High C-rate Research Articles

Design of Na3MnZr(PO4)3/Carbon Nanofiber Free-Standing Cathodes for Sodium-Ion Batteries with Enhanced Electrochemical Performances through Different Electrospinning Approaches.

The NASICON-structured Na3MnZr(PO4)3 compound is a promising high-voltage cathode material for sodium-ion batteries (SIBs). In this study, an easy and scalable electrospinning approach was used to synthesize self-standing cathodes based on Na3MnZr(PO4)3 loaded into carbon nanofibers (CNFs). Different strategies were applied to load the active material. All the employed characterization techniques (X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), thermal gravimetric analysis (TGA), and Raman spectroscopy) confirmed the successful loading. Compared to an appositely prepared tape-cast electrode, Na3MnZr(PO4)3/CNF self-standing cathodes demonstrated an enhanced specific capacity, especially at high C-rates, thanks to the porous conducive carbon nanofiber matrix. Among the strategies applied to load Na3MnZr(PO4)3 into the CNFs, the electrospinning (vertical setting) of the polymeric solution containing pre-synthesized Na3MnZr(PO4)3 powders resulted effective in obtaining the quantitative loading of the active material and a homogeneous distribution through the sheet thickness. Notably, Na3MnZr(PO4)3 aggregates connected to the CNFs, covered their surface, and were also embedded, as demonstrated by TEM and EDS. Compared to the self-standing cathodes prepared with the horizontal setting or dip-drop coating methods, the vertical binder-free electrode exhibited the highest capacity values of 78.2, 55.7, 38.8, 22.2, 16.2, 12.8, 10.3, 9.0, and 8.5 mAh/g at C-rates of 0.05C, 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, 10C, and 20C, respectively, with complete capacity retention at the end of the measurements. It also exhibited a good cycling life, compared to its tape-cast counterpart: it displayed higher capacity retention at 0.2C and 1C, and, after cycling 1000 cycles at 1C, it could be further cycled at 5C, 10C, and 20C.

Quasi-diffusion controlled high rate sodium-ion storage performance of flame pyrolysis derived spherical hard carbon

Hard carbon (HC) is identified as a potential anode for sodium ion batteries (SIBs) due to its outstanding electrochemical performance. However, selection of synthesis routes and its precursors remain crucial to develop the HC of desired microstructures for enhanced sodium-ion storage. Herein, we employed novel flame pyrolysis route to prepare spherical HC nanoparticles (<100 nm) from a liquid precursor derived from a low-cost bio-source. The as prepared carbon has been subjected to different calcination temperatures to optimize the porosity and surface area in order to achieve maximum sodium ion storage. The HC calcined at 1200 °C has shown the optimum electrochemical performance with a high reversible capacity of ∼287 mAh/g at 0.1C (1C = 300 mA/g). It shows 72 % of capacity retention after 490 cycles when cycled at 1C, with initial reversible specific capacity of ∼235 mAh/g. Excellent rate performance has been seen even at 20 C (6 A/g) with high specific capacity of 118 mAh/g at 70 % capacity retention after 2000 cycles, which is one of the highest values reported so far. Structural and morphological characterization of HC prepared at different temperatures are carried out using X-ray powder diffraction (XRD), small angle X-ray scattering (SAXS), Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. Particle size and morphology altogether have played significant role in achieving high specific capacity and C-rate performance by providing shorter diffusion path and larger sodium ion storage sites.

Silicon-tin thin-film anodes for low and high power-density lithium-ion batteries

Silicon (Si) is a promising replacement material for graphite, the commonly utilized anode material in lithium-ion batteries (LIBs). Si has a theoretical specific capacity up to 11 times higher than that of graphite. However, pure Si has two main issues: high electronic resistivity and significant volume change during charge/discharge cycling. To overcome these issues, Si was alloyed with high-conductivity materials. In this contribution, physical vapor deposition was utilized to produce binderless silicon-tin anodes for LIBs. Tin is a lithium-active alloying material that has high electrical conductivity and high specific capacity (i.e., up to three times that of graphite). Electronic resistivity, residual film stress, X-ray photoelectron spectroscopy, Raman spectroscopy, and cyclic voltammetry measurements were performed to thoroughly analyze the deposited Si-Sn films and help understand their charge/discharge cycling performance at low and high C-rates. At a low C-rate of 0.5 C, the alloyed films did not show any improvement compared to pure Si. However, the alloyed films showed better performance compared to pure Si when tested at a high C-rate of 10 C. Si-Sn films with (40 – 50 wt.% Sn) were able to retain a specific capacity of around 680 mAh g−1 after 1000 cycles.

Facile Synthesis and Electrochemical Analysis of Zn-Doped V2O5 Anode Materials for High-Rate Li Storage

The surging demand for Li rechargeable batteries with high energy densities and rapid rate capability has propelled research on materials that can replace the conventional anode materials like graphite. Vanadium pentoxides (V2O5) have emerged as promising anode candidates owing to their excellent rate capability. Specifically, V2O5 allows the electrochemical prelithiation process, in which three Li-ions can be inserted to form Li3V2O5, followed by reversible insertion and extraction of two Li-ions. Nevertheless, the unsatisfactory Li-ion diffusion coefficients and electrical conductivities of these materials remain major drawbacks. Here, we propose a Zn-doped V2O5 anode, fabricated using a two-step sol–gel method, for high-rate Li-ion batteries. Zn was incorporated into V2O5 to enhance the Li-ion transport kinetics through the electrode. The crystal structure (orthorhombic) of Zn-doped V2O5 was identified by X-ray diffraction analysis, and the Zn doping was confirmed by X-ray photoelectron microscopy. The effect of Zn doping was thoroughly examined using various analytical methods, such as cyclic voltammetry and galvanostatic intermittent titration technique. The Zn-doped V2O5 electrode exhibited remarkable cycling durability, enduring for 1000 cycles, while retaining an enhanced capacity, even under a high rate of 2C.

Effects of W-doping on precursor growth of LiNi0.88Co0.09Mn0.03O2 and its electrochemical performance

W-doped LiNi0.88Co0.09Mn0.03O2 cathodes were fabricated by using W-doped precursors. X-ray diffraction indicates that W-doping suppresses the crystal growth of the precursor along the direction perpendicular to c-axis. Scanning electron microscopy results show that the primary particles of the cathode become finer with the increase of W-doping amount. Electrochemical measurements prove the merits of the W-doped cathodes. The one with 0.4 wt.% W-doping shows significantly improved electrochemical properties compared with the pristine one. After 100 charge–discharge cycles at a high rate of 10C, it exhibits capacity retentions of 94.68% and 89.63% at 25 and 45 °C, respectively. The intergranular cracks after cycles are also suppressed by W-doping. Hence, profiting from the synergistic effect of component regulation and microstructure engineering by W-doping, the Li+ diffusion kinetics is boosted, and the structural stability is enhanced.

Enabling High-Performance Battery Electrodes by Surface-Structuring of Current Collectors and Crack Formation in Electrodes: A Proof-of-Concept

Today's society and economy demand high-performance energy storage systems with large battery capacities and super-fast charging. However, a common problematic consequence is the delamination of the mass loading (including, active materials, binder and conductive carbon) from the current collector at high C-rates and also after certain cycle tests. In this work, surface structuring of aluminum (Al) foils (as a current collector) is developed to overcome the aforementioned delamination process for sulfur (S)/carbon composite cathodes of Li-S batteries (LSBs). The structuring process allows a mechanical interlocking of the loaded mass with the structured current collector, thus increasing its electrode adhesion and its general stability. Through directed crack formation within the mass loading, this also allows an enhanced electrolyte wetting in deeper layers, which in turn improves ion transport at increased areal loadings. Moreover, the interfacial resistance of this composite is reduced leading to an improved battery performance. In addition, surface structuring improves the wettability of water-based pastes, eliminating the need for additional primer coatings and simplifying the electrode fabrication process. Compared to the cells made with untreated current collectors, the cells made with structured current collectors significantly improved rate capability and cycling stability with a capacity of over 1000mAhg−1. At the same time, the concept of mechanical interlocking offers the potential of transfer to other battery and supercapacitor electrodes.

Evaluating 3D printed mesh geometries in ceramic LiB electrodes

Additive manufacturing techniques have the potential to promote a paradigmatic change in the electrode fabrication processes for lithium-ion batteries (LiBs) as they may offer alternative component designs to boost their performance or to customise the application. The present research work explores the use of low-cost fused filament fabrication (FFF) 3D printing to fabricate Li4Ti5O12 (LTO) mesh electrodes in the search for enlarged electrochemically active areas. Using different nozzle diameters (ND), we have 3D printed several mesh electrodes that after sintering allow an increase in the surface to volume ratio by up to ≈290% compared to conventional flat cylindrical geometries. As the conventional route to produce 3D printed meshes, i.e. stacking of consecutive layers with a 90° rotation, leads to problems of vertical misalignment that may affect the electrical contact, we have developed a new compact design that maximises the contact between layers. All the 3D printed mesh electrodes with thicknesses of 400 and 800 μm, exhibit electrochemical performance very close to those of thin (70 μm) electrodes, e.g. 175 mAh g−1 at C/2 in the case of ND = 100 μm, which is the theoretical capacity value for LTO. At higher C-rates, 800 μm-thick mesh electrodes with larger ND exhibit a marked drop in the reversible capacity (28 mAh g−1 at 8 C), although the values obtained improve notably those of the equivalent thick solid electrode (almost null at 8 C). The compact design demonstrated superior performance at high C-rates, improving by ≈70% the results of the best conventional mesh electrode at 8 C for 800 μm electrodes. These results highlight the potential of FFF-3D printing to generate novel high aspect ratio geometries and the impact of design and printing parameters on the performance of LiB electrode materials. Exploring alternative efficient geometries may facilitate the integration of thick electrodes in high energy density LiBs.

Constructing Li2C4O4 and conductive carbon synergistic Double-Layer modified separator for Kinetics-Enhanced Li–S batteries

Lithium-sulfur (Li-S) batteries have been considered as satisfying energy storage devices, but the electrochemical performance of Li-S batteries is severely hindered by the shuttle effect and the sluggish sulfur redox kinetics. Herein, a double-layer separator modified with Li2C4O4 and Super P through a simple coating method is prepared. The composite Li2C4O4-Super P exhibits great adsorption on polysulfides. Besides, the combination of Li2C4O4 and Super P can reduce charge transfer resistance and improve Li+ transport ability. The Li2C4O4-Super P@PP cell shows an extremely low capacity decay rate of 0.045 % after 800 cycles at 1C and a fantastic capacity of 588.1 mAh·g−1 under the high rate of 5C.

Investigating the Path Dependent Aging Behavior of Nickel Cobalt Aluminum Oxide Cathode Batteries During High C-rate Cycling Conditions

Nickel-rich cathode material batteries such as the nickel cobalt aluminum oxide with graphite anode are common in the automotive sector due to their high energy density and power performance capabilities, however, they are limited in lifetime performance. Accelerated degradation in specific operation conditions, such as high C-rates are known to significantly contribute to this issue. To better understand a chronological dependence of these high-stress conditions occurring during battery lifetime, a path dependent aging study is performed using profiles inspired by high-performance race operation. The focus on C-rates >1C during charging and discharging using real-world inspired profiles- known to induce particle cracking or lithium plating- addresses the need to understand aging behavior in less studied, but highly relevant high-performance automotive context. The aging conditions were tailored to induce specific degradation modes to better identify potential degradation mode coupling. Using differential voltage and capacity analysis techniques, degradation modes were identified which likely contributed to path dependent aging behavior, including loss of lithium inventory and loss of active material in the positive electrode. Two critical paths were identified in this study where later high C-rate conditions in the form of fast-charging at temperatures of 25 °C resulted in accelerated aging and where loss of lithium inventory induced stresses in the positive electrode, accelerating loss of active material.

Surface-coated AlF3 nanolayers enable polysulfide confinement within biomass-derived nitrogen-doped hierarchical porous carbon microspheres for improved lithium-sulfur batteries

The electrically insulating and volumetric deformation of sulfur and the shuttle effect of the intermediate lithium polysulfide (LiPSs) have severely hindered the development of lithium-sulfur batteries (LSBs). Herein, a synergistic strategy of hierarchical porous nitrogen-doped carbon microspheres (PNCM) derived from low-cost biomass with surface-coated AlF3 nanolayer as a multifunctional sulfur host (denoted as PNCM@S@AlF3) was developed. The PNCM not only possesses an abundant pore structure, large surface area, and high electrical conductivity but also features an intrinsic N-doped and fluorinated framework, which effectively enhances the physical adsorption and chemical anchoring to LiPSs. In addition, the AlF3 nanolayer protects the open surface of the porous carbon to isolate sulfur species from the electrolyte to reduce irreversible losses while accelerating the redox kinetics of LiPSs through strong polar adsorption and bonding. Hence, the PNCM@S@AlF3 cathode exhibits an initial capacity as high as 1176.2 mAh/g at 0.2C, and the cycling stability and rate capability are superior to that of PNCM@S without AlF3 coating. Impressively, the PNCM@S@AlF3 cathode delivers stable long-term cycling performance at a high rate of 2C, with 95.6% capacity retention after 500 cycles. This work presents a facile, sustainable, and efficient synergistic strategy for developing advanced LSBs.

A modified high C-rate battery equivalent circuit model based on current dependence and concentration modification

The current battery equivalent circuit models are mainly suitable for room temperature or low C-rate conditions. However, the polarization phenomenon is serious at high C-rate, which results in the obvious voltage drop and significantly reduces the model accuracy at high C-rate. In this paper, the characteristics analysis of different RC models is firstly studied. It is found that the first-order RC circuit model is more suitable for high C-rate conditions due to the coupling of model parameter extraction. Based on the first-order RC model, a basic equivalent circuit model adapted to high C-rate condition is then determined. Secondly, the influences of sampling frequency and the identified time domain on instantaneous impedance and polarization resistance are researched. Thirdly, the change rules of different polarizations at high C-rate are analyzed. Furthermore, the relationship between the change rule of the model parameters and that of different overpotentials are researched. Subsequently, a modified high C-rate model is innovatively established, which considers the current dependence and concentration/temperature modification of instantaneous impedance and polarization resistance. Finally, the accuracy of the modified high C-rate model is verified at 5 °C, 25 °C, and 55 °C, respectively. Results show that the modified high C-rate model can improve the simulation accuracy of the voltage at high C-rate (≤6C), and the mean absolute error (MAE) and Root Mean Squared Error (RMSE) are within 68 mV. Compared with the existing high C-rate model, the accuracy of the modified high C-rate model proposed in this paper is improved and the complexity is also significantly reduced.

Hit two birds with one stone: A bi-functional selenium-substituted organosulfur polymer additive for high-performance lithium-sulfur batteries

Sluggish reaction kinetics of sulfur cathode and high reactivity of lithium anode hinder the commercialization of Li-S batteries. Employing the electrolyte additive to regulate the states of active material is a facile and effective way to solve the above issues. Herein, the bifunctional selenium substituted lithium polythioctic acid (PTA-Se) was prepared as an additive of electrolyte via in-situ polymerization and substitution method. Such additives can promote the conversion of polysulfides and facilitate the homogenization of Li-ion flux. The active selenium sites provide a kinetically favorable pathway for polysulfide conversion. The introduction of additives also facilitates the formation of elastic and uniform solid electrolyte phase interface (SEI) film on the surface of lithium anode. As results, Li-S batteries assembled with PTA-Se additive demonstrates a high initial capacity of 1319 mAh g−1 at 0.2C with 1000 mAh g−1 remaining after 150 cycles, corresponding to a 0.16 % capacity decay per cycle. At a high rate of 5C, the cell still achieves a reversible capacity of 517 mAh g−1. This work opens a new avenue for designing effective electrolyte additive and achieving high-performance Li-S batteries.

Biobased Acrylic Latexes/Sodium Carboxymethyl Cellulose Aqueous Binders for Lithium-Ion NMC 811 Cathodes.

The increasing demands for sustainable energy storage technologies have prompted extensive research in the development of eco-friendly materials for lithium-ion batteries (LIBs). This research article presents the design of biobased latexes, which are fluorine-free and rely on renewable resources, based on isobornyl methacrylate (IBOMA) and 2-octyl acrylate (2OA) to be used as binders in batteries. Three different compositions of latexes were investigated, varying the ratio of IBOMA and 2OA: (1) Poly2OA homopolymer, (2) Poly(2OA0,6-co-IBOMA0,4) random copolymer, and (3) PolyIBOMA homopolymer. The combination of the two monomers provided a balance between rigidity from the hard monomer (IBOMA) and flexibility from the soft one (2OA). The study evaluated the performance of the biobased latexes using sodium carboxymethyl cellulose (CMC) as a thickener and cobinder by fabricating LiNi0.8Mn0.1Co0.1O2 (NMC 811) cathodes. Also, to compare with the state of the art, organic processed PVDF electrodes were prepared. Among aqueous slurries, rheological analysis showed that the CMC + Poly(2OA0,6-co-IBOMA0,4) binder system resulted in the most stable and well-dispersed slurries. Also, the electrodes prepared with this latex demonstrated enhanced adhesion (210 ± 9 N m-1) and reduced cracks compared to other aqueous compositions. Electrochemical characterization revealed that the aqueous processed cathodes using the CMC + Poly(2OA0,6-co-IBOMA0,4) biobased latex displayed higher specific capacities than the control with no latex at high C-rates (100.3 ± 2.1 vs 64.5 ± 0.8 mAh g-1 at 5C) and increased capacity retention after 90 cycles at 0.5C (84% vs 81% for CMC with no latex). Overall, the findings of this study suggest that biobased latexes, specifically the CMC + Poly(2OA0,6-co-IBOMA0,4) composition, are promising as environmentally friendly binders for NMC 811 cathodes, contributing to the broader goal of achieving sustainable energy storage systems.

A Novel Quick Temperature Prediction Algorithm for Battery Thermal Management Systems Based on a Flat Heat Pipe

Predicting the core temperature of a Li-ion battery is crucial for precise state estimation, but it is difficult to directly measure. Existing quick temperature-predicting approaches can hardly consider the thermal mass of complex structure that may cause time delays, particularly under high C-rate dynamic conditions. In this paper, we developed a quick temperature prediction algorithm based on a thermal convolution method (TCM) to calculate the core temperature of a flat heat pipe-based battery thermal management system (FHP-BTMS) under dynamic conditions. The model could predict the core temperature rapidly through convolution of the thermal response map which contains full physical information. Firstly, in order to obtain a high fidelity spatio-temporal temperature distribution, the thermal capacitance-resistance network (TCRN) of the FHP-BTMS is established and validated by constant and dynamic discharging experiments. Then, the response map of the core temperature motivated by various impulse heat sources and heat sinks is obtained. Specifically, the dynamic thermal characteristics of an FHP are discussed to correct the boundary conditions of the TCM. Afterwards, the temperature prediction performances of the TCM and a lumped model under different step operating conditions are compared. The TCM results show a 70–80% accuracy improvement and better dynamic adaptivity than the lumped model. Lastly, a vertical take-off and landing (VTOL) profile is employed. The temperature prediction accuracy results show that the TCM can maintain a relative error below 5% throughout the entire prediction period.

Y-tube assisted coprecipitation synthesis of iron-based Prussian blue analogues cathode materials for sodium-ion batteries.

Prussian blue analogues possess numerous advantages as cathode materials for sodium-ion batteries, including high energy density, low cost, sustainability, and straightforward synthesis processes, making them highly promising for practical applications. However, during the synthesis, crystal defects such as vacancies and the incorporation of crystal water can lead to issues such as diminished capacity and suboptimal cycling stability. In the current study, a Y-tube assisted coprecipitation method was used to synthesize iron-based Prussian blue analogues, and the optimized feed flow rate during synthesis contributed to the successful preparation of the material with a formula of Na1.56Fe[Fe(CN)6]0.90□0.10·2.42H2O, representing a low-defect cathode material. This approach cleverly utilizes the Y-tube component to enhance the micro-mixing of materials in the co-precipitation reaction, featuring simplicity, low cost, user-friendly, and the ability to be used in continuous production. Electrochemical performance tests show that the sample retains 69.8% of its capacity after 200 cycles at a current density of 0.5C (1C = 140 mA g-1) and delivers a capacity of 71.9 mA h g-1 at a high rate of 10C. The findings of this research provide important insights for the development of high-performance Prussian blue analogues cathode materials for sodium-ion batteries.

Architecting the Microenvironment Skeleton of Active Materials in High-Capacity Electrodes by Self-Assembled Nano-Building Blocks.

In analogy to the cell microenvironment in biology, understanding and controlling the active-material microenvironment (ME@AM) microstructures in battery electrodes is essential to the successes of energy storage devices. However, this is extremely difficult for especially high-capacity active materials(AMs) like sulfur, due to the poor controlling on the electrode microstructures. To conquer this challenge, here, a semi-dry strategy based on self-assembled nano-building blocks is reported to construct nest-like robust ME@AM skeleton in a solvent-and-stress-less way. To do that, poly(vinylidene difluoride) nanoparticle binder is coated onto carbon-nanofibers (NB@CNF) via the nanostorm technology developed in the lab, to form self-assembled nano-building blocks in the dry slurry. After compressed into an electrode prototype, the self-assembled dry-slurry is then bonded by in-situ nanobinder solvation. With this strategy, mechanically strong thick sulfur electrodes are successfully fabricated without cracking and exhibit high capacity and good C-rate performance even at a high AM loading (25.0mgcm-2 by 90wt% in the whole electrode). This study may not only bring a promising solution to dry manufacturing of batteries, but also uncover the ME@AM structuring mechanism with nano-binder for guiding the design and control on electrode microstructures.

Mitigating irreversible phase transition of Y-doped LiNi0.925Co0.03Mn0.045O2 by lattice engineering

The commercialization of ternary layered cathode materials with a relative nickel content of more than 90 % faces serious challenges. Among them, it is urgent to address the issues of rapid capacity degradation and structural degradation. Herein, we provide a simple process for doping yttrium at the precursor preparation stage. The feasibility of yttrium doping in the precursor and the positive effects of yttrium ions on the crystal structure and properties of the cathode materials are scientifically explained by a variety of characterization and testing methods, such as Eh-pH, Particle Size Analyzer, ICP, SEM, EDS, XRD, XPS, HRTEM, dQ/dV, CV, EIS and DFT. Yttrium-doped NCMY cathode materials have more stable lattice oxygen and significantly less irreversible phase transition. Furthermore, the electrochemical performance of the NCMY cathode material is significantly improved, with a capacity retention rate of 82.71 % after 150 cycles at a current density of 1C, which is much higher than 65.39 % for NCM. The NCMY cathode material significantly improves the lithium ion diffusion ability, especially at the high rate of 10C, the discharge specific capacity is still as high as 177.05 mAh g−1.

A flexible fiber-shaped solar chargeable zinc–polyaniline battery with a fullerene-based electron transfer layer

Wearable electronic devices demand monolithic solar rechargeable batteries that directly convert photon energy into electricity. Solar rechargeable batteries consist of an active material with electron-hole separation and energy storage ability. In an aqueous zinc-ion battery, a staggered p-n junction comprising n-type fullerene plasma-induced carbon clusters (FPC) and p-type polyaniline (PANI) is employed for a photoelectrode active material. The FPC material acts as an electron transfer layer to block the recombination of photoexcited electrons and holes generated in PANI under illumination. We fabricated an FPC–PANI-based solar battery that exhibited photo-enhanced capabilities of 300 % at a high C-rate, with a high capacity of 310 mAh g−1 and a capacity retention of 91.3 % for 2000 cycles upon light irradiation. After illumination for 10 h, the synergy between the photocathode and photoanode in the fiber-shaped configuration resulted in a record-high photon energy conversion efficiency of 1.15 %, with high-flexibility performances as a wearable device.

(Invited) A "Master Curve" for Plating Onset, Reaction Inhomogeneity during Fast Charging: Experiment and Theory

Inhomogeneous intercalation in porous anodes may lead to accelerated lithium plating during fast charging. This reaction inhomogeneity can occur both at the particle level or at the length scale set by the electrode thickness. Many studies have investigated the effects of various physical and electrochemical properties (e.g., ionic and mass transport, interface reaction kinetics, electrode thermodynamic behavior) on reaction inhomogeneity. However, their effect on accelerated lithium plating at high C-rates has not been fully elucidated. In this work, theory and experiment are used to study how reaction inhomogeneity and plating are related at high C-rates. It is shown that a non-dimensional number, the “reaction inhomogeneity parameter” λ, can be used to predict plating onset in graphite half-cells with a simple analytical solution derived from porous electrode theory, so long as anode particles are sufficiently small. Experiments measuring lithium plating onset in a small-particle graphite at various C-rates and thicknesses can be normalized to a single “master curve” for plating onset when plotted as a function of λ. These comparisons validate the theoretical predictions from both analytical and numerical modeling. Further, experiments with in situ visual inspection of local intercalation in graphite demonstrate that this λ parameter can predict reaction inhomogeneity measured using various metrics. These combined results support the numerical prediction that reaction inhomogeneity on the electrode length scale is responsible for accelerated plating at high charge rates for small-particle graphite. Further, it is shown with theory that this normalization procedure may be applicable for varied porosity, tortuosity, electrolyte materials and different anode materials. Finally, it is demonstrated that use of this “master curve” can be extended to patterned electrodes where channeled architectures are used to improve high C-rate charging.

Insights into the Electrochemical Degradation of Aluminum Dual-Ion Batteries: Influence of Internal Cell Resistance & Applied Current Density

To face the upcoming demand on high-power energy storage systems, e.g, for high-dynamic grid-stabilization , stationary devices as used in photovoltaics, and mobile applications led to invention of various battery technologies like sodium-ion batteries (SIB), zinc-ion batteries (ZIB) and high-power lithium-ion batteries (LIBs). Especially the several lithium-ion battery technologies have in common that currently used raw materials like lithium-salts and heavy metals (Ni, Co, Mn) are becoming increasingly scarce and therefore expensive. Without substitution by less-critical materials the ongoing energy system transformation cannot be successfully achieved.One promising system that gained attention in the last few years is the so-called aluminum graphite dual-ion battery (AGDIB). The active electrodes are made of cheap and abundant materials like graphite as cathode material and an aluminum-foil as anode1. During operation chloroaluminate anions from the electrolyte, which is currently based on ionic liquids like 1-ethyl-3-methylimidazoliumchloride ([EMIm]Cl) and AlCl3 in stoichiometric ratios as well as deep-eutectic solvents based on mixtures of urea and AlCl3, are (de)intercalated in the graphitic host-structure while on the anode metallic aluminum is electrochemically deposited and dissolved see equation (1) and (2), respectively2, 3. The overall mechanism is quite comparable with Li-metal batteries, where metallic Li is reversibly dissolved and deposited.The big advantages of AGDIBs are cheap electrode materials (graphite & aluminum), electrolytes based on urea and an extraordinary high-power cell-chemistry. Recent publications showed charging rates up to 20 A g-1 Graphite equal to 9 kW kg-1 Graphite in laboratory-scaled cells. Also, the lifetime of those batteries seems to be non-competitive, cycles up to half a million were reported with negligible capacity fading or degradation effects.4 To develop scalable and more representative battery cells, we established the AGDIB cell chemistry in a new corrosion-stable pouch bag design. Due to the significant increased electrode surface area and overall capacity, hitherto unknown effects were observed which limited the end of lifetime (EOL) of those batteries to less than 8,000 cycles. Herein, we report on a detailed analysis of the cell failure, including several electrochemical in-situ techniques like galvanostatic intermittent titration techniques (GITT), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV).5 The obtained data will allow a fundamental understanding of the cell operation under low (≤ 1 C-rates) and very high C-rates ≥ 15 C, which is important for establishing a durable AGDIB with high cycling stability.References M.-C. Lin, M. Gong, B. Lu, Y. Wu, D.-Y. Wang, M. Guan, M. Angell, C. Chen, J. Yang, B.-J. Hwang and H. Dai, Nature, 520(7547), 325–328 (2015). M. L. Agiorgousis, Y.-Y. Sun and S. Zhang, ACS Energy Lett., 2(3), 689–693 (2017). M. Angell, G. Zhu, M.‐C. Lin, Y. Rong and H. Dai, Adv. Funct. Mater., 30(4), 1901928 (2020). G. A. Elia, N. A. Kyeremateng, K. Marquardt and R. Hahn, Batteries & Supercaps, 2, 83–90 (2019).M. Safari and C. Delacourt, J. Electrochem. Soc., 158(10), A1123 (2011). Figure 1