Battery research depends upon up-to-date information on the cell characteristics found in current electric vehicles, which is exacerbated by the deployment of novel formats and architectures. This necessitates open access to cell characterization data. Therefore, this study examines the architecture and performance of first-generation Tesla 4680 cells in detail, both by electrical characterization and thermal investigations at cell-level and by disassembling one cell down to the material level including a three-electrode analysis. The cell teardown reveals the complex cell architecture with electrode disks of hexagonal symmetry as well as an electrode winding consisting of a double-sided and homogeneously coated cathode and anode, two separators and no mandrel. A solvent-free anode fabrication and coating process can be derived. Energy-dispersive X-ray spectroscopy as well as differential voltage, incremental capacity and three-electrode analysis confirm a NMC811 cathode and a pure graphite anode without silicon. On cell-level, energy densities of 622.4 Wh/L and 232.5 Wh/kg were determined while characteristic state-of-charge dependencies regarding resistance and impedance behavior are revealed using hybrid pulse power characterization and electrochemical impedance spectroscopy. A comparatively high surface temperature of ∼70 °C is observed when charging at 2C without active cooling. All measurement data of this characterization study are provided as open source.
The Electrochemical Society (ECS) was founded in 1902 to advance the theory and practice at the forefront of electrochemical and solid state science and technology, and allied subjects.
ISSN: 1945-7111
JES is the flagship journal of The Electrochemical Society. Published continuously from 1902 to the present, JES remains one of the most highly-cited journals in electrochemistry and solid-state science and technology.
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Manuel Ank et al 2023 J. Electrochem. Soc. 170 120536
Yuliya Preger et al 2020 J. Electrochem. Soc. 167 120532
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), LiNixCoyAl1−x−yO2 (NCA), and LiNixMnyCo1−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.
George E. Blomgren 2017 J. Electrochem. Soc. 164 A5019
This year, the battery industry celebrates the 25th 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.
Peter Keil et al 2016 J. Electrochem. Soc. 163 A1872
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.
Jorn M. Reniers et al 2019 J. Electrochem. Soc. 166 A3189
The maximum energy that lithium-ion batteries can store decreases as they are used because of various irreversible degradation mechanisms. Many models of degradation have been proposed in the literature, sometimes with a small experimental data set for validation. However, a comprehensive comparison between different model predictions is lacking, making it difficult to select modelling approaches which can explain the degradation trends actually observed from data. Here, various degradation models from literature are implemented within a single particle model framework and their behavior is compared. It is shown that many different models can be fitted to a small experimental data set. The interactions between different models are simulated, showing how some of the models accelerate degradation in other models, altering the overall degradation trend. The effects of operating conditions on the various degradation models is simulated. This identifies which models are enhanced by which operating conditions and might therefore explain specific degradation trends observed in data. Finally, it is shown how a combination of different models is needed to capture different degradation trends observed in a large experimental data set. Vice versa, only a large data set enables to properly select the models which best explain the observed degradation.
Weilong Ai et al 2020 J. Electrochem. Soc. 167 013512
Whilst extensive research has been conducted on the effects of temperature in lithium-ion batteries, mechanical effects have not received as much attention despite their importance. In this work, the stress response in electrode particles is investigated through a pseudo-2D model with mechanically coupled diffusion physics. This model can predict the voltage, temperature and thickness change for a lithium cobalt oxide-graphite pouch cell agreeing well with experimental results. Simulations show that the stress level is overestimated by up to 50% using the standard pseudo-2D model (without stress enhanced diffusion), and stresses can accelerate the diffusion in solid phases and increase the discharge cell capacity by 5.4%. The evolution of stresses inside electrode particles and the stress inhomogeneity through the battery electrode have been illustrated. The stress level is determined by the gradients of lithium concentration, and large stresses are generated at the electrode-separator interface when high C-rates are applied, e.g. fast charging. The results can explain the experimental results of particle fragmentation close to the separator and provide novel insights to understand the local aging behaviors of battery cells and to inform improved battery control algorithms for longer lifetimes.
Xia Cao et al 2021 J. Electrochem. Soc. 168 010522
The conventional LiPF6/carbonate-based electrolytes have been widely used in graphite (Gr)-based lithium (Li) ion batteries (LIBs) for more than 30 years because a stable solid electrolyte interphase (SEI) layer forms on the graphite surface and enables its long-term cycling stability. However, few of these electrolytes are stable under the more stringent conditions needed with a Li metal anode (LMA) and other anodes, such as silicon (Si), which exhibit large volume changes during charge/discharge processes. Many different approaches have been developed lately to stabilize Li metal batteries (LMBs) and Si-based LIBs. From this aspect, localized high-concentration electrolytes (LHCEs) have unique advantages: not only are they stable in a wide electrochemical window, they can also form stable SEI layers on LMA and Si anode surfaces to enable their long-term cycling stability. The ultrathin SEI layer formed on a Gr anode can also improve the safety and high-rate operation of conventional LIBs. In this paper, we give a brief summary of our recent work on LHCEs, including their design principle and applications in both LMBs and LIBs. A perspective on the future development of LHCEs is also discussed.
E. Peled and S. Menkin 2017 J. Electrochem. Soc. 164 A1703
The Solid-Electrolyte-Interphase (SEI) model for non-aqueous alkali-metal batteries constitutes a paradigm change in the understanding of lithium batteries and has thus enabled the development of safer, durable, higher-power and lower-cost lithium batteries for portable and EV applications. Prior to the publication of the SEI model (1979), researchers used the Butler-Volmer equation, in which a direct electron transfer from the electrode to lithium cations in the solution is assumed. The SEI model proved that this is a mistaken concept and that, in practice, the transfer of electrons from the electrode to the solution in a lithium battery, must be prevented, since it will result in fast self-discharge of the active materials and poor battery performance. This model provides [E. Peled, in "Lithium Batteries," J.P. Gabano (ed), Academic Press, (1983), E. Peled, J. Electrochem. Soc., 126, 2047 (1979).] new equations for: electrode kinetics (io and b), anode corrosion, SEI resistivity and growth rate and irreversible capacity loss of lithium-ion batteries. This model became a cornerstone in the science and technology of lithium batteries. This paper reviews the past, present and the future of SEI batteries.
Kevin G. Gallagher et al 2016 J. Electrochem. Soc. 163 A138
Increasing the areal capacity or electrode thickness in lithium ion batteries is one possible means to increase pack level energy density while simultaneously lowering cost. The physics that limit use of high areal capacity as a function of battery power to energy ratio are poorly understood and thus most currently produced automotive lithium ion cells utilize modest loadings to ensure long life over the vehicle battery operation. Here we show electrolyte transport limits the utilization of the positive electrode at critical C-rates during discharge; whereas, a combination of electrolyte transport and polarization lead to lithium plating in the graphite electrode during charge. Experimental measurements are compared with theoretical predictions based on concentrated solution and porous electrode theories. An analytical expression is derived to provide design criteria for long lived operation based on the physical properties of the electrode and electrolyte. Finally, a guideline is proposed that graphite cells should avoid charge current densities near or above 4 mA/cm2 unless additional precautions have been made to avoid deleterious side reaction.
Chang-Hui Chen et al 2020 J. Electrochem. Soc. 167 080534
Presented here, is an extensive 35 parameter experimental data set of a cylindrical 21700 commercial cell (LGM50), for an electrochemical pseudo-two-dimensional (P2D) model. The experimental methodologies for tear-down and subsequent chemical, physical, electrochemical kinetics and thermodynamic analysis, and their accuracy and validity are discussed. Chemical analysis of the LGM50 cell shows that it is comprised of a NMC 811 positive electrode and bi-component Graphite-SiOx negative electrode. The thermodynamic open circuit voltages (OCV) and lithium stoichiometry in the electrode are obtained using galvanostatic intermittent titration technique (GITT) in half cell and three-electrode full cell configurations. The activation energy and exchange current coefficient through electrochemical impedance spectroscopy (EIS) measurements. Apparent diffusion coefficients are estimated using the Sand equation on the voltage transient during the current pulse; an expansion factor was applied to the bi-component negative electrode data to reflect the average change in effective surface area during lithiation. The 35 parameters are applied within a P2D model to show the fit to experimental validation LGM50 cell discharge and relaxation voltage profiles at room temperature. The accuracy and validity of the processes and the techniques in the determination of these parameters are discussed, including opportunities for further modelling and data analysis improvements.
Latest articles
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Deyong Kang et al 2024 J. Electrochem. Soc. 171 037526
Squamous cell carcinoma antigen (SCCA) is an important biomarker in the diagnose of cancer, so developing effective methods for its detection is of great significance. In the present work, a novel sandwich-like electrochemical immunosensing assay (STEM) of SCCA was constructed by preparing gold nanoparticle/reduced graphene-oxide (Au NPs/rGO) to immobilize primary antibody (PAb) of SCCA and UIO-66-NH2 MOFs structure to immobilize second antibody (SAb) and electroactive toluidine blue (Tb) probe. In this designed STEM assay, the prepared Au NPs/rGO nanohybrid offers the advantages in large surface area and conductivity as carrier, and UIO-66-NH2 provided an ideal platform to accommodate SAb and a large number of Tb molecules as signal amplifier. In the existence of SCCA, the current peaks of Tb from the formed STEM structure increase with the increase of SCCA level. After optimizing the related control factors, a wide linear range (0.01 pg ml−1 and 15.0 ng ml−1) and very low detection limit (0.003 pg ml−1) of SCCA was achieved, it's thus expected the designed STEM strategy has important applications for the detection of SCCA.
Highlights
A novel sandwich-like electrochemical immunosensing assay was designed for squamous cell carcinoma antigen detection
UIO-66-NH2 was used to assemble second antibody and toluidine blue as amplifier
The designed immunosensing assay exhibits superior analytical performances
The detection limit for squamous cell carcinoma antigen is low to 0.003 pg ml−1
Katrina Ramirez-Meyers et al 2024 J. Electrochem. Soc. 171 030524
MnO2, in its many phases, is abundant, non-flammable, non-toxic, reliable, made with abundant materials using simple manufacturing methods, and can have a high theoretical capacity for some phases (up to 617 mAh g−1). Here we have investigated the sensitivity of the performance ofbirnessite—produced in situ—to the presence of Bi2O3, depth-of-discharge, electrolyte salt type, and relative electrolyte volume. We prepared cathodes composed of 45 wt% MnO2, 22.5 wt% Bi2O3, and 22.5 wt% carbon additives, and compared cycling stability in two electrolytes—6.6 M KOH (27 wt%) and 6.6 M NaOH (21 wt%), and two types of 3-electrode test fixtures (flooded beaker or electrolyte-lean T-cell). Our results showed that birnessite can be synthesized electrochemically in NaOH, and cycling the cathode in NaOH improves its stability when compared to cycling in KOH. We tested the cathode in electrolyte-lean environments and found a drastic improvement in cycling stability in NaOH. The cathode exhibited higher initial capacity in lean amounts of KOH, but capacity retention plummeted after the first 20 cycles. In contrast, the cathode in NaOH delivered 65% of the theoretical capacity for over 400 cycles.
Yuantai He et al 2024 J. Electrochem. Soc. 171 030531
The magnesium ion batteries are gaining huge attention in the field of battery energy due to high energy density, low cost potential and high safety performance. So far, the research of magnesium ion batteries has been slow. The surface and structural properties of cathode electrode materials greatly limiting the discharge performance of magnesium ion battery. Herein, a facile synthesis of Cu2S nano-hollow spheres for high performance magnesium ion battery cathode electrode materials was reported. This nano-hollow spheres have a large specific surface area (12.84 m2 g−1) which can reduce the volume expansion caused by magnesium ions during embedding and detachment, and facilitate ion diffusion during the discharge-charging process. Consequently, the nano-hollow porous Cu2S deliver a 152 mAh g−1 after 850 cycles at 560 mA g−1 hold a long-term cycling stability as cathode materials for magnesium ion battery. This work not only demonstrates the great potential of NHP-Cu2S materials, for application in magnesium ion batteries, but also sheds a new light on the application of metal sulfides in magnesium ion batteries.
Youngju Lee and Peng Bai 2024 J. Electrochem. Soc. 171 030530
While the onset of dendrites found inside solid polymer electrolytes was typically analyzed by the dilute solution theory, nonideal behaviors such as dendrites at underlimiting current densities were often reported. Here, we consider two critical factors that were often neglected in existing studies, the severe heterogeneous current distribution and the dynamic change of modulus during the polarization process. Polymers with different dynamic mechanical properties were assessed, exploiting the recently discovered mechanism of phase transformation inside low-salt-concentration polymers. Analyses of the operando images revealed two characteristic points on the potential curve, the local and total concentration depletion which each corresponded to the starting and stopping point of dendrites. We further assess these dynamics at different degrees of heterogeneity controlled by different electrode sizes. The penetration dynamics and Sand's time scaling exponent were heavily affected by both the initial concentration and the electrode size, which stress the significance of interfacial dynamic heterogeneity in working batteries.
Aoife Carroll et al 2024 J. Electrochem. Soc. 171 030529
Highly ordered three-dimensionally structured carbon inverse opals (IOs) produced from sucrose are stable electrodes in sodium-ion and potassium-ion batteries. The walls of the ordered porous carbon structure contain short-range graphitic areas. The interconnected open-worked structure defines a conductive macroporous monolithic electrode that is easily wetted by electrolytes for Na-ion and K-ion systems. Electrochemical characterization in half-cells against Na metal electrodes reveals stable discharge capacities of 25 mAh g−1 at 35 mA g−1 and 40 mAh g−1 at 75 mA g−1 and 185 mA g−1. In K-ion half cells, the carbon IO delivers capacities of 32 mAh g−1 at 35 mA g−1 and ∼25 mAh g−1 at 75 mA g−1 and 185 mA g−1. The IOs demonstrate storage mechanisms involving both capacitive and diffusion-controlled processes. Comparison with non-templated carbon thin films highlights the superior capacity retention (72% for IO vs 58% for thin film) and cycling stability of the IO structure in Na-ion cells. Robust structural integrity against volume changes with larger ionic radius of potassium ions is maintained after 250 cycles in K-ion cells. The carbon IOs exhibit stable coulombic efficiency (>99%) in sodium-ion batteries and better coulombic efficiency during cycling compared to typical graphitic carbons.
Review articles
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Ali Asghar et al 2024 J. Electrochem. Soc. 171 030526
Supercapacitors (SCs) are gaining popularity as energy storage devices (ESDs), and their electrode materials strongly influence their performance. There is no doubt that SCs are capable and reliable ESDs for producing high power even when they operate at low energy levels. However, highly efficient electrode materials are still required to make the SC an effective choice for ESD. The surface modification of the electrode materials can improve the power and energy density of materials, which is beneficial for enhancing the electrochemical performance of the SC. During the past few years, more research has been reported to develop new electrode materials for improving SCs' energy density, charge retention, specific capacitance, stability, and rate performance. This review focuses on the execution of progressive organic-based electrode materials called metal-organic frameworks (MOFs) in the SC. The main purpose of this review is to explain the MOFs-based electrode materials and their progress in the field of SC. MOFs are advanced materials for supercapacitors because they allow for various features, including dimensions. They offer high stability, high capacity, adjustable pore size, greater aspect ratios, larger surface areas, and stronger bonding between metal and organic linkers than the previously reported electrode materials (Metal oxide, sulfide, phosphate, etc). These properties of MOFs-based electrode materials make them promising for electrochemical energy storage applications. Finally, the challenges and perspectives of MOFs-based electrode materials are discussed.
Beibei Hu et al 2024 J. Electrochem. Soc. 171 037523
Colorectal cancer is a common tumor that kills tens of thousands of people each year. Colorectal cancer was divided into two groups: primary colorectal cancer and metastatic colorectal cancer, the latter of which requires complicated treatment. The methods of early diagnosis of colorectal cancer include colorectal laparoscopy, tissue section, and B-ultrasonography. Although these methods produce desirable results, the pain of the process is limited by the need for professional instruction. As more and more biomarkers for colorectal cancer are being discovered, electrochemistry has received a lot of attention due to its advantages of being cost-effective, non-invasive, and highly sensitive. Colorectal cancer biomarkers are divided into nucleic acid, protein, and metabolite three categories, of which protein biomarkers are the most common. There are CEA, CA153, CA199, AFP, IL-6, CDH-17, IL-13Rα2, E-Cadherin, FGFR4, etc. This paper reviews various electrochemical platforms for biomarker detection of colorectal cancer. This review will pave the way for the establishment of new electrochemical platforms for screening various colorectal cancer biomarkers.
Highlight
Various markers and their application in the treatment and diagnosis of colorectal cancer were reviewed
According to different electrochemical platforms, the detection of various markers was summarized
It is hoped that this review will guide the construction of more colorectal cancer-related biosensors
Anjali Tripathi et al 2024 J. Electrochem. Soc. 171 037520
The fields of biosensing have been transformed by the discovery of extraordinary molecular recognition components, such as aptamers and biomimetic receptors. Systematic Evolution of Ligands by Exponential Enrichment (SELEX) is a method used to select aptamers, or short sequences of single-stranded DNA (ssDNA) or RNA (ssRNA), based on their unique binding affinity to target molecules. Molecularly imprinted polymers (MIPs) are a type of biomimetic receptor that mimics the selectivity of natural receptors inside a synthetic matrix. They make it possible to identify pathogens, and illness biomarkers with accuracy. Aptamers and biomimetic receptors play crucial roles in various fields including diagnostics, therapeutics, and biosensing. Their high specificity, versatility, and adaptability enable targeted detection, drug delivery, and biomolecule manipulation, thereby contributing to advancements in personalized medicine, biotechnology, and disease diagnosis. Aptamers and biomimetic receptors have been combined with cutting-edge technologies, like nanotechnology and lab-on-a-chip systems, to create biosensors that are quick, portable, and extremely sensitive. These recognition features are anticipated to become more important as technology develops, helping to address global issues, advance biosensing capabilities, and raise people's standard of living everywhere. Recent advancements and innovation on Aptamers and Biomimetic Receptors in Biosensing have been discussed in this review article.
Shirsendu Mitra et al 2024 J. Electrochem. Soc. 171 037511
Micro/-nano motors (MNMs) are deployed to perform cutting edge research and development activities that include biomedical engineering, environment monitoring, energy harvesting and more. MNMs progressively strives for miniaturization of MNMs, mightier self-propulsion, precision of motion, and smarter motion control. The last decade published several reports on biosensing applications of MNMs targeting enhanced specificity, selectivity. Among MNM mediated biosensors, the electrochemical biosensor is the most important stake holder. Motion of MNMs enable active transport, augmented reaction kinetics, and better selectivity causing smarter biosensing. This review article explores the most advanced development of electrochemical biosensing deploying MNMs that took place in recent past. Briefly, this article covers chronological development in the field of MNM mediated electrochemical biosensing with emphasis on, conventional working electrode based sensing, DNA walker modificaitons, MNM based real time electrochemical signal monitoring, and scope of MNM mediated electrochemical sensing for intracellular monitoring or drug delivery. Conclusively, the review considers the most recent development in the field of MNM mediated electrochemical sensing that includes both in vitro and in vivo electrochemical biosensing. Additionally, we discuss use of electorchemical redox reactions for imparting motion to the MNMs in physiological fluids for intracellular manipulation, targeted drug delivery, and more.
Ruijing Kong et al 2024 J. Electrochem. Soc. 171 032504
Molten salts play an important role in the electrolysis of solid metal compounds, especially oxides and sulfides, and have an impressive storage capacity and power, so they are now the electrolyte for many new types of rechargeable batteries. Unfortunately, due to the high viscosity and high surface tension of molten salt, the unsatisfactory wettability of electrode and molten salt restricts the development of molten salt electrochemistry. In the past half century, the research on interface phenomena has been devoted to establishing more accurate models for measuring surface tension and wetting angle, developing more scientific wetting angle measurement techniques, and exploring the influencing factors of wettability. Different from water solution interface, molten salt experiment is in high temperature and pressure environment, so it is difficult to test the wetting angle, and there are few researches on the interface phenomenon of molten salt. In this paper, on the basis of existing models and experimental data, the factors and mechanisms that lead to the difference of wettability between melt and solid matrix in molten salt systems are analyzed in detail. Finally, we put forward the prospects and suggestions for the study of the wettability of melt to solid substrate in molten salt.
Highlights
The research status of electrode wettability in molten salt is reviewed systematically, and the measuring method and mechanism of high-temperature interface wettability are introduced briefly.
To propose a priority scheme to improve the wettability of electrodes, the factors affecting the wettability of electrodes in molten salt were summarized and discussed in detail.
We put forward the prospects and suggestions for the study of the wettability of electrodes in molten salt.
Editor's Choice
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S. Yanev et al 2024 J. Electrochem. Soc. 171 020512
Li-In electrodes are widely applied as counter electrodes in fundamental research on Li-metal all-solid-state batteries. It is commonly assumed that the Li-In anode is not rate limiting, i.e. the measurement results are expected to be representative of the investigated electrode of interest. However, this assumption is rarely verified, and some counterexamples were recently demonstrated in literature. Herein, we fabricate Li-In anodes in three different ways and systematically evaluate the electrochemical properties in two- and three-electrode half-cells. The most common method of pressing Li and In metal sheets together during cell assembly resulted in poor homogeneity and low rate performance, which may result in data misinterpretation when applied for investigations on cathodic phenomena. The formation of a Li-poor region on the separator side of the anode is identified as a major kinetic bottleneck. An alternative fabrication of a Li-In powder anode resulted in no kinetic benefits. In contrast, preparing a composite from Li-In powder and sulfide electrolyte powder alleviated the kinetic limitation, resulted in superior rate performance, and minimized the impedance. The results emphasize the need to fabricate optimized Li-In anodes to ensure suitability as a counter electrode in solid-state cells.
Highlights
The fabrication of Li-In anodes needs to be optimized to ensure suitability as a counter electrode in sulfide all-solid-state batteries.
The Li-In counter electrode may often be the limiting factor of sulfide all-solid-state halfcells.
Pressing Li and In foil together results in a kinetically limited anode.
Composites from Li-In and sulfide electrolyte result in stable reference potential, superior rate performance and low impedance of the counter electrode.
Ramver Singh et al 2024 J. Electrochem. Soc. 171 013501
Electrical discharge micromachining (EDM) poses challenges to the fatigue-life performance of machined surfaces due to thermal damage, including recast layers, heat-affected zones, residual stress, micro-cracks, and pores. Existing literature proposes various ex situ post-processing techniques to mitigate these effects, albeit requiring separate facilities, leading to increased time and costs. This research involves an in situ sequential electrochemical post-processing (ECPP) technique to enhance the quality of EDMed micro-holes on titanium. The study develops an understanding of the evolution of overcutting during ECPP, conducting unique experiments that involve adjusting the initial radial interelectrode gap (utilizing in situ wire-electrical discharge grinding) and applied voltage. Additionally, an experimentally validated transient finite element method (FEM) model is developed, incorporating the passive film formation phenomenon for improved accuracy. Compared to EDM alone, the sequential EDM-ECPP approach produced micro-holes with superior surface integrity and form accuracy, completely eliminating thermal damage. Notably, surface roughness (Sa) was reduced by 80% after the ECPP. Increasing the voltage from 8 to 16 V or decreasing the gap from 60 to 20 μm rendered a larger overcut. This research's novelty lies in using a two-phase dielectric (water-air), effectively addressing dielectric and electrolyte cross-contamination issues, rendering it suitable for commercial applications.
Highlights
Better micro-hole quality through in situ sequential eco-friendly near-dry EDM & ECM
Successfully resolved dielectric-electrolyte cross-contamination in sequential processes
Unique experiments that adjust the initial radial IEG using in situ wire-EDG
Developed and validated a transient FEM model, incorporating passivation aspect
Achieved recast layer-free holes with Sa values approximately 80% lower than EDM holes
Yuefan Ji and Daniel T. Schwartz 2023 J. Electrochem. Soc. 170 123511
Analytical theory for second harmonic nonlinear electrochemical impedance spectroscopy (2nd-NLEIS) of planar and porous electrodes is developed for interfaces governed by Butler-Volmer kinetics, a Helmholtz (mainly) or Gouy-Chapman (introduced) double layer, and transport by ion migration and diffusion. A continuum of analytical EIS and 2nd-NLEIS models is presented, from nonlinear Randles circuits with or without diffusion impedances to nonlinear macrohomogeneous porous electrode theory that is shown to be analogous to a nonlinear transmission-line model. EIS and 2nd-NLEIS for planar electrodes share classic charge transfer RC and diffusion time-scales, whereas porous electrode EIS and 2nd-NLEIS share three characteristic time constants. In both cases, the magnitude of 2nd-NLEIS is proportional to nonlinear charge transfer asymmetry and thermodynamic curvature parameters. The phase behavior of 2nd-NLEIS is more complex and model-sensitive than in EIS, with half-cell NLEIS spectra potentially traversing all four quadrants of a Nyquist plot. We explore the power of simultaneously analyzing the linear EIS and 2nd-NLEIS spectra for two-electrode configurations, where the full-cell linear EIS signal arises from the sum of the half-cell spectra, while the 2nd-NLEIS signal arises from their difference.
Leonardo I. Astudillo and Hubert A. Gasteiger 2023 J. Electrochem. Soc. 170 124512
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 H2/N2 (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 VRHE at 80 °C and 30%-100% RH under either H2/N2 or H2/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 H2/O2 and H2/Air performance at 80 °C/100% RH were monitored. While the ECSA loss decreases with decreasing RH, it is independent of the gas feeds. Furthermore, the H2/Air performance loss only depends on the ECSA loss. ASTs under H2/N2 versus H2/Air only differ with regards to the chemical/mechanical degradation of the membrane.
Evans Leshinka Molel and Thomas F. Fuller 2023 J. Electrochem. Soc. 170 103501
Mathematical models of electrochemical systems are useful to refine our understanding of systems containing complex, coupled phenomena, to design and control electrochemical devices, and to help novices in developing intuition for the behavior of electrochemical systems. Regardless of the application, elucidating the relationship between current and potential is central to understanding how electrochemical systems behave. Here, we report on historical and future perspectives of simulating electrochemical systems with open-source, python-based tools. FEniCSx, a popular open-source computing platform for solving partial differential equations, is applied to the solution of primary and secondary current distributions for two- and three- dimensional geometries. FEniCSx is used on both desktop computers as well as within high performance computing environments, such as Georgia Tech's PACE. Simulations are known to increase interactions between instructors and students, and to help students visualize content. Recently, python tools have been applied to simple electrochemical systems. Because of the low barrier to entry and access to numerous computational packages, the Anaconda distribution of python is promoted. A series of dynamic simulations are designed to help students improve their understanding of electrochemical systems. These simulations feature animation and use of widgets that allow students to adjust parameters and immediately observe the results.
Accepted manuscripts
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Gallawa et al
Tin antimonide (SnSb) is a promising alloying anode for sodium-ion batteries due to its high theoretical capacity and relative stability. The material is popular in the battery field, but, to our knowledge, few studies have been conducted on the influence of altering Sn and Sb stoichiometry on anode capacity retention and efficiency over time. Here, Sn-Sb electrodes were synthesized with compositional control by optimizing electrodeposition parameters and stoichiometry in solution and the alloys were cycled in sodium-ion half-cells to investigate the effects of stoichiometry on both performance and electrochemical phenomena. Higher concentrations of antimony deposited into the films were found to best maintain specific capacity over 270 cycles in the tin-antimony alloys, with each cell showing a slow, gradual decrease in capacity. We identified that a 1:3 ratio of Sn:Sb retained a specific capacity of 486 mAh/g after 270 cycles, highlighting a need to explore this material further. These results demonstrate how control over stoichiometry in Sn-Sb electrodes is a viable method for tuning performance.
Fell et al
The library of redox-active organics that are potential candidates for electrochemical energy storage in flow batteries is exceedingly vast, necessitating high-throughput characterization of molecular lifetimes. Demonstrated extremely stable chemistries require accurate yet rapid cell cycling tests, a demand often frustrated by time-denominated capacity fade mechanisms. We have developed a high-throughput setup for elevated temperature cycling of redox flow batteries, providing a new dimension in characterization parameter space to explore. We utilize it to evaluate capacity fade rates of aqueous redox-active organic molecules, as functions of temperature. We demonstrate Arrhenius-like behaviour in the temporal capacity fade rates of multiple flow battery electrolytes, permitting extrapolation to lower operating temperatures. Collectively, these results highlight the importance of accelerated decomposition protocols to expedite the screening process of candidate molecules for long lifetime flow batteries.
Fenske et al
Prelithiation is widely recognized as a promising technology to enable the use of high capacity anode active materials such as silicon. Numerous prelithiation techniques have been proposed over the years, with a handful successfully undergoing pilot scale testing. Nevertheless, new challenges arise when moving from optimizing single processes to integrating them into the process chain. A major concern is the stability of prelithiated electrodes against moisture. In this study, we investigated the influence of industrially-relevant moisture levels on the electrochemical performance of prelithiated graphite/SiOx composite anodes in 3-electrode half- and full-cells. We identify several indicators of electrode degradation such as an increase in open circuit potential, a decrease in graphite lithiation potential, and changes in specific charge/discharge capacity. The underlying degradation mechanisms are investigated using electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry, which show increased solid electrolyte interphase (SEI)-related interfacial resistances but no clear evidence of SEI degradation. Based on the experimental results, we define a process window for the stability of the investigated electrodes as a function of dew point and exposure time. Our results indicate an encouragingly high stability at dew points up to -40°C for a realistic exposure time of 1 hour
Nagy et al
We report on the construction and investigation of Li–air batteries consisting of a charcoal cathode and cotton texture soaked with different organic solvents containing a lithium triflate (LiOTf) electrolyte. Charcoal was found to be an appropriate cathode for Li–air batteries. Furthermore, cycling tests showed stable operation at over 800 cycles when dimethyl sulfoxide (DMSO) and diethylene glycol dimethyl ether (DEGME) were used as solvents, whereas low electrochemical stability was observed when propylene carbonate was used. The charging, discharging, and long-term discharging steps were mathematically modeled. Electrochemical impedance spectroscopy showed Gerischer impedance, suggesting intensive oxygen transport at the surface of the charcoal cathode. Diffusion, charge transfer, and solid electrolyte interphase processes were identified using distribution of relaxation time analysis. In the polypropylene (PP) membrane soaked with LiOTf in DEGME, three different states of Li ions were identified by 7Li-triple-quantum time proportional phase increment nuclear magnetic resonance measurements. On the basis of the latter results, a mechanism was suggested for Li-ion transport inside the PP membrane. The activity of the charcoal cathode was confirmed by Raman and cyclic voltammetry measurements.
Cheng et al
Composite polymer electrolytes composed of inorganic fillers and organic polymers are promising electrolyte candidates for Li metal batteries, with benefits of improved safety and suppressed lithium dendrite growth. However, a severe concentration polarization effect often occurs when using conventional dual-ion polymer electrolytes, and the increase in internal impedance during cycling results in decreased lifespan of the battery. To address this challenge, a plasticized single-ion conducting composite polymer electrolyte (SICE) was designed and fabricated by polymerizing the monomers of lithium (4-styrenesulfonyl) (trifluoromethanesulfonyl) imide (LiSTFSI) and poly(ethylene glycol) methyl ether acrylate (PEGMEA), crosslinker poly(ethylene glycol) diacrylate (PEGDA), silane-modified Li6.28La3Al0.24Zr2O12 nanofibers (s@LLAZO NFs), along with PEG-based plasticizer tetraethylene glycol dimethyl ether (TEGDME), by heat-initiation. The anions were restrained and delocalized so that only Li cation migration occurred during the charging/discharging process, leading to a superior lithium-ion transference number. The s@LLAZO NFs enabled direct monomer grafting with the polymer matrix, resulting in controlled formation of an organic-inorganic network with increased filler content and improved filler distribution in the SICE system. The SICE membrane exhibited high ionic conductivity at room temperature, reduced activation energy and excellent oxidation stability. Most importantly, the all-solid-state Li-metal batteries assembled with the fabricated SICE demonstrated stable long-term cycling performance and
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Katrina Ramirez-Meyers et al 2024 J. Electrochem. Soc. 171 030524
MnO2, in its many phases, is abundant, non-flammable, non-toxic, reliable, made with abundant materials using simple manufacturing methods, and can have a high theoretical capacity for some phases (up to 617 mAh g−1). Here we have investigated the sensitivity of the performance ofbirnessite—produced in situ—to the presence of Bi2O3, depth-of-discharge, electrolyte salt type, and relative electrolyte volume. We prepared cathodes composed of 45 wt% MnO2, 22.5 wt% Bi2O3, and 22.5 wt% carbon additives, and compared cycling stability in two electrolytes—6.6 M KOH (27 wt%) and 6.6 M NaOH (21 wt%), and two types of 3-electrode test fixtures (flooded beaker or electrolyte-lean T-cell). Our results showed that birnessite can be synthesized electrochemically in NaOH, and cycling the cathode in NaOH improves its stability when compared to cycling in KOH. We tested the cathode in electrolyte-lean environments and found a drastic improvement in cycling stability in NaOH. The cathode exhibited higher initial capacity in lean amounts of KOH, but capacity retention plummeted after the first 20 cycles. In contrast, the cathode in NaOH delivered 65% of the theoretical capacity for over 400 cycles.
Youngju Lee and Peng Bai 2024 J. Electrochem. Soc. 171 030530
While the onset of dendrites found inside solid polymer electrolytes was typically analyzed by the dilute solution theory, nonideal behaviors such as dendrites at underlimiting current densities were often reported. Here, we consider two critical factors that were often neglected in existing studies, the severe heterogeneous current distribution and the dynamic change of modulus during the polarization process. Polymers with different dynamic mechanical properties were assessed, exploiting the recently discovered mechanism of phase transformation inside low-salt-concentration polymers. Analyses of the operando images revealed two characteristic points on the potential curve, the local and total concentration depletion which each corresponded to the starting and stopping point of dendrites. We further assess these dynamics at different degrees of heterogeneity controlled by different electrode sizes. The penetration dynamics and Sand’s time scaling exponent were heavily affected by both the initial concentration and the electrode size, which stress the significance of interfacial dynamic heterogeneity in working batteries.
Aoife Carroll et al 2024 J. Electrochem. Soc. 171 030529
Highly ordered three-dimensionally structured carbon inverse opals (IOs) produced from sucrose are stable electrodes in sodium-ion and potassium-ion batteries. The walls of the ordered porous carbon structure contain short-range graphitic areas. The interconnected open-worked structure defines a conductive macroporous monolithic electrode that is easily wetted by electrolytes for Na-ion and K-ion systems. Electrochemical characterization in half-cells against Na metal electrodes reveals stable discharge capacities of 25 mAh g−1 at 35 mA g−1 and 40 mAh g−1 at 75 mA g−1 and 185 mA g−1. In K-ion half cells, the carbon IO delivers capacities of 32 mAh g−1 at 35 mA g−1 and ∼25 mAh g−1 at 75 mA g−1 and 185 mA g−1. The IOs demonstrate storage mechanisms involving both capacitive and diffusion-controlled processes. Comparison with non-templated carbon thin films highlights the superior capacity retention (72% for IO vs 58% for thin film) and cycling stability of the IO structure in Na-ion cells. Robust structural integrity against volume changes with larger ionic radius of potassium ions is maintained after 250 cycles in K-ion cells. The carbon IOs exhibit stable coulombic efficiency (>99%) in sodium-ion batteries and better coulombic efficiency during cycling compared to typical graphitic carbons.
Dawei Xia et al 2024 J. Electrochem. Soc. 171 030528
Earth-abundant, cost-effective electrode materials are essential for sustainable rechargeable batteries and global decarbonization. Manganese dioxide (MnO2) and hard carbon both exhibit high structural and chemical tunability, making them excellent electrode candidates for batteries. Herein, we elucidate the impact of electrolytes on the cycling performance of commercial electrolytic manganese dioxide in Li chemistry. We leverage synchrotron X-ray analysis to discern the chemical state and local structural characteristics of Mn during cycling, as well as to quantify the Mn deposition on the counter electrode. By using an ether-based electrolyte instead of conventional carbonate electrolytes, we circumvent the formation of a surface Mn(II)-layer and Mn dissolution from LixMnO2. Consequently, we achieved an impressive ∼100% capacity retention for MnO2 after 300 cycles at C/3. To create a lithium metal-lean full cell, we introduce hard carbon as the anode which is compatible with ether-based electrolytes. Commercial hard carbon delivers a specific capacity of ∼230 mAh g−1 at 0.1 A g−1 without plateau, indicating a surface-adsorption mechanism. The resulting manganese dioxide||hard carbon full cell exhibits stable cycling and high Coulombic efficiency. Our research provides a promising solution to develop cost-effective, scalable, and safe energy storage solutions using widely available manganese oxide and hard carbon materials.
Eric Michael Fell et al 2024 J. Electrochem. Soc.
The library of redox-active organics that are potential candidates for electrochemical energy storage in flow batteries is exceedingly vast, necessitating high-throughput characterization of molecular lifetimes. Demonstrated extremely stable chemistries require accurate yet rapid cell cycling tests, a demand often frustrated by time-denominated capacity fade mechanisms. We have developed a high-throughput setup for elevated temperature cycling of redox flow batteries, providing a new dimension in characterization parameter space to explore. We utilize it to evaluate capacity fade rates of aqueous redox-active organic molecules, as functions of temperature. We demonstrate Arrhenius-like behaviour in the temporal capacity fade rates of multiple flow battery electrolytes, permitting extrapolation to lower operating temperatures. Collectively, these results highlight the importance of accelerated decomposition protocols to expedite the screening process of candidate molecules for long lifetime flow batteries.
Hans Fenske et al 2024 J. Electrochem. Soc.
Prelithiation is widely recognized as a promising technology to enable the use of high capacity anode active materials such as silicon. Numerous prelithiation techniques have been proposed over the years, with a handful successfully undergoing pilot scale testing. Nevertheless, new challenges arise when moving from optimizing single processes to integrating them into the process chain. A major concern is the stability of prelithiated electrodes against moisture. In this study, we investigated the influence of industrially-relevant moisture levels on the electrochemical performance of prelithiated graphite/SiOx composite anodes in 3-electrode half- and full-cells. We identify several indicators of electrode degradation such as an increase in open circuit potential, a decrease in graphite lithiation potential, and changes in specific charge/discharge capacity. The underlying degradation mechanisms are investigated using electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry, which show increased solid electrolyte interphase (SEI)-related interfacial resistances but no clear evidence of SEI degradation. Based on the experimental results, we define a process window for the stability of the investigated electrodes as a function of dew point and exposure time. Our results indicate an encouragingly high stability at dew points up to -40°C for a realistic exposure time of 1 hour
Lajos Nagy et al 2024 J. Electrochem. Soc.
We report on the construction and investigation of Li–air batteries consisting of a charcoal cathode and cotton texture soaked with different organic solvents containing a lithium triflate (LiOTf) electrolyte. Charcoal was found to be an appropriate cathode for Li–air batteries. Furthermore, cycling tests showed stable operation at over 800 cycles when dimethyl sulfoxide (DMSO) and diethylene glycol dimethyl ether (DEGME) were used as solvents, whereas low electrochemical stability was observed when propylene carbonate was used. The charging, discharging, and long-term discharging steps were mathematically modeled. Electrochemical impedance spectroscopy showed Gerischer impedance, suggesting intensive oxygen transport at the surface of the charcoal cathode. Diffusion, charge transfer, and solid electrolyte interphase processes were identified using distribution of relaxation time analysis. In the polypropylene (PP) membrane soaked with LiOTf in DEGME, three different states of Li ions were identified by 7Li-triple-quantum time proportional phase increment nuclear magnetic resonance measurements. On the basis of the latter results, a mechanism was suggested for Li-ion transport inside the PP membrane. The activity of the charcoal cathode was confirmed by Raman and cyclic voltammetry measurements.
Ortal Breuer et al 2024 J. Electrochem. Soc. 171 030510
One of the most powerful spectroscopic tools for battery analysis is X-ray photoelectron spectroscopy (XPS); however, its great power, must be accompanied by great responsibility for authenticity. Fluorine is documented to be unstable under XPS conditions, and fluorinated salts used in Li batteries show photodecomposition. As all-solid-state batteries advance, demand for surface characterization is increasing. Here, a popular solid polymer electrolyte comprising a fluorinated salt in a PEO matrix was measured by XPS. Rapid photodecomposition after few minutes produced mainly LiF, initially not found on the surface. Not being aware of such artifacts may lead to an erroneous analysis of the characterized electrochemical system.
Harrison J. Cassady et al 2024 J. Electrochem. Soc. 171 030527
A survey of 23 commercially available cation exchange membranes was performed for the downselection of membranes for use in a polysulfide-permanganate redox flow battery (pS-Mn RFB). The survey measured the flux of permanganate ions across a 0.1 mol L−1 concentration gradient as well as the membrane resistance in a 0.5 mol L−1 sodium chloride solution. The membranes exhibited the characteristic flux/resistance trade-off observed in most classes of membranes. To connect the individual membrane testing to how the membranes will perform in a device, cell performance data in a pS-Mn RFB was collected for three membranes from the survey. The coulombic, voltaic, and energy efficiency at low cycle counts aligned with the predictions from the membrane flux and resistance survey results. The study also identified three membranes—Fumapem F-930-RFS, Fumapem FS-715-RFS, and Aquivion E98-09S—that outperformed most other membranes regarding their position on the flux-resistance trade-off curve, indicating them to be good candidates for further testing.
Izaak Cohen et al 2024 J. Electrochem. Soc. 171 036507
In previous work, we introduced an elegant approach for bromide recovery from water by the introduction of a hybrid physical adsorption and capacitive deionization processes for selective removal and recovery of boron from water. In this paper, we show that the harsh environment of water contaminated with bromine-moieties adversely affects the longevity of relevant electrodes, with close to 100 consecutive work hours of bromides removal without noticeable degradation. To extend the lifespan of electrodes, we used an asymmetric CDI cell with a 1:5 positive/negative electrodes ratio in which a polarity switch between electrodes is applied every six adsorption-desorption cycles in a way that in each adsorption-desorption cycle, a different electrode of the six electrodes, functions as the positive electrode. We deduce that the polarity switch reduces oxidation and subsequent degradation of the positive electrodes, resulting in an extended lifecycle. After examining nine different carbonaceous materials, carbon cloth was chosen to be incorporated in the bromide- recovery cells because of its favorable kinetics and its physical and mechanical properties. We show that with a combination between endurance of the electrodes and asymmetric mode of operation, it is possible to overcome the main barrier that holds the technology from being practical.