Nacre-Inspired Composite Electrolytes for Load-Bearing Solid-State Lithium-Metal Batteries

Solid-state lithium-metal batteries with solid electrolytes are promising for next-generation energy-storage devices. However, it remains challenging to develop solid electrolytes that are both mechanically robust and strong against external mechanical load, due to the brittleness of ceramic electrolytes and the softness of polymer electrolytes. Herein, a nacre-inspired design of ceramic/polymer solid composite electrolytes with a “brick-and-mortar” microstructure is proposed. The nacre-like ceramic/polymer electrolyte (NCPE) simultaneously possesses a much higher fracture strain (1.1%) than pure ceramic electrolytes (0.13%) and a much larger ultimate flexural modulus (7.8 GPa) than pure polymer electrolytes (20 MPa). The electrochemical performance of NCPE is also much better than pure ceramic or polymer electrolytes, especially under mechanical load. A 5 × 5 cm² pouch cell with LAGP/poly(ether-acrylate) NCPE exhibits stable cycling with a capacity retention of 95.6% over 100 cycles at room temperature, even undergoes a large point load of 10 N. In contrast, cells based on pure ceramic and pure polymer electrolyte show poor cycle life. The NCPE provides a new design for solid composite electrolyte and opens up new possibilities for future solid-state lithium-metal batteries and structural energy storage.     

Development of an Electrophoretic Deposition Method for the In Situ Fabrication of Ultra-Thin Composite-Polymer Electrolytes for Solid-State Lithium-Metal Batteries

All-solid-state lithium-metal batteries offer higher energy density and safety than lithium-ion batteries, but their practical applications have been pushed back by the sluggish Li⁺ transport, unstable electrolyte/electrode interface, and/or difficult processing of their solid-state electrolytes. Li⁺-conducting composite polymer electrolytes (CPEs) consisting of sub-micron particles of an oxide solid-state electrolyte (OSSE) dispersed in a solid, flexible polymer electrolyte (SPE) have shown promises to alleviate the low Li⁺ conductivity of SPE, and the high rigidity and large interfacial impedance of OSSEs. Solution casting has been by far the most widely used procedure for the preparation of CPEs in research laboratories; however, this method imposes several drawbacks including particle aggregation and settlement during a long-term solvent evaporation step, excessive use of organic solvents, slow production time, and mechanical issues associated with handling of ultra-thin films of CPEs (<50 µm). To address these challenges, an electrophoretic deposition (EPD) method is developed to in situ deposit ultra-thin CPEs on lithium-iron-phosphate (LFP) cathodes within just a few minutes. EPD-prepared CPEs have shown better electrochemical performance in the lithium-metal battery than those CPEs prepared by solution casting due to a better dispersion of OSSE within the SPE matrix and improved CPE contact with LFP cathodes.     

Hollow-Particles Quasi-Solid-State Electrolytes with Biomimetic Ion Channels for High-Performance Lithium-Metal Batteries

Solid-state electrolytes (SSEs) are the core material of solid-state lithium metal batteries (SLMBs), which are being researched urgently owing to their high energy and safety. Both high ionic conductivity and excellent cycling stability remain the primary goal of solid-state electrolytes. Herein, inspired by K⁺/Na⁺ ion channels in cell membrane of eukaryotes, a novel hollow UiO-66 with biomimetic ion channels based on quasi-solid-state electrolytes (QSSEs) is designed. The hollow UiO-66 spheres containing biomimetic ion channels can spontaneously combine anions and incorporate more lithium ions, creating improved ionic conductivity (1.15 × 10⁻³ S cm⁻¹) and lithium-ion transference number (0.70) at room temperature. The long-term cycling of symmetric batteries and COMSOL simulations demonstrate that this biomimetic strategy enables uniform ion flux to suppress Li dendrites. Furthermore, the Li metal full cells paired with LiFePO₄ cathode exhibit excellent cycling stability and rate performance. Consequently, the strategy of designing biomimetic QSSEs opens up a new path for developing high-performance electrolytes for SLMBs.     

Computation-Guided Synthesis of New Garnet-Type Solid-State Electrolytes via an Ultrafast Sintering Technique

The discovery of new solid-state electrolytes (SSEs) can be guided by computation for next-generation Li batteries toward higher energy density and better safety. However, conventional synthetic methods often suffer from severe loss of Li and poor material quality, therefore preventing the promise of the predicted SSE candidates to be realized. In this study, computationally predicted SSEs with desirable material quality are synthesized via an ultrafast sintering technique. Three new garnet-type Li⁺ conductors, including Li_6.5Nd₃Zr_1.5Ta_0.5O₁₂ (LNZTO), Li_6.5Sm₃Zr_1.5Ta_0.5O₁₂ (LSZTO), and Li_6.5(Sm_0.5La_0.5)₃Zr_1.5Ta_0.5O₁₂ (L-LSZTO), are screened by density functional theory to exhibit good synthesizability and stability. The ultrafast sintering method by Joule heating effectively shorten the sintering time from several hours to <25 s, thereby reducing the Li loss and effectively merging the grains toward high material quality. In agreement with the computational prediction, LNZTO demonstrates the best synthesizability and phase stability, thereby achieving the highest conductivity of 2.3 × 10⁻⁴ S cm⁻¹ among the three new SSE candidates. Using a current density of 0.2 mA cm⁻², the Li/LNZTO/Li symmetric cell can cycle for ≈90 h without obvious increase of overpotentials. This study showcases the successful realization of computational predictions by the ultrafast sintering technique for the rapid optimization and screening of high-performance SSEs.     

Thiol-Branched Solid Polymer Electrolyte Featuring High Strength,Toughness, and Lithium Ionic Conductivity for Lithium-Metal Batteries

Lithium-metal batteries (LMBs) with high energy densities are highly desirable for energy storage, but generally suffer from dendrite growth and side reactions in liquid electrolytes; thus the need for solid electrolytes with high mechanical strength, ionic conductivity, and compatible interface arises. Herein, a thiol-branched solid polymer electrolyte (SPE) is introduced featuring high Li⁺ conductivity (2.26 × 10⁻⁴ S cm⁻¹ at room temperature) and good mechanical strength (9.4 MPa)/toughness (≈500%), thus unblocking the tradeoff between ionic conductivity and mechanical robustness in polymer electrolytes. The SPE (denoted as M-S-PEGDA) is fabricated by covalently cross-linking metal–organic frameworks (MOFs), tetrakis (3-mercaptopropionic acid) pentaerythritol (PETMP), and poly(ethylene glycol) diacrylate (PEGDA) via multiple C S C bonds. The SPE also exhibits a high electrochemical window (>5.4 V), low interfacial impedance (<550 Ω), and impressive Li⁺ transference number (t_Li+ = 0.44). As a result, Li||Li symmetrical cells with the thiol-branched SPE displayed a high stability in a >1300 h cycling test. Moreover, a Li|M-S-PEGDA|LiFePO₄ full cell demonstrates discharge capacity of 143.7 mAh g⁻¹ and maintains 85.6% after 500 cycles at 0.5 C, displaying one of the most outstanding performances for SPEs to date.     

Lithiophilic Magnetic Host Facilitates Target-Deposited Lithium for Practical Lithium-Metal Batteries

Lithium-metal shows promising prospects in constructing various high-energy-density lithium-metal batteries (LMBs) while long-lasting tricky issues including the uncontrolled dendritic lithium growth and infinite lithium volume expansion seriously impede the application of LMBs. In this work, it is originally found that a unique lithiophilic magnetic host matrix (Co₃O₄-CCNFs) can simultaneously eliminate the uncontrolled dendritic lithium growth and huge lithium volume expansion that commonly occur in typical LMBs. The magnetic Co₃O₄ nanocrystals which inherently embed on the host matrix act as nucleation sites and can also induce micromagnetic field and facilitate a targeted and ordered lithium deposition behavior thus, eliminating the formation of dendritic Li. Meanwhile, the conductive host can effectively homogenize the current distribution and Li-ion flux, thus, further relieving the volume expansion during cycling. Benefiting from this, the featured electrodes demonstrate ultra-high coulombic efficiency of 99.1% under 1 mA cm⁻² and 1 mAh cm⁻². Symmetric cell under limited Li (10 mAh cm⁻²) inspiringly delivers ultralong cycle life of 1600 h (under 2 mA cm⁻², 1 mAh cm⁻²). Moreover, LiFePO₄||Co₃O₄-CCNFs@Li full-cell under practical condition of limited negative/positive capacity ratio (2.3:1) can deliver remarkably improved cycling stability (with 86.6% capacity retention over 440 cycles).     

High-Safety and High-Energy-Density Lithium Metal Batteries in a Novel Ionic-Liquid Electrolyte

Rechargeable lithium metal batteries are next generation energy storage devices with high energy density, but face challenges in achieving high energy density, high safety, and long cycle life. Here, lithium metal batteries in a novel nonflammable ionic-liquid (IL) electrolyte composed of 1-ethyl-3-methylimidazolium (EMIm) cations and high-concentration bis(fluorosulfonyl)imide (FSI) anions, with sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) as a key additive are reported. The Na ion participates in the formation of hybrid passivation interphases and contributes to dendrite-free Li deposition and reversible cathode electrochemistry. The electrolyte of low viscosity allows practically useful cathode mass loading up to ≈16 mg cm⁻². Li anodes paired with lithium cobalt oxide (LiCoO₂) and lithium nickel cobalt manganese oxide (LiNi_0.8Co_0.1Mn_0.1O₂, NCM 811) cathodes exhibit 99.6–99.9% Coulombic efficiencies, high discharge voltages up to 4.4 V, high specific capacity and energy density up to ≈199 mAh g⁻¹ and ≈765 Wh kg⁻¹ respectively, with impressive cycling performances over up to 1200 cycles. Highly stable passivation interphases formed on both electrodes in the novel IL electrolyte are the key to highly reversible lithium metal batteries, especially for Li–NMC 811 full batteries.     

Shaping the Future of Solid-State Electrolytes through Computational Modeling

Advances and progress in computational research that aims to understand and improve solid-state electrolytes (SSEs) are outlined. One of the main challenges in the development of all-solid-state batteries is the design of new SSEs with high ion diffusivity that maintain chemical and phase stability and thereby provide a wide electrochemical stability window. Solving this problem requires a deep understanding of the diffusion mechanism and properties of the SSEs. A second important challenge is the development of an understanding of the interface between the SSE and the electrode. The role of molecular simulations and modeling in dealing with these challenges is discussed, with reference to examples in the literature. The methods used and issues considered in recent years are highlighted. Finally, a brief outlook about the future of modeling in studying solid-state battery technology is presented.     

锂离子电池用有机电解液和聚合物电解质的研究进展

从导电锂盐、有机溶剂和添加剂三个方面详细综述了锂离子电池用有机电解液的研究进展。同时针对聚合物电解质的组成、结构和性能的差异,将其分为四类,阐述了它们的优缺点及其在锂离子电池中的应用与研究进展。最后展望了电解质的发展前景。     

Tape-Casting Li0.34La0.56TiO3 Ceramic Electrolyte Films Permit High Energy Density of Lithium-Metal Batteries

Ceramic oxide electrolytes are outstanding due to their excellent thermostability, wide electrochemical stable windows, superior Li-ion conductivity, and high elastic modulus compared to other electrolytes. To achieve high energy density, all-solid-state batteries require thin solid-state electrolytes that are dozens of micrometers thick due to the high density of ceramic electrolytes. Perovskite-type Li_0.34La_0.56TiO₃ (LLTO) freestanding ceramic electrolyte film with a thickness of 25 µm is prepared by tape-casting. Compared to a thick electrolyte (>200 µm) obtained by cold-pressing, the total Li ionic conductivity of this LLTO film improves from 9.6 × 10⁻⁶ to 2.0 × 10⁻⁵ S cm⁻¹. In addition, the LLTO film with a thickness of 25 µm exhibits a flexural strength of 264 MPa. An all-solid-state Li-metal battery assembled with a 41 µm thick LLTO exhibits an initial discharge capacity of 145 mAh g⁻¹ and a high capacity retention ratio of 86.2% after 50 cycles. Reducing the thickness of oxide ceramic electrolytes is crucial to reduce the resistance of electrolytes and improve the energy density of Li-metal batteries.     

Research Progresses of Liquid Electrolytes in Lithium-Ion Batteries

In recent years, the rapid development of modern society is calling for advanced energy storage to meet the growing demands of energy supply and generation. As one of the most promising energy storage systems, secondary batteries are attracting much attention. The electrolyte is an important part of the secondary battery, and its composition is closely related to the electrochemical performance of the secondary batteries. Lithium-ion battery electrolyte is mainly composed of solvents, additives, and lithium salts, which are prepared according to specific proportions under certain conditions and according to the needs of characteristics. This review analyzes the advantages and current problems of the liquid electrolytes in lithium-ion batteries (LIBs) from the mechanism of action and failure mechanism, summarizes the research progress of solvents, lithium salts, and additives, analyzes the future trends and requirements of lithium-ion battery electrolytes, and points out the emerging opportunities in advanced lithium-ion battery electrolytes development.     

Influence of Lithium Diffusion into Copper Current Collectors on Lithium Electrodeposition in Anode-Free Lithium-Metal Batteries

The development of “anode-free” lithium-metal batteries with high energy densities is, at present, mainly limited by the poor control of the nucleation of lithium directly on the copper current collector, especially in conventional carbonate electrolytes. It is therefore essential to improve the understanding of the lithium nucleation process and its interactions with the copper substrate. In this study, it is shown that diffusion of lithium into the copper substrate, most likely via the grain boundaries, can significantly influence the nucleation process. Such diffusion makes it more difficult to obtain a great number of homogeneously distributed lithium nuclei on the copper surface and thus leads to inhomogeneous electrodeposition. It is, however, demonstrated that the nucleation of lithium on copper is significantly improved if an initial chemical prelithiation of the copper surface is performed. This prelithiation saturates the copper surface with lithium and hence decreases the influence of lithium diffusion via the grain boundaries. In this way, the lithium nucleation can be made to take place more homogenously, especially when a short potentiostatic nucleation pulse that can generate a large number of nuclei on the surface of the copper substrate is applied.     

锂离子电池聚合物电解质研究进展

综述了二次锂离子电池聚合物电解质的最新研究进展,对不同类型的聚合物电解质按其基体进行分类,包括常见的几种聚合物基体以及近年来发展起来的几种新型聚合物基体。对于每类基体相关的研究成果,主要关注的是电化学性能。对一些性能优异的聚合物电解质体系及其相应的制备方法,给出了较为全面的概述。与使用液体有机电解质的二次锂离子电池相比...     

Extended Electrochemical Window of Solid Electrolytes via Heterogeneous Multilayered Structure for High‐Voltage Lithium Metal Batteries

In response to the call for safer high‐energy‐density storage systems, high‐voltage solid‐state Li metal batteries have attracted extensive attention. Therefore, solid electrolytes are required to be stable against both Li anode and high‐voltage cathodes; nevertheless, the requirements still cannot be completely satisfied. Herein, a heterogeneous multilayered solid electrolyte (HMSE) is proposed to broaden electrochemical window of solid electrolytes to 0–5 V, through different electrode/electrolyte interfaces to overcome the interfacial instability problems. Oxidation‐resistance poly(acrylonitrile) (PAN) is in contact with the cathode, while reduction tolerant polyethylene glycol diacrylate contacts with Li metal anode. A Janus and flexible PAN@Li_1.4Al_0.4Ge_1.6(PO₄)₃ (80 wt%) composite electrolyte is designed as intermediate layer to inhibit dendrite penetration and ensure compact interface. Paired with LiNi_0.6Co_0.2Mn_0.2O₂ and LiNi_0.8Co_0.1Mn_0.1O₂ cathodes, which are rarely used in solid‐state batteries, the solid‐state Li metal batteries with HMSE exhibit excellent electrochemical performance including high capacity and long cycle life. Besides, the Li||Li symmetric batteries maintain a stable polarization less than 40 mV for more than 1000 h under 2 mA cm^?2 and effective inhibition of dendrite formation. This study offers a promising approach to extend the applications of solid electrolytes for high‐voltage solid‐state Li metal batteries.     

A Self-Healing Amalgam Interface in Metal Batteries

Poor cyclability and safety concerns caused by the uncontrollable dendrite growth and large interfacial resistance severely restrict the practical applications of metal batteries. Herein, a facile, universal strategy to fabricate ceramic and glass phase compatible, and self-healing metal anodes is proposed. Various amalgam-metal anodes (Li, Na, Zn, Al, and Mg) show a long cycle life in symmetric cells. It has been found that liquid Li amalgam shows a complete wetting with the surface of lanthanum lithium titanate electrolyte and a glass-phase solid-state electrolyte. The interfacial compatibility between the lithium metal anode and solid-state electrolyte is dramatically improved by using an in situ regenerated amalgam interface with high electron/ion dual-conductivity, obviously decreasing the anode/electrolyte interfacial impedance. The lithium-amalgam interface between the metal anode and electrolyte undergoes a reversible isothermal phase transition between solid and liquid during the cycling process at room temperature, resulting in a self-healing surface of metal anodes.     

Toward High-Energy-Density Lithium Metal Batteries: Opportunities and Challenges for Solid Organic Electrolytes

With increasing demands for safe, high capacity energy storage to support personal electronics, newer devices such as unmanned aerial vehicles, as well as the commercialization of electric vehicles, current energy storage technologies are facing increased challenges. Although alternative batteries have been intensively investigated, lithium (Li) batteries are still recognized as the preferred energy storage solution for the consumer electronics markets and next generation automobiles. However, the commercialized Li batteries still have disadvantages, such as low capacities, potential safety issues, and unfavorable cycling life. Therefore, the design and development of electromaterials toward high-energy-density, long-life-span Li batteries with improved safety is a focus for researchers in the field of energy materials. Herein, recent advances in the development of novel organic electrolytes are summarized toward solid-state Li batteries with higher energy density and improved safety. On the basis of new insights into ionic conduction and design principles of organic-based solid-state electrolytes, specific strategies toward developing these electrolytes for Li metal anodes, high-energy-density cathode materials (e.g., high voltage materials), as well as the optimization of cathode formulations are outlined. Finally, prospects for next generation solid-state electrolytes are also proposed.     

A Universal Room-Temperature 3D Printing Approach Towards porous MOF Based Dendrites Inhibition Hybrid Solid-State Electrolytes

Hybrid solid-state electrolytes (HSSEs) provide new opportunities and inspiration for the realization of safer, higher energy-density metal batteries. The innovative application of 3‑dimensional printing in the electrochemical field, especially in solid-state electrolytes, endows energy storage devices with fascinating characteristics. In this paper, effective dendrite-inhibited PEO/MOFs HSSEs is innovatively developed through universal room-temperature 3‑dimensional printing (RT-3DP) strategy. The prepared HSSEs display enhanced dendrite inhibition due to the porous MOF filler promoting homogeneity of lithium deposition and the formation of C-OCO₃Li, ROLi, LiF mesophases, which further improve the migration of Li⁺ in PEO chain and comprehensive performances. This universal strategy realizes the fabrication of different slurry components (PEO with ZIF-67, MOF-74, UIO-66, ZIF-8 fillers) HSSEs at RT environment, providing new inspirations for the exploration of next-generation advanced solid-state batteries.     

Surface Oxygen Vacancy Inducing Li-Ion-Conducting Percolation Network in Composite Solid Electrolytes for All-Solid-State Lithium-Metal Batteries

Composite solid electrolytes (CSEs) are newly emerging components for all-solid-state Li-metal batteries owing to their excellent processability and compatibility with the electrodes. Moreover, the ionic conductivity of the CSEs is one order of magnitude higher than the solid polymer electrolytes (SPEs) by incorporation of inorganic fillers into SPEs. However, their advancement has come to a standstill owing to unclear Li-ion conduction mechanism and pathway. Herein, the dominating effect of the oxygen vacancy (O_vac) in the inorganic filler on the ionic conductivity of CSEs is demonstrated via Li-ion-conducting percolation network model. Based on density functional theory, indium tin oxide nanoparticles (ITO NPs) are selected as inorganic filler to determine the effect of O_vac on the ionic conductivity of the CSEs. Owing to the fast Li-ion conduction through the O_vac inducing percolation network on ITO NP–polymer interface, LiFePO₄/CSE/Li cells using CSEs exhibit a remarkable capacity in long-term cycling (154 mAh g⁻¹ at 0.5C after 700 cycles). Moreover, by modifying the O_vac concentration of ITO NPs via UV-ozone oxygen-vacancy modification, the ionic conductivity dependence of the CSEs on the surface O_vac from the inorganic filler is directly verified.     

Advances in the Design of 3D-Structured Electrode Materials for Lithium-Metal Anodes

Although the lithium-metal anode (LMA) can deliver a high theoretical capacity of ≈ 3860 mAh g⁻¹ at a low redox potential of − 3.040 V (vs the standard hydrogen electrode), its application in rechargeable batteries is hindered by the poor Coulombic efficiency and safety issues caused by dendritic metal growth. Consequently, careful electrode design, electrolyte engineering, solid-electrolyte interface control, protective layer introduction, and other strategies are suggested as possible solutions. In particular, one should note the great potential of 3D-structured electrode materials, which feature high active specific surface areas and stereoscopic structures with multitudinous lithiophilic sites and can therefore facilitate rapid Li-ion flux and metal nucleation as well as mitigate Li dendrite formation through the kinetic control of metal deposition even at high local current densities. This progress report reviews the design of 3D-structured electrode materials for LMA according to their categories, namely 1) metal-based materials, 2) carbon-based materials, and 3) their hybrids, and allows the results obtained under different experimental conditions to be seen at a single glance, thus being helpful for researchers working in related fields.