All-solid-state Li-ion Batteries Research Articles

High-throughput screening of halide solid-state electrolytes for all-solid-state Li-ion batteries through structural descriptor

All-solid-state Li-ion batteries (ASSLIBs) have attracted great attention due to their intrinsic safety and high potential energy density. To realize ASSLIBs, the development of solid-state electrolytes (SSEs) with favorable electrochemical stability and high Li-ion conductivity is of utmost significance. Compared to trial-and-error searches, theoretical computation-based methods are recognized as a powerful tool for accelerating the exploration of SSEs. However, the development of appropriate descriptors is often the first hurdle toward implementing accurate and meaningful screening process. Here we quantified the structural properties pertaining to low Li-ion migration barriers and performed a high-throughput screening of 3119 Li-containing halides obtained from the Materials Project (MP) database to search for promising SSEs. After excluding previously reported SSEs, three candidate materials, Li4ZrF8, Li3ErBr6, and Li2ZnI4 with crystal structure exhibiting 3D diffusion pathway were obtained. Subsequent theoretical calculations of these materials were performed to evaluate their thermodynamic stability, chemical/electrochemical stability, and ionic conductivity. The three halide materials appeared to be promising SSE candidates due to their robust thermodynamical stability against cathodes, and high ionic conductivity. This research provides a new insight and a systematic quantitative understanding of the relationship between the structural properties and Li-ion migration barriers, which can motivate future computational studies on new fast-ion conductors and accelerate the discovery of high ionic conductivity SSEs for the use in ASSLIBs.

Development of High-Performance Cathodes for Inorganic Halide All-Solid-State Li-Ion Batteries

Electric vehicles (EVs), representing the future of transportation, are predicted to be one of the ultimate solutions to eliminate greenhouse gas emissions. Li-ion batteries (LIBs), as the most promising sustainable energy devices, are critical for the development of EVs because of their higher operating voltages compared to other energy storage technologies. However, the development of conventional LIBs touched the ceiling because of three main challenges. (1) The use of flammable and toxic liquid electrolytes brings high safety risks. (2) The limited energy density of LIBs cannot satisfy the requirement for long-range EVs. (3) The increasing market demand for LIBs will cause resource shortage and rise of cost.[1] Accordingly, all-solid-state Li-ion batteries (ASSLIBs) have recently emerged as promising alternative batteries for next-generation EVs because of their ability to overcome the drawbacks of conventional LIBs. Among the developed solid-state electrolytes (SSEs), inorganic SSEs (e.g., sulfide SSEs, halide SSEs) have high Li+ conductivity at 10-3 S cm-1 and improved interfacial stability, demonstrating stable cycling performance in ASSLIBs.[2] However, inorganic ASSLIBs still face some key challenges hindering their application in EVs. For example, the rate capability of inorganic ASSLIBs still falls far below the requirements of fast-charging EVs (full-charged in 15 min). In addition to the effect of Li+ conductivity in SSEs, Li+/e- transfer kinetics at the cathode interface and in cathode materials are also critically important for the high-rate capability of inorganic ASSLIBs. In this talk, I will first review our previous studies on cathode interface in inorganic ASSLIBs.[3-7] After that, I will introduce our most recent research on unveiling the kinetic limitation of cathode interfaces in inorganic ASSLIBs by synchrotron-based spectromicroscopy. Our research suggests that poor Li+/e- transfer kinetics at the cathode/SSE interface and in the cathode bulk structure are the key limitation for the low capacity of inorganic ASSLIBs under high-rate charge-discharge cycles.

Pressure‐Induced Pre‐Lithiation Enables High‐Performing Si Anodes in All‐Solid‐State Batteries

A commentary on pressure‐induced pre‐lithiation towards Si anodes in all‐solid‐state Li‐ion batteries (ASSLIBs) using sulfide electrolytes (SEs) is presented. First, feasible pre‐lithiation technologies for Si anodes in SE‐based ASSLIBs especially the significant pressure‐induced pre‐lithiation strategies are briefly reviewed. Then, a recent achievement by Meng et al. in this field is elaborated in detail. Finally, the significance of Meng's work is discussed.

Development of Si-Based Anodes for All-Solid-State Li-Ion Batteries

All-solid-state Li-ion batteries (ASSBs) promise higher safety and energy density than conventional liquid electrolyte-based Li-ion batteries (LIBs). Silicon (Si) is considered one of the most promising anode materials due to its high specific capacity (3590 mAh g−1) but suffers from poor cycling performance because of large volumetric effects leading to particle pulverization, unstable solid electrolyte interphase (SEI), and electric disconnection. In ASSBs, additional issues such as poor solid–solid contacts and interfacial side reactions between Si and solid-state electrolytes (SSEs) are also hindering their practical application. This review first outlines the prospects and recent research achievements of Si-based anodes with special focuses on various Si structures and composite materials, then analyzes the issues of electrochemical–mechanical effects, and finally summarizes key factors and promising strategies for further improving Si-based anodes for high-performance ASSBs.

Surface Lattice Modulation Enables Stable Cycling of High-Loading All-solid-state Batteries at High Voltages.

Halide solid electrolytes, known for their high ionic conductivity at room temperature and good oxidative stability, face notable challenges in all-solid-state Li-ion batteries (ASSBs), especially with unstable cathode/solid electrolyte (SE) interface and increasing interfacial resistance during cycling. In this work, we have developed an Al3+-doped, cation-disordered epitaxial nanolayer on the LiCoO2 surface by reacting it with an artificially constructed AlPO4 nanoshell; this lithium-deficient layer featuring a rock-salt-like phase effectively suppresses oxidative decomposition of Li3InCl6 electrolyte and stabilizes the cathode/SE interface at 4.5 V. The ASSBs with the halide electrolyte Li3InCl6 and a high-loading LiCoO2 cathode demonstrated high discharge capacity and long cycling life from 3 to 4.5 V. Our findings emphasize the importance of specialized cathode surface modification in preventing SE degradation and achieving stable cycling of halide-based ASSBs at high voltages.

Effect of Ca doping on Li ion conductivity of Ge and Ta doped garnet LLZO

The series Li6.55+xGe0.05La3-xCaxZr1.75Ta0.25O12 (x = 0, 0.05, 0.10, 0.15, 0.20) was prepared by conventional solid state reaction method with the sintering temperature of 1050 °C for 7.30 h by substituting Ca at the La site to increase the Li ion conductivity. The synergistic effects of Ca incorporation on Li6.55Ge0.05La3Zr1.75Ta0.25O12 were studied using various structural and electrochemical analyses. X-ray diffraction, scanning electron microscopy, and Impedance analysis were used to determine the crystal structure, morphology, and AC conductivity of the prepared ceramic samples, respectively. The highest conductivity of 9.95 x 10−4 S/cm was obtained for a 0.05 Ca ceramic sample with minimum activation energy of 0.23 eV. The DC polarization measurements confirmed the dominance of ionic conduction in 0.05 Ca ceramic. The results obtained make the 0.05 Ca ceramic sample a promising candidate as solid electrolytes for all solid state Li-ion batteries (ASSLIBs).

Highly reliable and large-scale simulations of promising argyrodite solid-state electrolytes using a machine-learned moment tensor potential

The high ionic conductivity of argyrodite makes it an attractive candidate for solid-state electrolytes (SSEs) in all-solid-state Li-ion batteries (ASSBs). Although great effort has been devoted to using ab initio molecular dynamics (AIMD) to evaluate ionic conductivity and elucidate the Li-ion diffusion mechanism of argyrodite-based SSEs, limitations in system size, simulation temperatures, and time associated with AIMD make accurate predictions and analysis of Li-ion diffusion challenging. Here, we present a reliable, large-scale computational approach to realistic simulation of SSEs in the bulk and at the grain boundary (GB) based on moment tensor potentials (MTPs) trained at the van der Waals optB88 level of theory. MTPs enable sufficiently large-scale and long-time simulations that reflect all possible configurational disorder of experimental crystal structures and provide accurate ionic conductivities that are close to values measured experimentally in halogenated Li-argyrodite (Li6PS5X [X = Cl, Br, I]). Our simulations show that the vibrational motion of a PS4 polyhedron has a positive effect on ionic conductivity. We also developed an accurate MTP using an active-learning approach to exploring Li-ion diffusion at the GB in polycrystalline SSEs. Simulations of the molecular dynamics of large ∑5100021 (>10,000-atom) GB models reveal that Li-ion accumulation around the GB region retards ionic conductivity and extends into an interior region approximately 20 Å from the GB interface. This work provides a practical approach to realistic large-scale and interfacial GB simulations that are otherwise inaccessible through ab initio calculations by developing accurate machine-learned MTPs.

Impedance Variation of All-Solid-State Battery Cell Using Li10GeP2S12; States-of-Charge Dependence Visualized by Distribution-of-Relaxation Time Analysis

Electrochemical impedance spectroscopy (EIS) will support understanding of electrochemical phenomena in emerging energy devices, including all-solid-state Li ion batteries (ASSLiBs), only when the results are analyzed in a consistent way without arbitrariness. This study1 aimed to establish such a robust analysis for ASSLiB cells using a fast lithium ion conductor Li10 +x Ge1+x P2 −x S12 (LGPS)2, by applying distribution-of-relaxation time (DRT) analysis3. The DRT method distinctively visualized impedance changes depending on states of charge (SOCs). Pellet-type cells were prepared with an In–Li anode, LGPS separator, cathode composite comprising LGPS and LiNbO3-coated LiCoO2 powders4. Figure 1a shows the discharge curve that was recorded for the cell at the current density of 13.2 μA cm−2 (1/40 C-rate) and with the cut-off voltage of 1.9–3.6 V vs. Li+/In–Li (2.55–4.25 V vs. Li+/Li). The EIS measurements were performed during discharge process at various SOCs from 100% to 20%. Nyquist diagrams obtained from the EIS data are shown in Figure 1b, where two broad semicircles are observed at low and high frequency sides. This result indicates at least two electrochemical processes exist in the cell. Both semicircles become large in size upon decreasing SOCs from 100 % down to 20%, indicating that the cell has SOC-dependent electrochemical processes. Figure 1c shows DRT transformation of the EIS data, which helps to separate impedance components in detail. Here horizonal and vertical axes respectively represent the measurement frequency and polarization contribution at each frequency. The center frequency of each distinct peak corresponds to time constant [τ =1/(2πf)] for the respective electrochemical process, and thus the number of peaks matches that of electrochemical processes in the cell. Meanwhile, the peak area represents polarization contribution of each process. Consistently in the whole SOC range, the above DRT analysis indicates the semicircle at high frequency side is divided into two impedance contributions and that at low frequency side cannot be separated any more. This result is consistent with the DRT spectra from additionally prepared symmetric cells; in total three DRT peaks were observed with two peaks from interphase and interface between In–Li/LGPS, and one from LiNbO3-coated LiCoO2/LGPS interface. Accordingly, DRT diagram in Figure 1c was interpreted as indicated by arrows for each peak. This study demonstrated that DRT analysis supports a consistent interpretation of EIS data from ASSLiB cells at various SOCs and with different electrode configurations, and thus implied that the method will also help subsequent equivalent circuit model analysis for reproducible parametrization of electrochemical processes.1. S. Hori et al., “Understanding the impedance spectra of all-solid-state lithium battery cells with sulfide superionic conductors,” J. Power Sources 556, 232450 (2023).2. N. Kamaya et al., “A lithium superionic conductor,” Nat. Mater. 10, 682–686 (2011).3. S. Dierickx, A. Weber, E. Ivers-Tiffée, “How the distribution of relaxation times enhances complex equivalent circuit models for fuel cells,” Electrochim. Acta 355, 136764 (2020).4. N. Ohta et al., “LiNbO3-coated LiCoO2 as cathode material for all solid-state lithium secondary batteries,” Electrochem. Commun. 9, 1486-1490 (2007). Figure 1

Unveiling Challenges and Opportunities in Silicon-Based All-Solid-State Batteries: Thin-Film Bonding with Mismatch Strain.

Li-metal and silicon are potential anode materials in all-solid-state Li-ion batteries (ASSBs) due to high specific capacity. However, both materials form gaps at the interface with solid electrolytes (SEs) during charging/discharging, resulting in increased impedance and uneven current density distribution. In this perspective, the different mechanisms of formation of these gaps are elaborated in detail. For Li-metal anodes, Li-ions are repeatedly stripped and unevenly deposited on the surface, leading to gaps and Li dendrite formation, which is an unavoidable electrochemical behavior. For Si-based anodes, Li-ions inserting/extracting within the Si-based electrode causes volume changes and a local separation from the SE, which is a mechanical behavior and avoidable by mitigating the strain mismatch of thin-film bonding between anode and SE. Si electro-chemical-mechanical behaviors are also described and strategies recommended to synergistically decrease Si-based electrode strain, including Si materials, Si-based composites, and electrodes. Last, it is suggested to choose a composite polymer-inorganic SE with favorable elastic properties and high ionic conductivity and form it directly on the Si-based electrode, beneficial for increasing SE strain to accommodate stack pressure and the stability of the interface. Thus, this perspective sheds light on the development and application of Si-based ASSBs.

A fully coupled mechano-electrochemical model for all-solid-state Li-ion batteries: An optimal strategy for controlling interfacial contact using internal stress generated by electrode expansion

A fully coupled electrochemical-mechanical model of all-solid-state Li-ion batteries (ASSLBs) considering the interfacial contact loss is established. The influences of current and partial molar volume of cathode/anode on the interfacial contact and performance of the ASSLB are numerically studied. The results show that the range of stress changes within the ASSLB are dependent on the current applied. Lithium (Li) partially inserted into anode cannot return to cathode during discharging, which causes a “residual stress” and then can improves the interface contact. The interfacial contact loss gives rise to an increase in local current density. Cycling with a current density of 0.2 mA cm−2, the local current density across the electrode/electrolyte interface is as high as 0.66 mA cm−2, which increases risks such as dendrite formation. We further show that a large partial molar volume of cathode/anode may directly reduce the capacity retention. Moreover, higher partial molar volume of cathode or lower that of anode reduces the (stack) stress, which can deteriorate the interface contact area. Finally, the cathode materials with lower partial molar volume are recommend to balance capacity and interfacial contact. As for anodes, the moderate partial molar volumes are required for robust ASSLBs with improved performance characteristics.

Mechanochemical reactions between polyanionic borate and residue Li2CO3 on LiCoO2 to stabilize cathode/electrolyte interface in sulfide-based all-solid-state batteries

Sulfide-based all-solid-state Li-ion batteries (ASSLIBs) are recognized as promising next-generation batteries, due to its advantage of high energy density, high safety and high Li+ diffusivity in sulfide solid electrolytes (SEs). However, interfacial instability between cathode (like LiCoO2) and sulfide SEs hinders its commercial applications. Herein, a simple mechanochemical strategy, which mechanically mixed polyanionic borate precursor and Li2CO3 residue on LiCoO2 (LCO) cathode with subsequent thermochemical reactions, was proposed to achieve analogous “solid electrolyte interphase (SEI)” to address such issues. The artificial SEI consists of crystalline LiBa(B3O5)3 (LBBO), Li3BO3 (LBO) and amorphous lithium boron oxide (Li-B-O). Therein, the former two endow high interfacial stability with SEs and ionic conductivity respectively, while the latter presented in the former interspace isolated the LCO cathode from Li10GeP2S12 (LGPS) solid electrolyte and constructed a continuous interlayer with LBBO and LBO. According to the phase diagram and direct observation through TEM, it is confirmed that a suitable ratio of raw LBBO precursor and Li2CO3 residue can realize an appropriate proportion of LBO to balance the interfacial stability and the diffusion of Li+ in obtained artificial interlayer, which enables high cyclability and rate performance in LCO/LGPS/Li-In ASSLIBs. Specifically, SEI with 9.4 mol.% LBO boosts an initial discharge capacity of 153.8 mAh g−1 (2.6–4.3 V (vs. Li/Li+), 0.1 C) with 74.4 % retention (150 cycles) and an excellent rate capability of 92.9 and 56.1 mAh g−1 at 1 C and 2 C respectively. Upon increased cut-off voltage of 4.5 V, an initial 167.3 mAh g−1 capacity (0.2 C) and 64.7 % retention (150 cycles) can also be achieved. The present strategy utilizing mechanochemical reactions between polyanionic borate and Li2CO3 residue to construct analogous SEI will offer fresh insights to stabilize the electrode/electrolyte interface of ASSLIBs derived from diverse polyanionic-type borates or phosphates, which can be widely used in other all-solid-state batteries with various cathodes and electrolytes.

Computational design of a mixed A-site cation halide solid electrolyte for all-solid-state lithium batteries

All-solid-state Li-ion batteries (ASSBs) are considered as ideal next-generation energy storage devices owing to their safe operation and high energy densities.

Interfacial contact loss and bending effects on electrochemical-mechanical modeling for all-solid-state Li-ion batteries

All-solid-state Li-ion batteries (ASSLBs) are ideal power sources for the future electric vehicle and energy storage industries, but electrodes/solid-electrolytes (SE) interface issues and mechanical flexibility are emerging as the major limitation to the development of ASSLBs. In this paper, a flexible thin-film ASSLB composed of NMC811 cathode, SiC anode, and LGPS solid-electrolyte is studied. An interfacial contact model and a coupled electrochemical-mechanical model of the ASSLB with bending effects are developed by numerical solution. The results show that bending effects can alleviate the interfacial stress which occurs during lithiation. In addition, external pressure, a smoother interface and a softer solid electrolyte can effectively improve the actual contact area. To investigate the effects of contact factors and curvature on the cell potential, a complete charge-discharge cycle is simulated. It is found that increasing the curvature and contact factor can delay the time to reach the cut-off voltage which increases the cell capacity. The curvature mainly affects the electrolyte potential while the contact coefficient mainly affects the overpotential. Taken together, this study explains the effects of curvature and contact loss on the mechanical and electrochemical behavior of ASSLBs, and provides theoretical guidance for improving the interface design and enhancing cell stability.

A Fully Coupled Mechano-Electrochemical Model for All-Solid-State Thin-Film Li-Ion Batteries with Non-Porous Electrodes: Effects of Chemo-Mechanical Expansions on Battery Performance and Optimization Strategies for Stress Evolution

A comprehensive and novel mechano-electrochemical coupling model for all-solid-state Li-ion batteries (ASSLBs) is developed, in particular, focusing on the influence of the volume changes caused by ions redistribution in the electrodes on the electrical and mechanical properties of the battery. The mathematical relationship between the partial molar volume and Poisson’s ratio is determined for the condition of zero stress. The roles of the partial molar volumes of cathode and anode, the thickness and Young’s modulus of the spacer are investigated. The results show that the electrode volume changes significantly during the charging and discharging process. Due to the mechanical imbalance, the confined cell generates considerable compressive stress (approximately 0.6 MPa). Reducing the partial molar volume of the anode can not only eliminate the compression stress but augment the capacity. Note that for the ASSLBs containing inorganic (oxide or sulfide) solid electrolytes (SEs), adjusting the material parameters to obtain proper compressive stress instead of a bulky cell holder may be another useful method to overcome the poor interface contact. Finally, by introducing polyurethane foam or other soft blocks with a suitable thickness and Young’s modulus as spacers, the stress of the cell can be reduced by 79.33%.

Theoretical insights into interfacial stability and ionic transport of Li2OHBr solid electrolyte for all-solid-state batteries.

Li-rich antiperovskite materials are promising candidates as inorganic solid electrolytes (ISEs) for all-solid-state Li-ion batteries (ASSLIBs). However, the material faces several pressing issues for its application, concerning the phase stability and electrochemical stability of the synthesized material and the Li-ion transport mechanism in it. Herein, we performed first-principles computational studies on the phase stability, interfacial stability, defect chemistry, and electronic/ionic transport properties of Li2OHBr material. The calculation results show that the Li2OHBr is thermodynamically metastable at 0 K and can be synthesized experimentally. This material exhibits a wider intrinsic electrochemical stability window (0.80-3.15 V) compared with sulfide solid electrolytes. Moreover, the Li2OHBr displays significant chemical stability when in contact with typical cathode materials (LiCoO2, LiMn2O4, LiFePO4) and moisture. The dominant defects of Li2OHBr are predicted to be VLi- and Lii +, corresponding to lower Li-ion migration barriers of 0.38 and 0.49 eV, respectively, while the replacement of some of the OH- by F- is shown to be effective in decreasing migration barriers in Li2OHBr. These findings provide a theoretical framework for further designing high performance ISEs.

Computational Investigation of the Interfacial Stability of Lithium Chloride Solid Electrolytes in All-Solid-State Lithium Batteries.

All-solid-state Li-ion batteries (ASSLIBs) with solid electrolytes (SEs) are promising next-generation batteries owing to their high energy density and high safety. Recently, lithium chloride SEs have attracted increasing attention because of their high ionic conductivity and broad electrochemical stability window. However, only a few studies have been reported for the application of lithium chloride SEs in high-energy ASSLIBs employing lithium metal anodes and high-voltage cathode materials. This study examines the interfacial stability of lithium chloride SEs toward lithium metal anodes and high-voltage cathode materials using first-principles calculations. Calculation results indicate the chemical instability of lithium chloride SEs toward lithium metal anodes. Metallic phases are formed by reduction reactions resulting in the continuous decomposition of lithium chloride SEs. In addition, lithium chloride SEs exhibit high reactivity toward high-voltage cathode materials, resulting in interfacial resistance by decomposition reactions. Computational screening is performed to explore coating materials to stabilize the interfaces, demonstrating that binary halides are appropriate for the anode and 54 compounds are discovered for the cathode. Among the coating materials for the cathode, several ternary oxides such as LiAl5O8, Li2MoO4, and LiTaO3 are found to be promising for enhancing the interfacial stability between lithium chloride SEs and high-voltage cathode materials.

Tough Polymer Electrolyte with an Intrinsically Stabilized Interface with Li Metal for All-Solid-State Lithium-Ion Batteries

A high-performance solid polymer electrolyte (SPE) membrane that simultaneously addresses the issues of enhanced toughness and Li-dendrite mitigation for all-solid-state Li-ion batteries (ASSLIBs) is demonstrated. The membrane has a sandwiched structure consisting of a center poly(ethylene oxide)/lithium bis(trifluoromethanesulfonyl) imide (PEO/LiTFSI) electrolyte matrix laminated on both sides with electrospun high-polarity β-phase poly(vinylidene fluoride-co-hexafluoropropylene) (β-PVDF-HFP) nanofibers. The nanofiber layers impart remarkable enhancement in both mechanical and electrochemical properties of the SPE, including a 20-fold increase in tensile strength and a 48-fold increase in toughness, along with up to 4-fold enhancement in Li-ionic conductivity. Moreover, the highly polar fluorinated nanofiber cladding layers enable a stable Li-plating/stripping interface on the Li anode to efficiently mitigate dendrite formation, while improving the electrochemical interfacial stability with the cathode. In a Li|SPE|Li symmetric cell, the use of the sandwiched SPE is demonstrated to improve the cycle stability from short-circuiting at 144 h for a pristine PEO/LiTFSI membrane to no short-circuiting even up to 3600 h (1800 Li-plating-stripping cycles). In an example of LiFePO4|SPE|Li ASSLIBs, using the sandwiched membrane enables substantial reduction irreversible capacity upon charging to the high-voltage end and more than 80% capacity retention for over 1600 h. This work presents a feasible and facile design for an SPE for high-performance ASSLIBs.

Extensively Reducing Interfacial Resistance by the Ultrathin Pt Layer between the Garnet-Type Solid-State Electrolyte and Li-Metal Anode.

All-solid-state Li-ion batteries (ASSLIBs), also known as next-generation batteries, have attracted much attention due to their high energy density and safety. The best advantage of ASSLIBs is the Li-metal anodes that could be used without safety issues. In this study, a highly conductive garnet solid electrolyte (Li6.75La3Zr1.75Ta0.25O12, LLZTO) was used in the ASSLIB, and a Pt film was used to modify the surface of LLZTO to prove the solution of the Li-metal anode for LLZTO. Li-Pt alloy was synthesized to improve the wettability and contact of the interface. The interfacial resistance was reduced by 21 times, at only 9 Ω cm2. The symmetric cell could stably cycle over 3500 h at a current density of 0.1 mA cm-2. The full cell of Li|Li-Pt|LLZTO|LiFePO4 and Li|Li-Pt|LLZTO|LiMn0.8Fe0.2PO4 achieved high stability in terms of battery performance. Point-to-point contact transformed into homogeneous surface contact made the Li-ion flux faster and more stable. This surface modification method could provide researchers with a new choice for fixing interface issues and promoting the application of high-performance ASSLIBs in the future.

One-Pot Green Synthesis of a PEO/TCPP/LiClO4 Solid Polymer Electrolyte with Improvement of Ion Transport

All-solid-state Li-ion batteries (ASSBs) composed of safe and reliable solid electrolyte materials have become increasingly important in energy storage systems. Poly(ethylene oxide) (PEO)-based electrolytes have been rapidly developed for ASSBs over recent years due to their nonflammability, shape flexibility, good interface contact with electrodes, and better electrochemical stability. Nevertheless, their low ionic conductivity remains a serious issue to be addressed urgently. Herein, we report a solid composite polymer electrolyte film with homogeneous network structures, which is composed of a LiClO4-added PEO-based polymer matrix plasticized with an additive meso-tetra (carboxyphenyl) porphyrin (TCPP), a kind of porphyrin covalent organic framework (COF) material, and obtained by a green and easy-to-scale solution-casting technique to improve the ionic conductivity and simplify the synthesis process. To the best of our knowledge, this is the first report on introducing TCPP into the PEO electrolyte. It demonstrates that the blending of PEO with TCPP can effectively suppress the PEO crystallinity and enhance the ion conductivity of the solid polymer electrolytes. As the content of TCPP reaches 8 wt %, it exhibits maximum ionic conductivities of 2.34 × 10–5 and 2.21 × 10–4 S cm–1 at 25 and 65 °C, respectively, which is about five times higher than that of the polymer reference electrolyte. It additionally brings an improved tLi+ value of 0.23 at room temperature with an electrochemical stability window of up to 5 V vs Li+/Li. In addition, when compared to the pure PEO film, a significant improvement in thermal stability is observed. This work may provide a new concept for building a new type of homogeneous COF-PEO-based composite polymer electrolyte film (CPE) that can be utilized as a desirable material in solid electrolytes for lithium-ion battery applications.

An all coupled electrochemical-mechanical model for all-solid-state Li-ion batteries considering the effect of contact area loss and compressive pressure

A fully coupled electrochemical-mechanical theoretical model for all-solid-state Li-ion batteries (ASSLBs) is established considering the effects of contact areas and compressive pressure. The influences of contact area loss and compressive pressure on the electrical and mechanical properties of the ASSLB are numerically studied in the charging process. The results indicate that the loss of contact area may result in poor electrical performance. The contact area loss of cathode/SE interface can lead to the lithium concentration reaching the minimum value earlier, which brings about the decreases of both voltage and capacity, while that of anode/SE interface enables the ASSLB to attain the charging cut-off voltage in advance. Therefore, a lower capacity of ASSLB is found. The battery performance can be reduced for both higher (more than 1 MPa) and lower (0.05–0.4 MPa) compressive pressures, while the optimal charging performance can be obtained for medium (0.4–1 MPa) compressive pressures. Meanwhile, the stress-drop at the electrode/SE interfaces can reach the minimum. The charge and discharge experiments with 0.4 MPa compressive pressure are carried out. The maximum error between the experimental results and simulation results is 8.12%, which verified the accuracy of the simulated method.