Journal of The Electrochemical Society

Energy storage systems with Li-ion batteries are increasingly deployed to maintain a robust and resilient grid and facilitate the integration of renewable energy resources. However, appropriate selection of cells for different applications is difficult due to limited public data comparing the most commonly used off-the-shelf Li-ion chemistries under the same operating conditions. This article details a multi-year cycling study of commercial LiFePO₄ (LFP), LiNi_xCo_yAl_1−x−yO₂ (NCA), and LiNi_xMn_yCo_1−x−yO₂ (NMC) cells, varying the discharge rate, depth of discharge (DOD), and environment temperature. The capacity and discharge energy retention, as well as the round-trip efficiency, were compared. Even when operated within manufacturer specifications, the range of cycling conditions had a profound effect on cell degradation, with time to reach 80% capacity varying by thousands of hours and cycle counts among cells of each chemistry. The degradation of cells in this study was compared to that of similar cells in previous studies to identify universal trends and to provide a standard deviation for performance. All cycling files have been made publicly available at batteryarchive.org, a recently developed repository for visualization and comparison of battery data, to facilitate future experimental and modeling efforts.

This year, the battery industry celebrates the 25^th anniversary of the introduction of the lithium ion rechargeable battery by Sony Corporation. The discovery of the system dates back to earlier work by Asahi Kasei in Japan, which used a combination of lower temperature carbons for the negative electrode to prevent solvent degradation and lithium cobalt dioxide modified somewhat from Goodenough's earlier work. The development by Sony was carried out within a few years by bringing together technology in film coating from their magnetic tape division and electrochemical technology from their battery division. The past 25 years has shown rapid growth in the sales and in the benefits of lithium ion in comparison to all the earlier rechargeable battery systems. Recent work on new materials shows that there is a good likelihood that the lithium ion battery will continue to improve in cost, energy, safety and power capability and will be a formidable competitor for some years to come.

In this study, the calendar aging of lithium-ion batteries is investigated at different temperatures for 16 states of charge (SoCs) from 0 to 100%. Three types of 18650 lithium-ion cells, containing different cathode materials, have been examined. Our study demonstrates that calendar aging does not increase steadily with the SoC. Instead, plateau regions, covering SoC intervals of more than 20%–30% of the cell capacity, are observed wherein the capacity fade is similar. Differential voltage analyses confirm that the capacity fade is mainly caused by a shift in the electrode balancing. Furthermore, our study reveals the high impact of the graphite electrode on calendar aging. Lower anode potentials, which aggravate electrolyte reduction and thus promote solid electrolyte interphase growth, have been identified as the main driver of capacity fade during storage. In the high SoC regime where the graphite anode is lithiated more than 50%, the low anode potential accelerates the loss of cyclable lithium, which in turn distorts the electrode balancing. Aging mechanisms induced by high cell potential, such as electrolyte oxidation or transition-metal dissolution, seem to play only a minor role. To maximize battery life, high storage SoCs corresponding to low anode potential should be avoided.

Recently, the field of CO₂ electrolysis has experienced rapid scientific and technological progress. This review focuses specifically on the electrochemical conversion of CO₂ into carbon monoxide (CO), an important "building block" for the chemicals industry. CO₂ electrolysis technologies offer potentially carbon-neutral routes for the production of specialty and commodity chemicals. Many different technologies are actively being pursued. Electrochemical CO₂ reduction from aqueous solutions stems from the success of alkaline and polymer electrolyte membrane electrolyzers for water electrolysis and uses performance metrics established within the field of aqueous electrochemistry. High-temperature CO₂ electrolysis systems rely heavily on experience gained from developing molten carbonate and solid oxide fuel cells, where device performance is evaluated using very different parameters, commonly employed in solid-state electrochemistry. In this review, state-of-the-art low-temperature, molten carbonate, and solid oxide electrolyzers for the production of CO are reviewed, followed by a direct comparison of the three technologies using some of the most common figures of merit from each field. Based on the comparison, high-temperature electrolysis of CO₂ in solid oxide electrolysis cells seems to be a particularly attractive method for electrochemical CO production, owing to its high efficiency and proven durability, even at commercially relevant current densities.

This paper studied the gases release of a graphite//NMC111(LiNi_1/3Mn_1/3Co_1/3O₂) cell during cycle in the voltage ranges of 2.6-4.2V and 2.6-4.8V and the temperatures of at 25°C and 60°C. It was proved that the CO₂, CO, and H₂ gases are released as a result of electrolyte decomposition. And it shows that the CO and H₂ gases evolution is a direct consequence of the electrochemical reaction of electrolyte decomposition, while the CO₂ generation is a consequence of the additional chemical reaction of interaction between the O₂ released from the cathode atomic lattice oxygen and CO released from the same place on the cathode (appearing because of the electrolyte decomposition). That is why at the same electrochemical reaction of electrolyte decomposition, the ratio CO₂/CO varies in the wide range from 0.82 to 2.42 depending on cycling conditions (temperature and cutoff voltage). It was proved that a potential-independent H₂ evolution is a consequence of its adsorption in pores of powdered graphite on anode. There was proposed the mechanism of the electrolyte decomposition and the gases evolution in lithium-ion cells at their cycling, which corresponds quantitatively to all obtained experimental results.

What is the best approach for estimating standard electrochemical potentials, E⁽⁰⁾, from voltammograms that exhibit chemical irreversibility? The lifetimes of the oxidized or reduced forms of the majority of known redox species are considerably shorter than the voltammetry acquisition times, resulting in irreversibility and making the answer to this question of outmost importance. Half-wave potentials, E^(1/2), provide the best experimentally obtainable representation of E⁽⁰⁾. Due to irreversible oxidation or reduction, however, the lack of cathodic or anodic peaks in cyclic voltammograms renders E^(1/2) unattainable. Therefore, we evaluate how closely alternative potentials, readily obtainable from irreversible voltammograms, estimate E⁽⁰⁾. Our analysis reveals that, when E^(1/2) is not available, inflection-point potentials provide the best characterization of redox couples. While peak potentials are the most extensively used descriptor for irreversible systems, they deviate significantly from E⁽⁰⁾, especially at high scan rates. Even for partially irreversible systems, when the cathodic peak is not as pronounced as the anodic one, the half-wave potentials still provide the best estimates for E⁽⁰⁾. The importance of these findings extends beyond the realm of electrochemistry and impacts fields, such as materials engineering, photonics, cell biology, solar energy engineering and neuroscience, where cyclic voltammetry is a key tool.

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

Lithium-ion batteries are well-suited for fully electric and hybrid electric vehicles due to their high specific energy and energy density relative to other rechargeable cell chemistries. However, these batteries have not been widely deployed commercially in these vehicles yet due to safety, cost, and poor low temperature performance, which are all challenges related to battery thermal management. In this paper, a critical review of the available literature on the major thermal issues for lithium-ion batteries is presented. Specific attention is paid to the effects of temperature and thermal management on capacity/power fade, thermal runaway, and pack electrical imbalance and to the performance of lithium-ion cells at cold temperatures. Furthermore, insights gained from previous experimental and modeling investigations are elucidated. These include the need for more accurate heat generation measurements, improved modeling of the heat generation rate, and clarity in the relative magnitudes of the various thermal effects observed at high charge and discharge rates seen in electric vehicle applications. From an analysis of the literature, the requirements for lithium-ion thermal management systems for optimal performance in these applications are suggested, and it is clear that no existing thermal management strategy or technology meets all these requirements.

The standard format for cylindrical Li-ion cells is about to change from 18650-type cells (18mm diameter, 65mm height) to 21700-type cells (21mm diameter, 70mm height). We investigated the properties of five 18650 cells, three of the first commercially available 21700, and three types of the similar 20700 cells in detail. In particular, the (i) specific energy/energy density and electrode thickness, (ii) electrode area and cell resistance, (iii) specific energy as a function of discharge C-rate, as well as (iv) heating behavior due to current flow are analyzed. Finally, the production effort for cells and packs are roughly estimated for 21700 cells compared to 18650 cells.

Lithium-ion batteries (LiB) offer a low-cost, long cycle-life and high energy density solution to the automotive industry. There is a growing need of fast charging batteries for commercial application. However, under certain conditions of high currents and/or low temperatures, the chance for Li plating increases. If the anode surface potential falls below 0 V vs Li/Li⁺, the formation of metallic Li is thermodynamically feasible. Therefore, determination of accurate Li plating curve is crucial in estimating the boundary conditions for battery operation without compromising life and safety. There are various electrochemical and analytical methods that are employed in deducing the Li plating boundary of the Li-ion batteries. The present paper reviews the common test methods and analysis that are currently utilized in Li plating determination. Knowledge gaps are identified, and recommendations are made for the future development in the determination and verification of Li plating curve in terms of modeling and analysis.

Precise control/measurement of electrode potential is significant to understanding and tailoring the electrochemical reactions in high-temperature molten carbonates. However, a highly stable and reproducible reference electrode is still absent in the electrolyte. This work reported an extremely reliable Ni/NiO reference electrode, rather than an Ag⁺/Ag electrode, for molten ternary Li-Na-K carbonates. The selection principle of redox couple and membrane material are systematically investigated by thermodynamic analysis and experimental characterization. The stability, polarization resistance, and potential repeatability of the Ni/NiO reference electrode were evaluated by electrochemical measurements. The linear sweep voltammetry (LSV) results showed that the potential change was less than 17.3 mV within 120 h. The electrode potential could be restored quickly after large-current polarization. The minimum potential difference among parallel reference electrodes is 0.81 mV, demonstrating an excellent reproducibility of the Ni/NiO reference electrode. Overall, the novel reference electrode based on the Ni/NiO redox couple and the mullite membrane possessed potential long-term stability, excellent polarization resistance, and potential repeatability in molten carbonates.

The electrolytes of the today omnipresent lithium-ion batteries (LIBs) have for more than 25 years been based upon 1 M LiPF₆ in a 50:50 EC:DMC mixture—commonly known as LP30. The success of the basic design of the LP30 electrolyte, with many variations and additions made over the years, is unchallenged. Yet, some molecular level fundamentals of LP30 are surprisingly elusive: the structure of the first solvation shell of the Li⁺ cation is still a topic of current debate; the details of the dynamics are not fully understood; the interpretation of structural and dynamic properties is highly dependent on the analysis methods used; the contributions by different species to the ion transport and the energetics involved are not established. We here apply dynamic structure discovery analysis as implemented in CHAMPION to molecular dynamics simulation trajectories to bring new light on the structure and dynamics within LP30 and especially the (Li⁺) ion transport to rationalize further development of LIB electrolytes.

Gold nanoparticles/poly(p-aminobenzenesulfonic acid)/multi-walled carbon nanotubes modified glassy carbon electrode (NanoAu/Poly(ABSA)/MWCNTs/GCE) was prepared for electrochemically determining catechol (CAT) and hydroquinone (HQ) by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Results showed that CAT and HQ were electrochemically seperated well, and the difference between oxidation peak potentials of CAT and HQ was 111 mV. The redox currents of CAT and HQ were significantly enhanced on NanoAu/PABSA/MWCNTs/GCE, as compared with on bare GCE. The oxidation peak current (I_pa) of 10 μM CAT was 0.24 μA, and there was almost no detected oxidation current response for 10 μM HQ on bare GCE. The I_pa values on NanoAu/Poly(ABSA)/MWCNTs/GCE increased to 11.3 times for CAT as compared with on GCE, 1.5 times for CAT and 2.5 times for HQ as compared with on MWCNTs/GCE. The linear range of CAT and HQ measurments on NanoAu/Poly(ABSA)/MWCNTs/GCE was 2 ∼ 200 μM, and the limit of detection (LOD, S/N = 3) was 1.5 μM for CAT and 1.0 μM for HQ. This sensor showed high detection sensitivity for CAT (16.53 μA·μM^–1·cm^–2) and HQ (17.68 μA·μM^–1·cm^–2). The sensor had been applied for CAT and HQ measurement in lake water with satisfactory results.

A quantitative link between crack evolution in lithium-ion positive electrodes and the degrading performance on cells is not yet well established nor is any single technique capable of doing so widely available. Here, we demonstrate a widely accessible high-throughput approach to quantifying crack evolution within electrodes. The approach applies super-resolution scanning electron microscopy (SEM) imaging of cross-sectioned NMC532 electrodes, followed by segmentation and quantification of crack features. Crack properties such as crack intensity, crack width and length are quantified as a function of charge rate (1C, 6C, and 9C) and cycle number (25, 225, and 600 cycles). Hundreds of particles are characterized for statistical confidence in the quantitative crack measurements. The data on crack evolution is compared to electrochemical data from full cells and half cells with the NMC532 positive electrodes. We show that while crack evolution strongly correlates with capacity fade in the first 25 cycles, it does not correlate well for the following hundreds of cycles indicating that cracking may not be the dominant cause of capacity fade throughout the cycle-life of cells.

Zinc-based energy storage is increasingly getting attention owing to its outstanding characteristics over to the other systems. Their high abundance, user-friendliness, environmental benignity, and low reduction potential which can avoid unwanted hydrogen evolution are some of the attractive features. Appropriate membrane selection for the zinc-based redox flow battery is challenging. Herein we report the composite of SPEEK (sulfonated polyether ether ketones) with covalent organic frameworks (COF) as a potential membrane for zinc-based redox flow battery. Biphenyl-based knitting type COF was prepared, post sulfonated and blended with SPEEK. In a Zn/I₂ redox flow battery system, the discharge capacity was found to be 19.8 AhL⁻¹, 17.4 AhL⁻¹, 15.1 AhL⁻¹ for 20%, 15%, 10% SCOF loading respectively against 14.5 AhL⁻¹ for pristine SPEEK at 20 mAcm⁻² current density. The capacity was improved by about 36% higher than the neat SPEEK membrane. This improvement in the battery performance might be due to the higher ionic conductivity and hydrophilicity after SCOF loading. We found that the 15% loading was the maximum limit for the battery performance, beyond which the energy efficiency was found to be fading, which is due to the excessive dendrite growth on the membrane surface.

The scarcity of fresh water resource has become one of the top concerns of modern society. Various water treatment technologies have been developed for the reuse of seawater and capacitive deionization (CDI) holds superior advantages as a promising electrosorption desalination technology. Since electrode material is the key factor in controlling the performance of CDI, recent years have witnessed considerable research progress in the rational design and fabrication of Zn-based MOF-derived carbon materials applied as electrode materials for CDI. In this review, Zn-based MOF-derived carbon materials, including MOF-5 derived carbons, ZIF-8 derived carbons and innovation Zn-based MOF derived carbons, are systematically overviewed based on their MOF template precursors. Among them, ZIF-8 derived carbon electrode materials are summarized in detail and different approaches for the improvement of their CDI performance are particularly discussed. We believe this review could function as a guidance of innovative development of Zn-based MOF-derived carbon materials and provide future directions for further improving their CDI performance.

Emphasis on clean energy has led to a widespread focus on lithium-ion batteries. However, a major obstacle is their degradation with several cycles or calendar aging. Battery Management System relies on an essential model-based algorithm to protect the battery from operating outside the safety limit. Thus, this work attempts to answer important research questions on battery models: (1) Are physics-based electrochemical models (EM) robust enough to identify internal cell degradation and abnormal battery behavior? (2) How are the structural simplifications and mathematical order reductions imposed on the EMs and what are their trade-offs? (3) How to apply simplified EM for safer and more efficient battery operation? (4) What are the prospects and obstacles of employing EM-based algorithms in the future? This paper presents a detailed analysis of EM from a modeling and application perspective. The paper introduces battery operating mechanisms, typical failures, and their effects. Followed by an analysis of full order EM (Pseudo 2-Dimensional), and further classification into simpler and advanced reduced-order models. The study demonstrates the gaps in theoretical understanding and their implementation for real-time battery operations such as in thermal management, energy utilization, and fault diagnosis and prognosis.

A review of experimental author's works proving the existence of the phenomenon of the electrochemical phase formation in metals and alloys via a supercooled liquid state stage is presented. The research findings focused on the electrochemical formation of metastable structures and intermediate phases, as well as on the structural features accompanying them. Electrochemical amorphous phase formation in metals and alloys, electrochemical quasicrystalline phase formation in metals, and electrochemical polymorphic phase formation in metals are discussed. Electrochemical hydrogen-related structure formation in metals, electrochemical high-defect crystalline phase formation in metals, and electrochemical texture-inhomogeneous structure formation in metals are considered. Electrochemical formation of intermediate phases in metals and alloys, electrochemical formation of eutectics in metallic alloys, and electrochemical formation of chemical compounds at the metallic cathode/electrodepositing metal interface are analyzed. Electrochemical reduction of ions in metals and alloys at a liquid cathode versus a solid chemically identical one, electrochemical phase formation of metals at chemically identical solid or liquid cathode, and electrochemical phase formation of alloys at chemically identical solid or liquid cathode are discussed.

Lithium plating on the negative electrode of Li-ion batteries remains as a great concern for durability, reliability and safety in operation under low temperatures and fast charging conditions. High-accuracy detection of Li-plating is critically needed for field operations. To detect the lithium plating is to track its multiphysics footprint since lithium plating often is a localized event while the driving force from chemical, electrical, thermal and mechanical origins could vary with time and locality which makes the detection and characterization challenging. Here, we summarize the multiphysical footprints of lithium plating and the corresponding state-of-the-art detection methods. By assessing and comparing these methods, the combination of capacity/voltage differential, R–Q mapping and Arrhenius outlier tracking could be promising and effective for battery diagnosis, prognosis and management. We analyze the origins of quantitative error in sample preparation, overly simplified assumption and dynamic evolution of the plated Li, and recommend the in situ and quantitative chemical analysis method, such as in situ NMR, EPR, X-ray and neutron. In addition, we propose the four conjectures on the capacity plunge, lithium plating, pore clogging, electrolyte drainage and rapid SEI growth, can be aligned and unified to one scenario basically triggered by lithium plating.

Epitaxial electrodeposition of Co, Cu and Ru is compared and contrasted. The seed layer for electrodeposition of all three metals was an epitaxial Ru(0001) film that was deposited at an elevated temperature onto a sapphire(0001) substrate and annealed post deposition. The epitaxial orientation relationship of the electrodeposited film and the seed layer, the epitaxial misfit strain, the role of symmetry of the seed layer versus the electrodepositing layer is addressed. In addition, the impact of underpotential deposition on film nucleation, and the growth morphology of the films is discussed. It is shown that epitaxial electrodeposition of metallic films to thicknesses of tens of nanometers is readily achievable.

This paper 1189 was presented during the 241st Meeting of the Electrochemical Society, May 29–June 2, 2022.

Emphasis on clean energy has led to a widespread focus on lithium-ion batteries. However, a major obstacle is their degradation with several cycles or calendar aging. Battery Management System relies on an essential model-based algorithm to protect the battery from operating outside the safety limit. Thus, this work attempts to answer important research questions on battery models: (1) Are physics-based electrochemical models (EM) robust enough to identify internal cell degradation and abnormal battery behavior? (2) How are the structural simplifications and mathematical order reductions imposed on the EMs and what are their trade-offs? (3) How to apply simplified EM for safer and more efficient battery operation? (4) What are the prospects and obstacles of employing EM-based algorithms in the future? This paper presents a detailed analysis of EM from a modeling and application perspective. The paper introduces battery operating mechanisms, typical failures, and their effects. Followed by an analysis of full order EM (Pseudo 2-Dimensional), and further classification into simpler and advanced reduced-order models. The study demonstrates the gaps in theoretical understanding and their implementation for real-time battery operations such as in thermal management, energy utilization, and fault diagnosis and prognosis.

Lithium (Li) metal anodes are essential for developing next-generation high-energy-density batteries. However, Li dendrite/whisker formation caused short-circuiting issue and short cycle life have prevented lithium metal from being viably used in rechargeable batteries. Numerous works have been done to study how to regulate the Li growth in electrochemical cycling by using external stacking forces. While it is widely agreed that stack pressure positively affects the lithium plating/stripping process, the optimized pressure range provided by different works varies greatly because of the difference in the pressure control setup. In this work, a pressure control apparatus is designed for Li metal batteries with liquid and solid-state electrolytes (SSE). With considerations of minimizing cell to cell variation, a reusable split cell and pressure load cell are made for testing electrochemical cells with high precision pressure control. The capability of the designed setup is demonstrated by studying the pressure effect on the Li plating/stripping process.

Ternary metal halides A₃MX₆, (A = Li⁺, Na⁺; M = trivalent metal; X = halide) are a promising family of solid electrolytes for potential applications in all-solid-state batteries. Recent research efforts have demonstrated that chemical substitution at all three sites is an effective strategy to controlling battery-relevant material properties. The A₃MX₆ family exhibits a wide breadth of structure and anion sublattice types, making it worthwhile to comprehend how chemical substitutions manifest desirable functional properties including ion transport, electrochemical stability, and environmental tolerance. Yet, a cohesive understanding of the materials design principles for these substitutions have not yet been developed. Here, we bring together prior literature focused on chemical substitutions in the A₃MX₆ ternary metal halide solid electrolytes. Using materials chemistry perspectives and principles, we aim to provide insights into the relationships between crystal structure, choice of substituting ions and the extent of substitutions, ionic conductivity, and electrochemical stability. We further present targeted approaches to future substitution studies to enable transformative advances in A₃MX₆ solid electrolytes and all-solid-state batteries.

Active cathode material and graphite anode material are routinely mixed with conductor and binder to improve the electric conductivity and mechanical stability of electrodes. Despite its benefits, this carbon binder domain (CBD) impedes ionic transport and reduces the active surface area, thus impacting the battery performance. We consider a composite spherical particle, whose active-material core is coated with CBD, and its homogeneous counterpart, for which we derived equivalent electrical conductivity, ionic diffusivity, and reaction parameters in the Butler-Volmer equation. These equivalent characteristics are defined to ensure that the same mass and charge enter the composite and homogenized spheres. They are expressed in terms of the volume fraction of the active material and transport properties of the active material and CBD. In general, the equivalent effective diffusion coefficient and reaction parameters are time-dependent and exhibit two-stage behavior characterized by the reaction delay time. At later times, these characteristics are time-independent and given explicitly by closed-form formulae. The simplicity of these expressions facilitates their use in single- and multi-particle representations of Li-ion and Li-metal batteries.

A model for impedance of a PEM fuel cell cathode taking into account oxygen transport in the cathode catalyst layer (CCL), gas–diffusion layer (GDL) and in channel is solved analytically. A formula for the cathode impedance is valid for the cell current densities below 100 mA cm⁻² and air flow stoichiometries exceeding 10. Least–squares fitting of experimental spectrum using the analytical result takes about 5 s on a standard PC. Fitting returns Tafel slope of the oxygen reduction reaction, double layer capacitance, CCL proton conductivity and oxygen diffusivities of the CCL and GDL. Analytical impedance can be coded as a user–defined function for a standard spectra fitting software supplied with EIS–meters.

The electrolytes of the today omnipresent lithium-ion batteries (LIBs) have for more than 25 years been based upon 1 M LiPF₆ in a 50:50 EC:DMC mixture—commonly known as LP30. The success of the basic design of the LP30 electrolyte, with many variations and additions made over the years, is unchallenged. Yet, some molecular level fundamentals of LP30 are surprisingly elusive: the structure of the first solvation shell of the Li⁺ cation is still a topic of current debate; the details of the dynamics are not fully understood; the interpretation of structural and dynamic properties is highly dependent on the analysis methods used; the contributions by different species to the ion transport and the energetics involved are not established. We here apply dynamic structure discovery analysis as implemented in CHAMPION to molecular dynamics simulation trajectories to bring new light on the structure and dynamics within LP30 and especially the (Li⁺) ion transport to rationalize further development of LIB electrolytes.

A quantitative link between crack evolution in lithium-ion positive electrodes and the degrading performance on cells is not yet well established nor is any single technique capable of doing so widely available. Here, we demonstrate a widely accessible high-throughput approach to quantifying crack evolution within electrodes. The approach applies super-resolution scanning electron microscopy (SEM) imaging of cross-sectioned NMC532 electrodes, followed by segmentation and quantification of crack features. Crack properties such as crack intensity, crack width and length are quantified as a function of charge rate (1C, 6C, and 9C) and cycle number (25, 225, and 600 cycles). Hundreds of particles are characterized for statistical confidence in the quantitative crack measurements. The data on crack evolution is compared to electrochemical data from full cells and half cells with the NMC532 positive electrodes. We show that while crack evolution strongly correlates with capacity fade in the first 25 cycles, it does not correlate well for the following hundreds of cycles indicating that cracking may not be the dominant cause of capacity fade throughout the cycle-life of cells.

Conventional battery simulation tools offer current, voltage, and power operating modes. This article presents General Operating Modes (GOMs), which move beyond these standard modes and allow battery models of any scale to simulate novel operating modes such as constant temperature, constant lithium plating overpotential, and constant concentration. The governing equations of the battery model are solved alongside a single algebraic constraint that determines the current. The operating modes are simulated efficiently and deterministically inside a differential-algebraic equation (DAE) solver, and constraints are satisfied within solver tolerances. We propose a mixed-continuous discrete (aka hybrid) solution to the constrained charging problem, using the GOMs to satisfy charging constraints. This approach enables nonlinear model predictive control (NMPC) to be implementable in real-time while directly using sophisticated physics-based battery models. The approach is demonstrated for three models of various complexity: a thin-film nickel hydroxide electrode model, a Single-Particle (SP) model, and a Porous Electrode Theory (PET) model. The hybrid fast charging algorithm is shown to be slightly suboptimal for the thermal SP model in some cases, which is not of practical importance for NMPC.

LiFePO₄/graphite (LFP), Li[Ni_0.5Mn_0.3Co_0.2]O₂/graphite (NMC3.8 V, balanced for 3.8 V cut-off), and Li[Ni_0.83Mn_0.06Co_0.11]O₂/graphite (Ni83, balanced for 4.06 V cut-off) cells were tested at 85 °C. Three strategies were used to improve cell lifetime for all positive electrode materials at 85°C. First, low voltage operation (<4.0 V) was used to limit the parasitic reactions at the positive electrode. Second, LiFSI (lithium bis(trifluoromethanesulfonyl)imide) was used as the electrolyte salt for its superior thermal stability over LiPF₆ (lithium hexafluorophosphate). The low voltage operation avoids the aluminum corrosion seen at higher voltages with LiFSI. NMC3.8 V cells were operated at 6 C charge and 6 C discharge without issue for 2500 cycles and then moved to room temperature where normal operation was obtained. Finally, dimethyl-2,5-dioxahexane carboxylate (DMOHC) was used as a sole electrolyte solvent or mixed with dimethyl carbonate. μ-XRF data showed no detectable levels of transition metal deposition on the negative electrode of Ni83 and LFP cells, and DMOHC cells showed less gassing after testing compared to EC-based electrolytes. We found incredible capacity retention and cycle life for Ni83 and NMC3.8 V cells using DMOHC and LiFSI at 70 °C and at 85 °C in tests that ran for more than 6 and 5 months (and are still running), respectively.

To determine whether large sudden pH and Cl⁻ concentration changes occur during the crevice corrosion of Fe-16Cr, as in the case of Fe-18Cr-10Ni-5.4Mn, simultaneous measurement of the pH and Cl⁻ concentration was performed in 0.01 M NaCl (pH 3.0). The corrosivity of the crevice solution was different before and after crevice corrosion initiation, and the sudden changes in the pH and Cl⁻ concentration inside the crevice were the same as those for Fe-18Cr-10Ni-5.4Mn. The incubation period was characterized by weak acidification (pH 1.6−2.0) and a small accumulation of Cl⁻ (0.1−0.3 M). The growth period was characterized by strong acidification (pH ≤ 1.0) and a large accumulation of Cl⁻ (≥1.0 M). At the crevice corrosion initiation site, a metastable pit was observed and a S signal was detected from the residual in the pit. It can be concluded that the crevice corrosion of Type 430 stainless steels is initiated by Cl⁻, which generates metastable pitting at sulfide inclusions. The effect of the electrode potential on the pH and Cl⁻ concentration was investigated in 0.01 M NaCl from −0.05 to 0.1 V. No effect of potential was observed during both the crevice corrosion incubation and growth periods.

Lithium-sulfur batteries (LSBs) are considered a very attractive alternative to lithium-ion batteries due to their high theoretical capacity and the low cost of the active materials. However, the realization of LSBs remains hostage to many challenges associated with the cathode and anode response to the electrochemical conditions inside the battery cell. While working with LSBs, elemental sulfur undergoes multielectron reduction reactions until it is reduced to Li2S. The intermediate long chain lithium-polysulfide (LiPS) species are soluble, and hence diffuse through the electrolyte solution from the cathode side to the anode. This “shuttle” phenomenon is considered to be one of the main issues of LSB. Most effort in investigating LSBs has focused on the cathode side while few have considered the importance of the lithium anode reversibility and the separator role in preventing the “shuttle” phenomenon. In the current work, we use atomic layer deposition to successfully coat a standard polypropylene separator with an additional layer of metal oxides thin film. We show that surface treatment of the separator facilitated improved electrochemical response, and suppressed the shuttling of LiPS to the anode

The influence of different combinations of accelerated stress test (AST) protocols simulating load-cycle and start/stop conditions of a proton exchange membrane fuel cell (PEMFC) vehicle is investigated on a bimodal Pt/C catalyst. The bimodal Pt/C catalyst, prepared by mixing two commercial catalysts, serves as a model system and consists of two distinguishable size populations. The change in mean particle size was investigated by in situ small-angle X-ray scattering (SAXS). The comparison to the reference catalysts, i.e., the two single-size population catalysts, uncovers the presence of electrochemical Ostwald ripening as a degradation mechanism in the bimodal catalyst. Increasing the harshness of the applied AST protocol combinations by faster changing between load-cycle or start/stop conditions, the particle size of the larger population of the bimodal catalyst increases faster than expected. Surprisingly, the change in mean particle size of the smaller size population indicates a smaller increase for harsher AST protocols, which might be explained by a substantial electrochemical Ostwald ripening.

The cell-to-cell electrical contact resistance was investigated to estimate the effect of faulty electrical contact point(FECP) on the performance of battery packs. The temperature of the FECP in series circuit rises instantaneously compared to that of other normal points after the start of the current load, but the temperature of the FECP in parallel circuit rises just after the voltage turning point at the end of the charging/discharging process. The voltage difference between the highest voltage and the lowest voltage of the cells at the end of discharge stage increases apparently while the battery pack contains the FECPs, which is a typical feature during the decay of battery packs. In this study, the capacity retention of LiFePO₄/C battery at room temperature reaches to 80% after 1260 cycles for a 1p3s pack, 1210 cycles for a 3p3s pack and 1510 cycles for a single cell, in which the average cell-to-cell connector impedance is 0.13 mΩ in the circuit. By contrast, the cyclic charge-discharge stops at 381st cycle for a 1p3s pack with a FECP(0.42 mΩ) in series circuit and at 1097th cycle for a 3p3s pack with a FECP(0.41 mΩ) in parallel circuit.

Electrochemical activity of different MnO₂ phases as electrodes of aluminium-ion batteries (AIBs) is studied. For this purpose, different simple synthesis routes have been carried out to obtain different structures and morphologies: rod-like with tunnelled structure (α-MnO₂) and hexagonal micro-pellets with lamellar structure (δ-MnO₂). α-MnO₂ showed an outstanding capacity (Q) of 120 mA h g⁻¹ at current densities of 100 mA g⁻¹, which remained stable after 100 cycles with efficiencies over 90%. δ-MnO₂ showed a good Q of 80 mA h g⁻¹ at current densities of 50 mA g⁻¹ after 50 cycles with efficiencies over 95%. Moreover, cyclic voltammetry (CV) measurements at different rates allowed for a better understanding of the electrochemical behaviour and revealed the contribution relation of diffusive and capacitive-controlled mechanisms in the corresponding AIB system. Besides, cyclic voltammetry (CV) measurements at different rates allowed a kinetic study of the diffusive and capacitive-controlled mechanisms. Conclusions were obtained regarding the dimensionality of α-MnO₂ (1D) and δ-MnO₂ (2D) and their electrochemical behaviour in AIBs−1

A newly synthesized electrolyte additive, lithium trifluoro(cyano) borate (LiBF3CN), has been investigated for electrochemical performance improvement of lithium metal batteries. The LiBF3CN has a structure where one fluorine atom of BF4- is substituted with a cyano group (-CN) prepared by the reaction of boron trifluoride etherate with lithium cyanide. The electrochemical performance in symmetric Li/Li cells and NCM523/Li cells is significantly improved upon the incorporation of LiBF3CN as an electrolyte additive into a carbonate-based electrolyte. Extensive characterization of the deposited lithium metal reveals that a thin (≈ 20 nm) and robust solid electrolyte interphase composed of LiNxOy, Li3N and Li2O is formed by the reductive decomposition of the LiBF3CN additive, which plays an important role in decreasing the resistance and stabilizing lithium deposition/stripping. The insight into the substitution effect of a functional group obtained from this work provides guidance for the design of new electrolyte additives.