An analysis of the potential profile of the electrodes at different lithiation rates…

A high-resolution, 3D, computational fluid dynamics (CFD) model was developed and implemented for simulating the heat and gas generation during thermal runaway failure of an 18650 Li-ion battery cell. The model accounts for volumetric gas generation within the active material of the cell and for gas flow through the jellyroll, into the headspace regions, through the safety vent, and out into the surrounding air space. The simulation captures the key features of the oven test, including: self-heating from decomposition reactions, initial venting (i.e. blowdown), temperature decrease due to evaporative cooling, thermal runaway, a second venting event associated with thermal runaway, and cooldown. The highly detailed geometric model of the safety vent allowed for new insight into the physics of venting during thermal runaway. Secondary flows, including ring vortices, counter-rotating vortex pairs, and corner vortices, were found to increase the rate of mixing of the vented gases with the surrounding air. The simulation was compared to previously reported experimental results and found…

Lithium ion batteries (LIB) have become a cornerstone of the shift to electric transportation. In an attempt to decrease the production load and prolong battery life, understanding different degradation mechanisms in state-of-the-art LIBs is essential. Here, we analyze how operational temperature and state-of-charge (SoC) range in cycling influence the ageing of automotive grade 21700 batteries, extracted from a Tesla 3 Long Range 2018 battery pack with positive electrode containing LiNixCoyAlzO2 (NCA) and negative electrode containing SiOx-C. In the given study we use a combination of electrochemical and material analysis to understand degradation sources in the cell. Herein we show that loss of lithium inventory is the main degradation mode in the cells, with loss of material on the negative electrode as there is a significant contributor when cycled in the low SoC range. Degradation of NCA dominates at elevated temperatures with combination of cycling to high SoC (beyond 50%).

Proton exchange membrane water electrolysis (PEMWE) is an established technology for hydrogen production. To meet the increasing demand and further reduce costs, there is a growing interest in reducing the iridium (Ir) loading. In recent works the complex interface between porous transport layer (PTL) and catalyst layer (CL) was identified as pivotal for PEMWE performance. In this study, this interface was systematically investigated for various Ir loadings and PTL types using a voltage breakdown analysis (VBA) method to differentiate between different sources for overpotential. As expected, the oxygen evolution reaction (OER) overpotential increases with decreasing Ir loading, but its extent depends on the CL/PTL interfacial contact area and the in-plane electrical conductivity of the CL. If the latter is low, this can be partly compensated by using a proper PTL counterpart. However, especially when using low Ir loadings, the VBA method results in inconclusive OER kinetic parameters such as the apparent exchange current density. Therefore, the constant Tafel slope voltage breakdown…

This work proposes a semi-empirical model for the SEI growth process during the early stages of lithium-ion battery formation cycling and aging. By combining a full-cell model which tracks half-cell equilibrium potentials, a zero-dimensional model of SEI growth kinetics, and a semi-empirical description of cell thickness expansion, the resulting model replicated experimental trends measured on a 2.5 Ah pouch cell, including the calculated first-cycle efficiency, measured cell thickness changes, and electrolyte reduction peaks during the first charge dQ/dV signal. This work also introduces an SEI growth boosting formalism that enables a unified description of SEI growth during both cycling and aging. This feature can enable future applications for modeling path-dependent aging over a cell’s life. The model further provides a homogenized representation of multiple SEI reactions enabling the study of both solvent and additive consumption during formation. This work bridges the gap between electrochemical descriptions of SEI growth and applications toward improving industrial battery…

With the growing number of academic researchers focused on lithium-ion batteries, the cell format of choice is often overlooked. Coin cells that utilize either a lithium metal or greatly oversized graphite negative electrode are common but can provide unrealistic testing results when compared to commercial pouch-type cells. Instead, single-layer pouch cells provide a more similar format to those used in industry while not requiring large amounts of active material. Moreover, their assembly process allows for better positive/negative electrode alignment, allowing for assembly of single-layer pouch cells without negative electrode overhang. This work presents a comparison between coin, single-layer pouch, and stacked pouch cells, and shows that single-layer pouch cells without overhang perform best. As well, an Ultra-High Precision Coulometry experiment is performed to show that excess negative or positive electrode coating is detrimental to cell performance. Finally, a guide to assembling reproducible single-layer pouch cells without overhang is presented.

The anode material used in batteries plays a major role in determining their performance. Given its high theoretical capacity, which is ten times more than that of graphite, the anode material routinely used in commercial Lithium-ion batteries (LIB), Si has been recognized as a viable alternative for LIB. With a focus on practical application, prelithiation approaches that are inherently scalable are discussed, characterized, and compared based on their ease of operation, cost, atmospheric stability, compatibility with existing manufacturing processes, homogeneity, and safety. Herein, this review aims to provide (i) a critical investigation of cutting-edge modeling progress for prelithiation strategies and (ii) a summary of the underlying causes of low initial coulombic efficiency (ICE). Mutual learning from these prelithiation processes is anticipated to create more sustainable strategies for manufacturing LIBs.

This paper provides a holistic view of the different studies related to gassing in NMC/graphite lithium-ion batteries over the past couple of decades of scientific development. It underlines the difficulty of predicting the concentration and the proportion of gas released upon cycling and storage and to get a clear mechanistic insight into the reduction and oxidation pathways of electrolyte solvents, the thermal electrolyte degradation, as well as the reactions that involve secondary sources such as water, NMC surface species and cross-talk reactions. Though many relevant experiments such as operando gas analysis using isotope-labeled solvents or two-compartment cells have been conducted, they failed, for instance, to determine the exact mechanism leading to the generation of CO and CO2 gas. Last but not least, this paper discusses different strategies that are currently proposed to reduce or eliminate gassing such as the use of electrolyte additives that enable singlet oxygen quenching or scavenging, NMC coatings that limit the contact with electrolyte and different lithium salts…

Silicon is a promising anode material for lithium-ion batteries due to its high theoretical capacity. However, current lithium-ion batteries with high silicon shares in the anodes suffer from rapid capacity fading. The continuous reformation of the solid electrolyte interphase due to particle volume changes during lithiation consumes cyclable lithium. Direct contact prelithiation is a method to counteract lithium losses during the formation and operation of lithium-ion batteries. By providing excess lithium to the anodes during battery cell production, the cycle life of lithium-ion batteries can be increased. Within this work, the process characteristics of direct contact prelithiation and its effect on battery performance are investigated experimentally. Therefore, silicon-graphite composite anodes were mechanically prelithiated using lithium foil and incorporated in lithium-ion battery pouch cells. The prelithiation time and the cell pressure were systematically varied to obtain insights in to the process behavior. Additionally, the lithium quantity was controlled by lithium foil…

In 2018, a 5/15 kW DC reversible solid oxide cell system was developed and successfully operated by Forschungszentrum Jülich. Based on the knowledge gained with this first system, an optimized system in the power class of 10/40 kW AC was developed afterwards in 2019 that uses the well-established Integrated Module. This module consists of four 20-layer sub-stacks, two heat exchangers and five heating plates. It represents the main components of the system. The basic system layout was retained in general from the previous system and adjusted in accordance with the higher power level, as well as the supporting balance of plant components. The layout of the demonstrator system and its results are described. During the experimental evaluation in fuel cell mode, the system could provide an electrical output power from 1.7 to 13 kW AC . The maximum system efficiency of 63.3% based on the lower heating value (LHV) could be reached at a system power of 10.4 kW AC . This operating point was also analyzed regarding the temperature distribution in the stack and efficiency losses. In…

A major degradation mechanism of polymer electrolyte membrane fuel cells (PEMFCs) in transportation applications is the loss of the electrochemically active surface area ( ECSA ) of platinum cathode catalysts upon dynamic load cycling (resulting in cathode potential cycles). This is commonly investigated by accelerated stress tests (ASTs), cycling the cell voltage under H 2 /N 2 (anode/cathode). Here we examine the degradation of membrane electrode assemblies with Vulcan carbon supported Pt catalysts over extended square-wave voltage cycles between 0.6-1.0 V RHE at 80 °C and 30%-100% RH under either H 2 /N 2 or H 2 /Air; for the latter case, differential reactant flows were used, and the lower potential limit is controlled to correspond to the high-frequency resistance corrected cell voltage, assuring comparable aging conditions. Over the course of the ASTs, changes of the ECSA , the hydrogen crossover current, the proton conduction resistance and the oxygen transport resistance of the cathode electrode, as well as the differential-flow H 2 /O 2 and H 2 /Air performance at 80…

One of the most important edible colours is used in various industries is Sunset Yellow, which is essential to measure according to its consumption. Therefore, a new electrochemical sensor is prepared to measure the food color additives in this work. In this study, CuNiFe2O4 nanospheres to prepare a potent modifier for carbon paste electrode (CPE). Due to environmental toxicity of food color additives, its sensitive, fast and, low-cost determination in workplace environments is of great interest. So, the modified CPE was applied as a sensitivity analysis approach for Sunset Yellow in present Brilliant Blue and Tartarzin in plasma samples. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used as techniques to optimize the analysis and measurement of Sunset Yellow. The calibration curve showed a linear range from 0.5 to 150 μM with a detection limit of 0.15 μM for Sunset Yellow. Simultaneous measurement of three colors, Sunset Yellow, Brilliant Blue and Tartrazine, is done on CPE/CuNiFe2O4 nanospheres surface and in simultaneous measurement received detection…

Mixing graphite with Si particles in anodes of Li-ion batteries provides increased specific energy. In addition, higher Si contents lead to thinner anode coatings at constant areal capacity. In the present study, we systematically investigated the influence of the Si content on the susceptibility of Li plating on Si/graphite anodes. Si/graphite anodes with Si contents from 0 to 20.8 wt% combined with NMC622 cathodes were manufactured on pilot-scale. After initial characterization in coin half cells and by SEM, pouch full cells with fixed N/P ratios were built. Rate capability at different temperatures, and Post-Mortem analysis were carried out. Results from voltage relaxation, Li stripping, SEM measurements, glow discharge optical emission spectroscopy (GD-OES) depth profiling, and optical microscopy were validated against each other. A decreasing susceptibility to Li plating with increasing Si content in the anodes could be clearly observed. A critical C-rate was defined, at which Li plating was detected for the first time. It was also found that at 0 °C the critical C-rate…

The kinetics of passive oxide film formation, its thickening, and composition on Ni-22Cr and Ni-22Cr-6Mo wt% alloys were investigated at selected anodic potentials. Experiments were performed in acidic and alkaline sulfate environments using a number of characterization techniques including a combination of potentiodynamic polarization, on-line atomic emission spectro-electrochemistry (AESEC), in situ potentiostatic passive film growth, along with in situ neutron reflectometry (NR) and ex situ X-ray photoelectron spectroscopy (XPS). The roles of solution pH and Mo on the passivation behavior were discussed in terms of thermodynamic and kinetic factors governing passivation. The pH was found to have an impact on the relative chemical compositions of passive film of the Ni-22Cr alloy but not noticeably for the Ni-22Cr-6Mo alloy. Ni-rich films formed early during the passivation process while Cr(III) enrichment was observed at longer times, albeit less extensively than observed previously in Cl− solutions. The fraction of Cr(III) cations also increased with alloying of Mo at low and…

Increasing the operating voltage of lithium-ion batteries unlocks access to a higher charge capacity and therefore increases the driving range in electric vehicles, but doing so results in accelerated degradation via various mechanisms. A mechanism of particular interest is particle cracking in the positive electrode, resulting in losses in capacity, disconnection of active material, electrolyte side reactions, and gas formation. In this study, NMC811 (LiNi0.8Mn0.1Co0.1O2) half-cells are charged to increasing cut-off voltages, and ex situ X-ray diffraction and X-ray computed tomography are used to conduct post-mortem analysis of electrodes after their first charge in the delithiated state. In doing so, the lattice changes and extent of cracking that occur in early operation are uncovered. The reversibility of these effects is assessed through comparison to discharged cathodes undergoing a full cycle and have been relithiated. Comparisons to pristine lithiated electrodes show an increase in cracking for all electrodes as the voltage increases during delithiation, with the majority of…

To investigate aging effect on the passive film of Ni23Cr15Mo and Ni22Cr9Mo3Nb, synchrotron-based X-ray photoelectron spectroscopy (XPS) was used to analyze the structure and composition of the air-formed passive film on the alloys. The corrosion resistance of the two Ni alloys in 1 M NaCl solution was evaluated with electrochemical cyclic polarization measurement. The synchrotron XPS measurement provided detailed information about chemical states of alloying elements in the passive film, showing that the passive film consists of an inner oxide layer and an outer hydroxide layer. The XPS data allowed precise determination of the chemical composition and the thickness of the outer hydroxide layer, the inner oxide layer, and the underlying subsurface alloy layer. The Cr-oxide in the inner layer grows thicker with aging time, leading to Cr-depletion in the subsurface region. Mo and Nb in the alloy form mixed oxides and hydroxides, and aging in air leads to transformation of the lower valence oxides into higher valence oxides. The freshly formed oxide film exhibits similar barrier…

The rising interest in single-crystalline NCMs (LiMO 2 , M = Ni, Co, Mn) has generated numerous publications which feature promising results in terms of cycle-life improvement when compared to the conventional polycrystalline analogues. To elucidate the effect of the two morphologies on the capacity retention and the internal resistance, this study aims to discriminate the effect of different degradation phenomena of polycrystalline and single-crystalline NCM851005 (LiNi 0.85 Co 0.10 Mn 0.05 O 2 ) in coin full-cells cycled against graphite anodes. The impact of the particle morphology is analyzed over the course of more than 200 charge/discharge cycles for two temperatures of 25 and 45 °C, applying 4.1 or 4.4 V as upper cutoff voltages. The morphology-dependent surface area changes, resulting mainly from the tendency of polycrystalline NCMs towards particle cracking upon calendering, charging, and extended cycling, are quantified via krypton-gas physisorption, and the consequences of particle cracking regarding the amount of gas evolution, transition-metal dissolution, loss of…

Electrochemical sensors have become indispensable tools for the detection and monitoring of food and environmental toxins. In recent years, nanofiber-based materials have emerged as promising candidates for constructing electrochemical sensors, offering a plethora of unique advantages, such as a large surface area, enhanced electron transfer kinetics, and the ability to immobilize diverse recognition elements. This comprehensive review sheds light on the pivotal role of nanofibers in advancing electrochemical sensors for the detection of food and environmental toxins. Various fabrication methods for nanofibers, including electrospinning, template-assisted synthesis, and self-assembly techniques, are elucidated in detail. It highlights the integration of nanofibers as electrode materials, nanocomposites, and immobilization platforms for recognition elements like enzymes, antibodies, and aptamers. The influence of nanofiber properties, encompassing morphology, composition, and surface modification, on the sensing performance is meticulously discussed. Moreover, a comprehensive…

This work tackles the aqueous chemistry of Zr, aiming to contribute to a better understanding of Zr conversion coatings as one of the important contemporary means of corrosion protection. Equilibrium predominance diagrams based on experimentally confirmed Zr–OH and Zr–F aqueous species concerning Zr amorphous solid phase, along with an updated ZrE−pH (Pourbaix) diagram, are constructed. Since ZrO2+existence had been conclusively disproven in both the aqueous and solid states, we chose to depict mononuclear species with ZrOH3+and polynuclear with Zr4(OH)88+. The formation of the Zr solid phase is assumed to include Zr tetrameric species, Zr4(OH)88+, as a fundamental building block thereof. The role of F–and ZrF62–ions in Zr conversion baths and subsequently formed coatings is described. The introduction of ZrF62–anions keeps Zr solvated in the form of a complex, thus preventing the early onset of hydrolysis. The conversion of Zr species and the coating formation mechanism are further discussed from electrochemical and sol-gel perspectives, aiming to give a foundation for future…

Due to environmental and economic concerns, carbon-free aluminium production has been an ultimate goal for aluminium industries. For the past few decades, a considerable amount of research has been conducted to find an inert anode material that could replace the consumable carbon anodes for aluminium electrolysis. Anodic materials such as metals, ceramics and cermets have been studied extensively. All these anode materials have their advantages and disadvantages. However, metal alloys have proven effective due to their resistance to high-temperature corrosion and ability to produce a protective oxide layer. For a successful adaptation of metallic anodes into the aluminium electrolysis cell, an electrolyte with a low-operating temperature and high alumina solubility with good electrical conductivity is required. Another significant component of the carbon-free aluminium electrolysis cell is a wettable cathode to reduce the anode-cathode distance. This review discusses the research progress on inert anodes, wettable cathodes and electrolytes.

Anodic stripping voltammetry (ASV) is a widely used electrochemical analysis method in rapid detection of heavy metals. But the interference in complex samples will influence the accuracy and sensitivity of electrochemical detection, which further limits ASV on-site application. In this article, main ion interferences, interference mechanisms and available elimination measures in ASV detection of heavy metals are analyzed and summarized. Metal ions, the main disturbances, generally interfere with detection by competing active sites, forming intermetallic compounds or coating on electrode surface. Elimination methods include adding masking agents, adjusting electrolyte composition, changing deposition potentials and using modified electrode. More researches about ion interference appear in electrochemical detection method, the effect verification of electrode materials and adding test rather than actual detection. Furthermore, reliable solution of the interferences in simultaneous detection of multiple components will be the direction of future in-depth research.

Proton exchange membrane fuel cells (PEMFCs) typically use Nafion®, which has many drawbacks, such as high cost, fuel crossover, and strenuous synthesis processes. As such, an alternative Nafion®-ionomer free proton conductor has drawn significant interest. Graphene oxide membrane (GOM) is a promising alternative due to its hydrophilic nature and attractive proton conductivity under humidified conditions. However, pristine GOMs have drawbacks, including fuel crossover, a high reduction rate of negatively oxygenated functional groups during fuel cell operation, and proton conductivity showing excessive orientation dependence. We focused on nanocomposite-GOM (N-GOM) based on PFSAs, hydrocarbon polymers, synthetic polymers, inorganic-organic polymers, biopolymers, metal-organic frameworks, and micro- and nano-engineered surfaces. GO nanosheets have outstanding dispersion rate and compatibility with ionomer matrices that can be functionalized by sulfonation, polymerization, phosphorylation, cross-linking, incorporated inorganic nanoparticles, and blending with matrix,…