Single-layer Cell Research Articles

Estimating the Values of the PDE Model Parameters of Rechargeable Lithium-Metal Battery Cells using Linear EIS

Abstract We introduce a partial-differential-equation model for rechargeable lithium-metal battery (LMB) cells whose parameter values are fully identifiable from cell-level experiments. From this model, we formulate a computationally tractable transfer-function (TF) model for use within optimization loops. A strategy is proposed for regressing the TF model to cell electrochemical impedance spectroscopy (EIS) measurements to estimate parameter values. We validate the regression using a synthetic dataset before application to a single-layer LMB pouch cell. The voltage RMSE between the fully identified model's predictions and laboratory measurements is about 4 mV for a GITT profile. We provide MATLAB code to simulate the model in COMSOL, compute cell impedance from the TF model, and perform model regression.

Current Collector Primers with Improved Physical and Electrochemical Properties

Lithium-ion batteries are the dominant technology for powering the growing markets of electric vehicles, consumer electronics, and grid storage. However, to meet the increasing demands for higher energy density, faster charging, lower cost, and longer cycle life, continued research of new materials and designs are required. One of the key components that affects the performance and durability of lithium-ion batteries is the current collector, which provides a conductive substrate for active materials. The interfacial conductivity, adhesion, and corrosion resistance of these foils is largely dictated by their native oxide surface layer. To improve any of these features, specialized primers may be applied prior to electrode manufacturing, presenting a unique electrode/active material interface. For instance, carbon-coatings may be applied to aluminum to improve the conductivity and adhesion of lithium iron phosphate (LFP) formulations. These carbon coatings are limited in their cost, thickness, and performance, particularly in next generation cell designs and application methods. PPG is exploring novel current collector coating technologies addressing the physical, electrochemical, and stability requirements of these chemistries and manufacturing process. In this presentation, we will elaborate on coatings development and the effect that novel primer layers have on mechanical properties and single-layer pouch cell cycle life.

Depletion of Electrolyte Salt Upon Calendaric Aging of Lithium-Ion Batteries and its Effect on Cell Performance

The trend for increased nickel content in layered transition metal oxide cathode active materials and increasing charging cut-off voltages aggravates aging of lithium-ion battery cells at high state of charge (SOC). We investigate the calendaric aging behavior of large-format automotive prototype cells and laboratory single-layer pouch cells at high but realistic cell voltages/SOCs and demonstrate that electrolyte oxidation in combination with follow-up reactions can cause a significant loss of the LiPF6 salt in the electrolyte. For this, we analyze the LiPF6 concentration in aged cells, the generation of H2 upon storage, and the cell resistance for different aging conditions. We show that the LiPF6 loss is a critical aging phenomenon, as it cannot readily be detected by capacity fading measurements at low/medium C-rates or by cell resistance measurements, while it severely reduces rate and fast-charging capability. Under certain circumstances, LiPF6 loss can even lead to a temporary capacity increase due to conversion of the conducting salt in the electrolyte to cyclable lithium in the active material. Finally, we suggest a possible reaction mechanism and a simple accounting model to keep track of how different side reactions involved in LiPF6 loss change the cyclable lithium inventory of a lithium-ion cell.

Entanglement Added to Cross-Linked Chains Enables Tough Gelatin-Based Hydrogel for Zn Metal Batteries.

Currently, it is still challenging to develop a hydrogel electrolyte matrix that can successfully achieve a harmonious combination of mechanical strength, ionic conductivity, and interfacial adaptability. Herein, a multi-networked hydrogel electrolyte with a high entanglement effect based on gelatin/oxidized dextran/methacrylic anhydride, denoted as ODGelMA is constructed. Attribute to the Schiff base network formulation of ─RC═N─, oxidized dextran integrated gelatin chains induce a dense hydrophilic conformation group. Furthermore, addition of methacrylic anhydride through a grafting process, the entangled hydrogel achieves impressive mechanical features (6.8MPa tensile strength) and high ionic conductivity (3.68mScm-1 at 20°C). The ODGelMA electrolyte regulates the zinc electrode by circumventing dendrite growth, and showcases an adaptable framework reservoir to accelerate the Zn2+ desolvation process. Benefiting from the entanglement effect, the Zn anode achieves an outstanding average Coulombic efficiency (CE) of 99.8% over 500 cycles and cycling stability of 900h at 5mAcm-2 and 2.5mAhcm-2. The Zn||I2 full cell yields an ultra-long cycling stability of 10000 cycles with a capacity retention of 92.4% at 5C. Furthermore, a 60mAh single-layer pouch cell maintains a stable work of 350 cycles.

Lithium Plating at the Cell Edge Induced by Anode Overhang during Cycling in Lithium-Ion Batteries: Part I. Modeling and Mechanism

The anode overhang is usually cited to prevent lithium plating at the cell edges of lithium-ion batteries. Still, numerous reports in the literature show lithium plating at the cell edge, which is typically referred to as edge plating. Edge plating is often attributed to inhomogeneous lithium distribution, thermal gradients, or pressure-dependent effects. This work presents an easy-to-implement two-dimensional electrochemical model demonstrating inhomogeneous lithiation induced by the anode overhang, which can explain experimentally observed edge plating. First, the mechanism of inhomogeneous lithiation due to the anode overhang is explained in detail. Then, a parameter study on charge protocol and geometric cell properties is presented, and the implications for cell applications are analyzed. Finally, the findings are discussed and put into a broader perspective of cell design, manufacturing, and fast charging application. In Part II of this work, the simulation is validated experimentally using multi-reference electrode single-layer pouch cells.

Enable superior performance of ultra-high loading electrodes through the cost-efficient solvent-free electrode manufacturing technology

This research explores an innovative solvent-free method for fabricating ultra-high loading NMC811 and graphite electrodes (∼6mAh∙cm−2), showcasing remarkable electrochemical performance enhancements compared to the electrodes prepared by the conventional slurry-casting method. The optimized microstructure with dry-printed (DP) electrodes enhanced electrolyte penetration and minimized lithium-ion diffusion tortuosity resulting in improved rate performance at high current rates. Additionally, this innovative electrode manufacturing approach enables more uniform CEI and SEI formation and growth, which effectively doubles the cycle life of single-layer pouch cells with DP electrodes. Beyond the performance enhancements, this method also offers a notable 29.2 % overall cost advantages, potentially revolutionizing future battery manufacturing. The findings presented in this work underscore the potential of solvent-free manufacturing technology as a high-loading capable and cost-efficient path for advanced battery production.

High-Loading Lithium-Sulfur Batteries with Solvent-Free Dry-Electrode Processing.

Lithium-sulfur (Li-S) batteries, with their high energy density, nontoxicity, and the natural abundance of sulfur, hold immense potential as the next-generation energy storage technology. To maximize the actual energy density of the Li-S batteries for practical applications, it is crucial to escalate the areal capacity of the sulfur cathode by fabricating an electrode with high sulfur loading. Herein, ultra-high sulfur loading (up to 12mgcm-2) cathodes are fabricated through an industrially viable and sustainable solvent-free dry-processing method that utilizes a polytetrafluoroethylene binder fibrillation. Due to its low porosity cathode architecture formed by the binder fibrillation process, the dry-processed electrodes exhibit a relatively lower initial capacity compared to the slurry-processed electrode. However, its mechanical stability is well maintained throughout the cycling without the formation of electrode cracking, demonstrating significantly superior cycling stability. Additionally, through the optimization of the dry-processing, a single-layer pouch cell with a loading of 9mgcm-2 and a novel multi-layer pouch cell that uses an aluminum mesh as its current collector with a total loading of 14mgcm-2 are introduced. To address the reduced initial capacity of dry-processed electrodes, strategies such as incorporating electrocatalysts or employing prelithiated active materials are suggested.

Design and mechanical properties analysis of a cellular Waterbomb origami structure

Cellular structures are commonly used to design energy-absorbing structures, and origami structures are becoming a prevalent method of cellular structure design. This paper proposes a foldable cellular structure based on the Waterbomb origami pattern. The geometrical configuration of this structure is described. Quasi-static compression tests of the origami tube cell of this cellular structure are conducted, and load-displacement relationship curves are obtained. Numerical simulations are carried out to analyze the effects of aspect ratio, folding angle, thickness and number of layers of origami tubes on initial peak force and specific energy absorption (SEA). Calculation formulas for initial peak force and SEA are obtained by the multiple linear regression method. The degree of influence of each parameter on the mechanical properties of the single-layer tube cell is compared. The results show that the cellular structure exhibits negative stiffness and periodic load-bearing capacity, as well as folding angle has the most significant effect on the load-bearing and energy-absorbing capacity. By adjusting the design parameters, the stiffness, load-bearing capacity and energy absorption capacity of this cellular structure can be adjusted, which shows the programmable mechanical properties of this cellular structure. The foldability and the smooth periodic load-bearing capacity give the structure potential for application as an energy-absorbing structure.

Autophagy Determines Distinct Cell Fates in Human Amnion and Chorion Cells.

Human fetal membranes (amniochorion) that line the intrauterine cavity consist of two distinct cell layers; single-layer amnion epithelial cells (AEC) and multilayer chorion trophoblast cells (CTC). These layers are connected through a collagen-rich extracellular matrix. Cellular remodeling helps support membrane growth and integrity during gestation and helps to maintain pregnancy. Preterm prelabor rupture of the human amniochorionic (fetal) membrane (pPROM) is antecedent to 40% of all spontaneous preterm birth. Oxidative stress (OS) induced activation of the p38 MAPK due to various maternal risk exposures and the amniochorion cells' senescence are reported pathological features of pPROM. Our transcriptomics analysis implicated dysregulated autophagy and epithelial-mesenchymal transition (EMT) in fetal membranes from pPROM. The molecular interplay between OS-induced p38 MAPK activation, autophagy, and EMT was investigated in AECs and CTCs to better understand the involvement of autophagy and EMT. We report the differential impact of OS on the autophagic machinery in AECs and CTCs, resulting in distinct cell fates. In AECs, OS-induced p38 MAPK activation causes autophagosome accumulation and reduced autophagic flux mediated by decreased ULK1 activity and kinase activity, leading to senescence. In CTCs, induction of autophagy has a limited effect; however, inhibition of autophagy led to SQSTM1-mediated EMT of trophoblast cells. Autophagy, EMT, and senescence were associated with proinflammatory changes. Thus, AECs and CTCs respond differently to OS via differential autophagy response, partly mediated via p38 MAPK. Besides senescence, OS-induced autophagy dysregulation in amniochorion cells may play a mechanistic role in pPROM pathophysiology.

Aging Mechanism For Calendar Aging of Li-Ion Cells With Si/Graphite Anodes

Calendar aging of Li-ion batteries with Si/graphite electrodes was investigated within this study. A total of 121 single-layer pouch full cells with either graphite or Si/graphite (3.0 wt−%, 5.8 wt−% and 20.8 wt−% Si) anodes and NMC622 cathodes with the same N/P ratio were built on pilot-scale. Calendar aging was studied at SoC 30%, 60%, and 100%, as well as temperature (25 °C, 45 °C, 60 °C) and time dependence. The aging data was analyzed in terms of capacity fade and a square-root behavior was observed. Differential voltage analysis (DVA) has been performed as a function of aging time. The observed temperature and time dependence is best described by time dependent, 3D Arrhenius plots. Post-Mortem analysis (SEM, EDX, GD-OES) is applied to investigate the changes on electrode and material level. Conclusions are drawn on the main aging mechanisms for calendar aging of Li-ion cells with Si/graphite anodes and differences between Si/graphite and pure graphite anodes are discussed. The Si-containing cells show a combination of lithium inventory loss and a loss of accessible Si active material, both caused by SEI growth.

Temperature Self-Adaptive and Color-Adjustable Smart Window Based on Templated Cholesteric Liquid Crystals.

Cholesteric liquid crystals (CLCs) exhibit selective reflection due to their self-assembled helical superstructures. Reconfigurable templates can achieve integration functions via inducing processes of molecular assemblies. Here we demonstrate temperature self-adaptive and color-adjustable smart windows using CLCs, which are fabricated via the templating method and exhibit simultaneous reflections in the visible and infrared spectra. Reflection bands formed by the refilled CLC materials can be adjusted reversibly both upon thermal and electrical actuation. In CLC with adjustable reflection in the infrared, the central wavelength of the infrared reflection band can be adjusted from 950 nm to 1305 nm via temperature, and from 1150 nm to 950 nm via electric field. A temperature variation of 10.3 °C within 55 s was induced by the single-layer templated CLC cell, and a comfortable temperature range could be effectively maintained by the CLC cell in a varied environment. In CLC with dynamic color in the visible spectrum, color shifts from 530 nm to 650 nm tuned by temperature and from 530 nm to 440 nm adjusted by electric field were obtained. Temperature-responsive reflection in the infrared spectrum contributes to automatic thermal management, and electric-field-induced band shift in the visible spectrum enables active dynamic color adjustment. The presented templated CLC smart windows show considerable potential in energy conservation and biological clock regulation fields.

How to Make a Single-Layer Pouch Cell That Matches the Performance of a Commercial Li-Ion Cell

As lithium-ion batteries (LIBs) have exploded in popularity due to the consumer electronics and electric vehicle industries, many resources are poured into research. While the simplest cell format requiring the least amount of active material to make in a research laboratory to study various aspects of the cell is usually the coin cell, it is far from the most representative of commercial LIBs. Oftentimes, coin cells are made with a large negative electrode overhang to reduce the risk from positive/negative electrode misalignment, but the overhang region can cause Li+ to become effectively trapped at higher C-rates1. While this is a necessary trade-off in today’s commercial LIB manufacturing, the overhang area is normally a much smaller fraction of the total negative electrode area in a commercial cell than in a laboratory coin cell, which can lead to discrepancies in cycle testing. Moreover, during assembly of commercial stacked or wound cells, there is always a region in which one side of a double-sided coating, typically the negative, is not needed and thus a single-sided electrode should be used. However, not all manufacturers eliminate the outward-facing second side and elect to simply use double-sided coatings throughout. Therefore, studying the effects of excess electrode in single-layer pouch cells will be explored in this presentation. In this presentation, cells made in various formats (coin and stacked pouch) will be compared to single-layer pouch cells made with and without negative electrode overhang. Single-layer pouch cells are the easiest format for assembling full cells without overhang because they are neither too small nor too big for positive/negative electrode alignment to be difficult. Moreover, single-layer pouch cells made with double-sided coatings (without overhang) and cycled using Ultra-High Precision Coulometry (UHPC) will be shown to have poor cycling. This is for two reasons: 1) for a double-sided negative, the outward-facing coating of the electrode can trap Li+ just like the overhang on the inward-facing coating; and 2) the outward-facing positive can be deintercalated and provide more capacity than desired2, possibly even surpassing the negative/positive areal capacity ratio. Single-layer pouch cells with no overhang are shown in Figure 1a to outperform all other cell formats tested, retaining 90% of their original capacity after 500 cycles at C/3 and 40 °C, and have the lowest difference in capacity between typical C/3 and C/20 checkup cycles as shown in Figure 1b. The stacked pouch cells in Figure 1 are composed of 3 positive and 4 negative electrodes that are all double-sided, meaning there are two outward-facing negative electrode coatings that can trap Li+, possibly resulting in the much poorer capacity fade to 80% after 500 cycles illustrated in Figure 1a. Thus, single-layer pouch cells without overhang give the most realistic cycling results for the tested electrode materials. Figure 1. C/3 cycling of full cells of various formats denoted in the legend. Plotted in (a) is the normalized discharge capacity and (b) is the difference in areal discharge capacity between the C/20 checkup cycle and preceding C/3 cycle. REFERENCES Gyenes, B., Stevens, D.A., Chevrier, V.L., and Dahn, J.R. (2015). Understanding Anomalous Behavior in Coulombic Efficiency Measurements on Li-Ion Batteries. J Electrochem Soc 162, A278–A283. 10.1149/2.0191503jes.Smith, A., Stüble, P., Leuthner, L., Hofmann, A., Jeschull, F., and Mereacre, L. (2023). Potential and Limitations of Research Battery Cell Types for Electrochemical Data Acquisition. Batter Supercaps e202300080. doi.org/10.1002/batt.202300080. Figure 1

Temperature Dependent Discharge Rate Tests and Cycling Stability of High-Nickel Ncm Cathodes Employing a µ-Reference Electrode in All-Solid-State Pouch Cells

All-solid-state batteries (ASSBs) are widely investigated in the field of lithium-ion battery (LIB) research, since they might offer several advantages over the conventional LIB technology based on liquid electrolytes, for example a possible lower flammability of solid electrolytes compared to organic solvents in LIBs.[1] However, Li6PS5Cl (LPSCl), a commonly used sulfidic solid electrolyte undergoes exothermic reactions with de-lithiated nickel-rich NCM already above 150°C.[2] Establishing a temperature window for save long-term operation is therefore required for large-scale applications in, e.g., battery electric vehicles.Additionally, a fundamental challenge for the development and electrochemical characterization of individual electrodes for ASSBs is to achieve accurate potential control of the working electrode (WE). In general, this can be done by either the use of a reference electrode (RE) or, alternatively, by the use of a counter electrode (CE) with a well-defined constant potential and little overpotential, whereby the later condition is difficult to meet at high C-rates for electrodes with industrially relevant areal capacities. Recently, we reported on a single-layer pouch cell configuration with an integrated µ-RE, which consist of a thin (~50 µm Ø) in-situ lithiated gold wire that provides a long-term stable reference potential.[3] This configuration was adapted from a µ-RE based three-electrode setup for liquid electrolyte LIBs.[4] In this study, we utilize the described setup to investigate the temperature dependent rate capability and cycling stability of ASSB cathodes, composed of a LiNi0.85Co0.10Mn0.05O2, solid electrolyte (LPSCl), conductive carbon additive, and a binder in sulfidic ASSB single-layer pouch cells at a comparatively low measurement pressure of 30 MPa. Besides the NCM WE with an application-oriented areal capacity of 3 mAh/cm2, a sulfidic solid electrolyte sheet-type separator,[5] and an InLi alloy counter electrode are used. In the cathode discharge rate tests, the upper and lower cathode cutoff potentials are controlled via the lithiated gold wire µ-RE. Stepwise increased current densities from 0.1C up to 10C (30 mA/cm²) are investigated, while the charge rate is kept constant at 0.2C (CCCV).Figure 1 exemplarily shows the discharge rate data obtained at 25°C for upper/lower cathode cutoff potentials of 2.6/4.2 V vs. Li+/Li, demonstrating a specific capacity of ~180 mAh/gCAM at 0.1C, which decreases by only ~15% when increasing the discharge rate to 1C. To the best of our knowledge, the here demonstrated rate capability is quite remarkable for cathodes with such high areal capacities. The deconvolution of the half-cell potentials shows that the InLi CE has a constant overpotential of ~400 mV at the highest here examined current density of 30 mA/cm2 (at 10C) and is therefore not interfering with the cathode discharge rate test. In our presentation we will discuss the temperature dependence of the discharge rate capability as well the temperature dependent cycling stability at a discharge rate of 1.0C, including intermittent rate tests. Acknowledgements: BASF (Ludwigshafen, Germany) is gratefully acknowledged for supplying the NCM material. Literature: [1]S. Hess, M. Wohlfahrt-Mehrens, M. Wachtler,J. Electrochem. Soc., 2015, 162 (2) A3084-A3097[2] T. Kim, K. Kim, S. Lee, G. Song, M. S. Jung, K. T. Lee, Chem. Mater., 2022, 34, 9159−9171[3] C. Sedlmeier, R. Schuster, C. Schramm, H.A.Gasteiger, J. Electrochem. Soc., 2023, 170, 030536[4]S. Solchenbach, D. Pritzl, E. J. Y. Kong, J. Landesfeind, H. A. Gasteiger,J. Electrochem. Soc., 2016, 163(10) A2265-A2272[5] C. Sedlmeier, T. Kutsch, R. Schuster, L. Hartmann, R. Bublitz, M. Tominac, M. Bohn, H. A. Gasteiger. J. Electrochem. Soc., 2022, 169, 070508 Figure 1

Design and Fabrication of Protonic Ceramic Fuel Cells Based on BaZr0.8Y0.2O3−δ |BaZr0.1Ce0.7Y0.1Yb0.1O3−δ Bilayer Electrolyte

Reducing electronic leakage is important for improving the performance of protonic ceramic fuel cells (PCFCs) because it can considerably decrease power efficiency. In this work, we explore the efficacy of bilayer electrolytes using BaZr0.8Y0.2O3−δ (BZY) and BaZr0.1Ce0.7Y0.1Yb0.1O3−δ (BZCYYb) as the anode and cathode-side electrolytes, respectively. Theoretical calculations were used to guide the design and experimental fabrication of highly efficient cells. Computational results showed that higher efficiencies were achieved when a thin BZY layer was applied to a thicker BZCYYb layer. This configuration served as a barrier, effectively preventing electronic leakage. Subsequently, a BZY|BZCYYb cell was fabricated and tested using I-V and electrochemical impedance measurements. The results were compared with those of single-layer BZY and BZCYYb cells. The bilayer electrolyte exhibited higher open-circuit voltages, suggesting a reduction in the leakage current. Moreover, the bilayer cell exhibited the lowest ohmic resistance and highest power density. Thus, BZY|BZCYYb bilayer electrolytes can potentially improve the performance and efficiency of PCFCs.

Histological Features of Olfactory Bulb Layers in the African Striped Ground ‎Squirrel (Xerus erythropus)‎

The diurnal African Striped Ground Squirrel (ASGS) (Xerus erythropus), is a member of the rodent order Rodentia and family Sciuridae. Similar to most other vertebrates, the olfactory bulbs (OB) are located most rostrally in the brain and are an integral component of the brain circuitry system responsible for the sense of smell. In this work, the layers and anatomical characteristics of OB in the ASGS were examined. Six (6) adult ASGS were sourced from villages within Zaria Local Government. They were housed in standard laboratory cages and fed with corn and carrot. Water was given ad libitum. The squirrels were euthanized via the abdomen with an injection of ketamine HCL (80mg/kg BW), followed by transcardial perfusion with10% buffered formalin. Craniotomy was carried out to expose the entire brain and the OB was carefully harvested for histological evaluation. Six layers were visible in the olfactory bulb cortex, working their way inward from the outside in. The cells observed were mitral cells, peri-glomerular, granular, and tufted cells. Interestingly, the glomerular layer was observed to be a single layer cell type which is indicative of a good olfactory acuity. It was concluded that African Striped ground squirrel’s one-layered cell thick glomerular layer is indicative of good olfaction and sense of smell giving the ASGS an advantage for navigation in search for food and protection from predation.

Quantitative Operando 7Li NMR Investigations of Silicon Anode Evolution during Fast Charging and Extended Cycling.

The development and optimization of fast battery charging protocols require detailed information regarding lithium speciation inside a battery. Nuclear magnetic resonance (NMR) spectroscopy has the unique capability of identifying the Li phases formed in an anode during Li-ion cell operation and quantifying their relative amounts. In addition, both Li metal films and dendrites are readily detected and quantified. Here, our recently reported parallel-plate resonator radio frequency (RF) probe and the cartridge-type single-layer full cell were used to track the behavior of Si electrodes during cycling and during fast charging. The LixSi compounds formed during electrochemical cycling exhibit an unexpected intrinsic nonequilibrium behavior at both slow and fast rates, evolving toward increasingly disordered local environments. The evolution with time of lithiated phases is nonlinear during both charging and discharging at constant current, unlike the case for pure graphite, and asymmetric between charge and discharge. During charging at rates of 1C, 2C, and 3C, metallic Li in both films and (to a lesser extent) dendritic forms are deposited on the Si anode. Part of the Li metal film formation is reversible, but a fraction remains on the electrode surface as dead Li, while all of the dendritic Li, even though formed in a considerably smaller amount, is entirely irreversible. Such performance-governing properties are critical to the development of fast-charging protocols for lithium-ion batteries (LIBs) and are exceptionally well evaluated and quantified by 7Li magnetic resonance strategies such as those presented here.

Real-Time, Non-Invasive Magnetic Field Imaging for Diagnosing Current Flow Patterns inside Fault-Simulated Li-Ion Batteries

With the growing popularity of Li-ion batteries in electric-powered mobility, securing battery safety has become a common goal of the battery community. Battery failures are commonly caused by small, undetectable defects that can form during manufacturing and operation, ranging from materials to the cell level. Although the small errors inside the cells trigger catastrophic failures, tracing them and distinguishing cell failure modes without cell anatomy remains challenging. Given that several defects within the cell could cause abnormal current flow compared to the normal cells, visualization of the current inside the battery is informative to find and trace the invisible defects that cannot be detected using imaging tools for the internal structure of fully packaged commercial cells.This study presents a real-time, non-invasive magnetic field imaging (MFI) method that can signal the magnetic field induced by battery current flow inside the Li-ion pouch cell during cycling (Figure 1). MFI can offer high-speed scanning in a few minutes (~100 mm/min) and spatially high resolution (0.161 mm2) and immediately measure the magnetic field with no need for shielding commonly required for MRI measurement. Based on the Biot-Savart law, we validated magnetic field-current correlation through the MFI of current-carrying 1D straight wires and 2D planes. Then, we found the optimal pouch cell structure for visualizing the current flow patterns using MFI and successfully converted the MFI contour map of the pouch cells into the normalized current distribution. To demonstrate the efficacy of current pattern analysis, we have collected MFI results of fault-simulated batteries (FSBs) to distinguish failure modes that intentionally possess cell manufacturing faults, such as lead-tab contact failure, electrode alignment, and stacking faults. Magnetic field offset using countercurrent-carrying, pouch cell-shaped 2D conductor underneath can selectively detect the failure spots where the current abnormally flows. It is believed that direct visualization of current distribution patterns and figuring out the pattern changes during operation can expedite the non-destructive, immediate diagnosis of commercial cells and troubleshoot safety-related challenges. Figure 1. Single-layer pouch cells and in operando MFI analysis during charging. (a) Scheme for internal structure of single-layer pouch cell (60 × 90 mm2) with counter-side, center-aligned tabs (CS-C cell). (b) Actual image of CS-C cell and MFI scan and applied current directions during the cell charging. MFI mapping images for (c) Bx , (d) By and (e) Bz vector fields at the cell. White arrows within each MFI contour map indicate the current flow prediction. Applying current density: 5.09 mA cm−2, the cell was situated 6 mm below the sensor (z-distance: 2.5 mm, scanned side: Cathode-side up). The total number of scanned data points are 1699 (11 cm) and 64 (16 cm) in y- and x-directions, respectively. Figure 1

Dry Battery Electrode Manufacturing Enabled By Continuous Powder Mixing

Lithium-Ion Battery electrode manufacturing is a cost- and energy-intensive process that usually relies on the use of a hazardous and expensive solvent, N-methyl-2-pyrrolidone (NMP), for cathodes. After coating the battery-slurry to a current collector, the solvent needs to be evaporated to obtain a porous electrode suitable for the use in a Lithium-Ion Battery. The solvent is a processing material and unwanted in the final product. In fact, solvent residues can fuel parasitic side-reactions within the battery cell and hence deteriorate battery lifetime and safety. The utilization of NMP in battery production plants demands costly labor protection and explosion safety measurements during mixing and coating and necessitates a highly energy and floor-space demanding drying step using thermic drying ovens of up to 100 meters.[1] For ecological and economic reasons, NMP is not emitted in large-scale production facilities, but condensed and recycled by distillation. The NMP-recovery system adds additional floor space and energy demand to the production site. The drying and solvent recovery can account for up to 39% of the total energy demand of a Lithium-Ion Battery Cell production and therefore produce significant CO2 emissions.[2] A solvent-free, dry electrode manufacturing that eliminates the use of solvents hence reduces the floor space, energy demand and cost of a production plant and eases safety and environmental concerns. Different approaches have been reported in the literature to put dry coating into practice,[3],[4] yet most strategies, for example spray coating or brush coating, lack of a feasible implementation into large scale production. In contrast, a dry coating approach that is sometimes referred to as the Maxwell-Process is, according to media reports, currently installed at Tesla’s Gigafactories in Berlin and Austin.[5] In fact, a publicly available teardown of a Tesla 4680 battery cell hints that a dry coated anode could already be used in commercial vehicles.[6] Compared to the state-of-the-art electrode manufacturing process, dry coating requires different polymeric binder systems that form spiderweb-like structures of fine fibrils connecting the electrochemical active particles and the conductive additive particles. PTFE is highly suitable since it is stable towards typical electrolytes and cathode materials and is known to easily form fibrils. These properties are also utilized to produce expanded PTFE membranes like Gore-Tex. The fibril-network in the battery context is primarily formed by a high-shear dry mixing process. The powder mixture is then compressed to a free-standing electrode film (powder-to-film) by a heated rolling mill (calender) and the resulting film is ultimately laminated to a current collector foil (film-to-foil). We demonstrate that a twin screw-extruder can be used to tune the degree of binder-fibrillation during dry-mixing of NMC-based cathode mixtures. Extrusion based mixing allows to use powder mixtures with little amounts of PTFE binder (1 wt%) to produce self-supporting, free-standing cathode films and, ultimately, battery electrodes with high flexibility and sufficient mechanical stability. We show a superior rate-performance and cycling-stability of single-layer pouch cells with dry-coated cathodes compared to cells with wet coated reference electrodes of likewise composition and electrode design. Possible causes for the improved performance focusing on microstructural electrode properties are discussed.[1] Westphal, Bastian G.; Kwade, Arno (2018): Critical electrode properties and drying conditions causing component segregation in graphitic anodes for lithium-ion batteries. In: Journal of Energy Storage 18, S. 509–517.[2] Erik Emilsson, Lisbeth Dahllöf (2019): Lithium-Ion Vehicle Battery Production. IVL Swedish Environmental Research Institute.[3] Duffner, Fabian; Kronemeyer, Niklas; Tübke, Jens; Leker, Jens; Winter, Martin; Schmuch, Richard (2021): Post-lithium-ion battery cell production and its compatibility with lithium-ion cell production infrastructure. In: Nat Energy 6 (2), S. 123–134.[4] Verdier, Nina; Foran, Gabrielle; Lepage, David; Prébé, Arnaud; Aymé-Perrot, David; Dollé, Mickaël (2021): Challenges in Solvent-Free Methods for Manufacturing Electrodes and Electrolytes for Lithium-Based Batteries. In: Polymers 13 (3).[5] https://www.tagesspiegel.de/berlin/tesla-coup-mit-giga-berlin-neue-technologie-soll-wasserverbrauch-minimieren/27244032.html[6] https://www.youtube.com/watch?v=8WPPBhqeekw Figure 1

Understanding the Effects of Uniform Stack Pressure in Extreme Fast Charging Lithium-Ion Batteries Via Operando X-Ray Diffraction

Enabling fast charging in lithium-ion batteries (LIBs) is critical for electric vehicle development, the U.S. goal being to charge to 80% of full capacity in 15 minutes [1]. This is a challenge due to significant capacity fade occurring at charge rates of 6C (charge in 60/6 = 10 minutes) and above. Fast charge rates induce irreversible lithium (Li) plating that adversely impacts battery performance and safety. External stack pressure can improve electrical contact and minimize delamination; further, an understanding of the impact of pressure on capacity fade can provide insight into the degradation mechanisms [2,3]. In this work, we investigate the extreme fast charging (XFC) regime, focusing on cell degradation and parasitic Li plating using single-layer pouch cells with graphite anodes, LiNi0.5Mn0.3Co0.2O2 (NMC532) cathodes, and 1.2 M LiPF6 in 3:7 weight % ethylene carbonate and diethyl carbonate (Gen2 electrolyte). To study the effect of pressure, electrode thickness and material capacity were varied. Cells were cycled under set uniform stack pressure configurations at 6C up to 140 times and tested between 10 – 150 psi. We have characterized fast charging cells under uniform pressure with spatially resolved operando X-ray diffraction (XRD) from high energy, high flux synchrotron radiation to study Li plating, parasitic reactions, and Li intercalation into graphite. Through spatially resolved operando XRD, we have mapped the intensity of LixC6 and Li metal peaks across the electrode to correlate peak intensity as a function of pressure and electrode thickness. This was complemented with ex situ X-ray photoelectron spectroscopy to study the composition of parasitic reaction products, corrosion and to correlate heterogeneity and local Li plating. Our results show an improvement in battery performance with increased uniform pressure. A reduction in Li plating was observed at elevated uniform pressures and Li plating appears more prevalent on the thicker electrodes. We believe that at increased pressure the reduced capacity fade arises from improved wettability, where the electrolyte acts as a lubricant increasing active sights, and a reduction in polarization across the thickness of the electrode leading to more homogenous reaction conditions. We emphasize the importance of electrode stack pressure in XFC batteries by quantifying the degradation mechanisms that cause capacity fade to enable better battery engineering.References USABC Goals – Lithium Electrode Based Cell and Manufacturing for Automotive Traction Applications, USABC (United States Advanced Battery Consortium), http://www.uscar.org/guest/article_view.php?articles_id=85C. Cao et al. J. Electrochem. Soc. 129, 040540 (2022).J. Cannarella and C. B. Arnold, J. Power Source, 245, 745-751 (2014).

Rational designs to enable 10-min fast charging and long cycle life in lithium-ion batteries

A daunting challenge in the design of lithium ion batteries (LiBs) is enabling 10-min extreme fast charging (XFC) while achieving appreciable charge acceptance and cycle life. This desirable outcome requires both a comprehensive understanding of LiB operation and aging behavior at different length scales and careful optimization. Lithium plating has been a critical bottleneck because, at XFC rates, it consumes cyclable lithium causing distinct aging and safety concerns even in moderate-loading LiBs. We propose combining multiple solutions, including materials-to-electrode design-to-charging protocols, that are intended to overcome limitations in lithium-ion transport in the electrolyte phase, thus enabling 10-min XFC in LiBs. Some implemented strategies include cathode chemistry, optimized carbon binder domain in the cathode, dual layer anode design, improved separator and advanced electrolyte. Further, innovative charging protocols in moderately loading (∼ 3 mAh/cm2 anode/2.7 mAh/cm2 cathode) single-layer pouch cells are proposed, together with demonstrated 10-min XFC with higher charge acceptance between 87.3 and 92.1% (or 2–2.1 mAh/cm2) for 600 cycles without lithium plating. This methodical study with well-defined cells shows promise in combining multiple solution strategies to enable 10-min XFC, charting a pathway to achieve XFC in higher-loading energy-optimized LiBs.