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Hard carbon (HC) is recognized as a promising anode material with outstanding electrochemical performance for alkali metal‐ion batteries including lithium‐ion batteries (LIBs), as well as their analogs sodium‐ion batteries (SIBs) and potassium‐ion batteries (PIBs). Herein, a comprehensive review of the recent research is presented to interpret the challenges and opportunities for the applications of HC anodes. The ion storage mechanisms, materials design, and electrolyte optimizations for alkali metal‐ion batteries are illustrated in‐depth. HC is particularly promising as an anode material for SIBs. The solid‐electrolyte interphase, initial Coulombic efficiency, safety concerns, and all‐climate performances, which are vital for practical applications, are comprehensively discussed. Furthermore, commercial prototypes of SIBs based on HC anodes are extensively elaborated. The remaining challenges and research perspectives are provided, aiming to shed light on future research and early commercialization of HC‐based SIBs. [ABSTRACT FROM AUTHOR]

High Li-content lithium garnet oxides are promising solid electrolyte materials for lithium batteries. Being the highest Li-content lithium garnet oxides, Li 7 La 3 Zr 2 O 12 has been reported to crystallize in either the tetragonal or cubic phase with no consensus on the exact conditions under which these two phases are formed, which may be due to unintentional Al contamination and air exposure. In this work, the effects of Ta substitution and H 2 O/CO 2 exposure have been studied under Al-contamination free conditions with minimal air exposure. We showed that 1) the Ta-substitution induced phase transition occurred through a two-phase mechanism and a minimum 0.6 mol of Ta substitution to Zr is needed to stabilize the cubic phase; 2) H 2 O and CO 2 can individually induce the tetragonal-cubic phase transition in Li 7 La 3 Zr 2 O 12 through proton exchange and Li extraction, respectively, which can have great influence on the transport properties of Li 7 La 3 Zr 2 O 12 . [ABSTRACT FROM AUTHOR]

In this paper, macro homogenized material models are adopted to simulate an in-plane constrained punch indentation test of a small-scale lithium-ion battery module specimen. The macro material models are based on the compressive stress–strain curves obtained from representative volume element (RVE) module specimens under in-plane constrained compression tests. The ABAQUS implicit solver is used for simulation of the punch test. The hyperfoam and the crushable foam material models in ABAQUS are adopted to fit the nominal stress–strain curves of the module RVE specimens under in-plane constrained compression. The load–displacement responses and the deformation patterns of the module specimen from the finite element analyses of the punch test based on the hyperfoam and crushable foam material models compare fairly well with the experimental results. However, the initial yielding and the corresponding unloading of the load–displacement curves of the module specimen due to micro buckling could not be modeled distinctively by the macro homogenized models. The computational results show that the material models available in commercial finite element software can be used to reasonably model lithium-ion battery modules under non-uniform compression loading conditions. [ABSTRACT FROM AUTHOR]

Abstract: Mechanical behavior of lithium-ion battery modules is investigated by conducting tensile tests of the module components, constrained compression tests of dry module representative volume element (RVE) specimens, and a constrained punch test of a small-scale dry module specimen. The results of tensile tests of the module components are used to characterize the tensile behavior of module specimens. The results in-plane constrained compression tests of module RVE specimens indicate that the load carrying capacity is characterized by the buckling of the module components and the final densification of the module components, and the nominal stress-strain curves appear to be independent of the specimen height. The results of different compressive nominal stress-strain curves in the in-plane and out-of-plane directions indicate the module RVE specimens are anisotropic. The results of a buckling analysis of the module RVE specimens under in-plane constrained compression are in agreement with the experimental results. The module RVE specimen is dominated by the buckling of the aluminum heat dissipater sheet under in-plane constrained compression. Finally, the results of a constrained punch test of a module specimen are in agreement with those of the corresponding finite element analyses based on a macroscopic homogenized foam material model. [Copyright &y& Elsevier]

Abstract: The mechanical behaviors of lithium iron phosphate battery cells are investigated by conducting in-plane and out-of-plane compression tests of representative volume element (RVE) specimens of dry cells. The test results of cell RVE specimens under in-plane constrained compression indicate that the load carrying behavior of the cell RVE specimens is characterized by the buckling, the kink and shear band formation, and the final densification of the cell components. The SEM images of the active materials on electrodes and the test results of the cell RVE specimens under out-of-plane compression suggest that the porosity in the components and the macroscopic gaps between the components is up to 40%. The test results suggest that the lithium-ion battery cells can be modeled as anisotropic foams or cellular materials. The elastic buckling analyses for a beam with lateral constraints indicate that the higher order buckling modes and the critical buckling stresses in general agree with those observed in experiments. The elastic buckling analyses also justify the length selection of the cell RVE specimens. Finally, an idealized kinematic model is presented to explain the physical mechanisms of the kink and shear band formation in the cell RVE specimens under in-plane constrained compression. [Copyright &y& Elsevier]

Abstract: In this paper, computational models are developed for simulations of representative volume element (RVE) specimens of lithium-ion battery cells under in-plane constrained compression tests. For cell components in the finite element analyses, the effective compressive moduli are obtained from in-plane constrained compressive tests, the Poisson's ratios are based on the rule of mixture, and the stress–plastic strain curves are obtained from the tensile tests and the rule of mixture. The Gurson's material model is adopted to account for the effect of porosity in separator and electrode sheets. The computational results show that the computational models can be used to examine the micro buckling of the component sheets, the macro buckling of the cell RVE specimens, and the formation of the kinks and shear bands observed in experiments, and to simulate the load–displacement curves of the cell RVE specimens. The initial micro buckling mode of the cover sheets in general agrees with that of an approximate elastic buckling solution. Based on the computational models, the effects of the friction on the deformation pattern and void compaction are identified. Finally, the effects of the initial clearance and biaxial compression on the deformation patterns of the cell RVE specimens are demonstrated. [Copyright &y& Elsevier]

Abstract: The most established mathematical description of porous battery electrodes is Newman''s model, which accounts for the behavior of both solid and liquid phases via concentrated solution theory and porous electrode theory. In the present work, formal volume averaging of reformulated generalized Poisson–Nernst–Planck (PNP) equations in the form of concentration and electrochemical potential, or in the form of equivalent circuit on a representative porous microstructure, lead to “upscaled” equations similar to those in Newman''s model. The similarities and differences of the results from the two approaches are discussed throughout the paper. [Copyright &y& Elsevier]

At present, fabrication of all-solid-state lithium-ion batteries using garnet-type electrolytes is still challenging due to issues with interfacial stability and interfacial impedance caused by the high-temperature sintering process. In this work, we employ Li 2 CO 3 as additive to mitigate high-temperature side reactions and prepare an all-solid-state battery LNM|LLZT|LTO using spinel-structured LiNi 0.5 Mn 1.5 O 4 (LNM) and Li 4 Ti 5 O 12 (LTO) as electrodes and garnet-type Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZT) as the electrolyte. The battery voltage reaches beyond 3 V and can be charged and discharged for 5 cycles at a rate of C/10. The three-electrode setup of the battery allows the separation of positive and negative electrodes in their voltage profiles and impedance responses during cycling. Our results suggest that the high-voltage electrode LNM can work with LLZT in a solid-state-battery configuration and the negative electrode is the performance-limiting component. • Li 2 CO 3 is used to mitigate high-temperature side reactions in LNM.|LLZT|LTO. • The voltage of such an all-solid-state battery reaches beyond 3 V. • Three-electrode configuration separates the contributions of electrodes and electrolyte. [ABSTRACT FROM AUTHOR]

Abstract: Lithium-stuffed garnet oxides are promising candidates of lithium ion electrolyte materials due to their high ionic conductivities and good chemical stability. In this study, time-of-flight (TOF) neutron diffraction experiments and the Rietveld refinement were performed on four garnet compounds in the Li7-xLa3Zr2-xTaxO12 (x=0–2) series to study their average structures. Different structural models (split-site and anisotropic displacement) for lithium disorder at tetrahedral (Td) and octahedral (Oh) sites were compared and results suggested possible lithium disorder around both ideal Oh and ideal Td sites. To study the local lithium distribution, atomistic simulations based on static energy minimization with interatomic potentials were carried out on a large number of configurations of eight compositions. We demonstrated that energy probability distribution plots were helpful in understanding the lithium disorder/order in these materials. Nuclear density maps provided a visual presentation of structural disorder at both Td and Oh lithium sites. Our simulation results suggested that Td lithium occupancy is generally lower than that obtained from the average structure (Rietveld refinement) and the exclusion principle (no nearest-neighbor Td–Oh–Td lithium triplets). In addition, the nearest-neighbor Td–Oh lithium pairs and (Oh,□)–Td–(Oh,□) lithium clusters appear to be the characteristic local features contributing to the structure and conduction of these lithium-stuffed garnet oxides. [Copyright &y& Elsevier]

Abstract: The electrolytic deposition of TiO2 thin films on platinum for lithium batteries is carried out in TiCl4 alcoholic solution and the films are subsequently annealed. The as-prepared films are amorphous TiO(OH)2·H2O, transformed into anatase TiO2 at 350°C, and then gradually into rutile TiO2 at 500°C. Cyclic voltammograms show oxidation and reduction peaks at 2.20 and 1.61V, respectively, corresponding to charge and discharge plateaus at 1.98 and 1.75V vs. Li+/Li. The specific capacity decreases with increasing current density for film of 128-nm thickness in the initial discharge. It is observed that the diffusion flux of Li+ insertion/extraction into/from TiO2 controls the reaction rate at higher current densities. Consequently, at low film thickness, high discharge capacity (per weight) is found for the initial cycle at a current density of 10μAcm−2. However, the capacity of prepared films in various thicknesses approach 103±5mAhg−1 after 50cycles, since the formation of cracks for thicker films offers shorter diffusion paths for Li+. In addition, TiO2 films show electrochromic properties during lithiation and delithiation. [Copyright &y& Elsevier]

Composites of few-layer transition metal oxides and graphene nanosheets with strong interfacial connection hold great promise as high-performance anodes for lithium-ion batteries, but it is highly challenging to realize full interfacial properties. Herein, we report an ultra-refined layer-by-layer mesoporous CoO/reduced graphene oxide (CoO/RGO) architecture synthesized via a facile method. The CoO/RGO has stacked interfaces between the CoO nanosheets and the graphene nanosheets via Co–O–C bonds, which has been proposed to have an important role in achieving excellent performance in lithium ion batteries with high initial capacity and good rate capability. It is shown that the CoO/RGO exhibits a high initial discharge capacity of 2189.4 mAh g−1 at a current density of 100 mA g−1. Furthermore, the CoO/RGO exhibits a high reversible capacity retention of 70% after prolonged 300 cycles at a high rate of 2 A g−1. Significantly, it delivers an ultrahigh reversible capacity of 1167 mAh g−1 at 5 A g−1 with an excellent reversible capacity retention of 76% over 40 cycles. • Layered transition metal oxide and graphene nanosheets composite with interfacial Co–O–C bonding has been developed. • CoO/RGO electrode exhibits a discharge capacity of 2189.4 mAh g−1 at 100 mA g−1 and stablizes 300 cycles at 2 A g−1. • CoO/RGO delivers a reversible rate capability of 1167 mAh g−1 at 5 A g−1 with capacity retention of 76%. [ABSTRACT FROM AUTHOR]