Ultrathin,Flexible Polymer Electrolyte for Cost‐Effective Fabrication of All‐Solid‐State Lithium Metal Batteries

All‐solid‐state batteries are promising candidates for the next‐generation safer batteries. However, a number of obstacles have limited the practical application of all‐solid‐state Li batteries (ASSLBs), such as moderate ionic conductivity at room temperature. Here, unlike most of the previous approaches, superior performances of ASSLBs are achieved by greatly reducing the thickness of the solid‐state electrolyte (SSE), where ionic conductivity is no longer a limiting factor. The ultrathin SSE (7.5 µm) is developed by integrating the low‐cost polyethylene separator with polyethylene oxide (PEO)/Li‐salt (PPL). The ultrathin PPL shortens Li⁺ diffusion time and distance within the electrolyte, and provides sufficient Li⁺ conductance for batteries to operate at room temperature. The robust yet flexible polyethylene offers mechanical support for the soft PEO/Li‐salt, effectively preventing short‐circuits even under mechanical deformation. Various ASSLBs with PPL electrolyte show superior electrochemical performance. An initial capacity of 135 mAh g^?1 at room temperature and the high‐rate capacity up to 10 C at 60 °C can be achieved in LiFePO₄/PPL/Li batteries. The high‐energy‐density sulfur cathode and MoS₂ anode employing PPL electrolyte also realize remarkable performance. Moreover, the ASSLB can be assembled by a facile process, which can be easily scaled up to mass production.     

Enabling High‐Energy Solid‐State Batteries with Stable Anode Interphase by the Use of Columnar Silicon Anodes

All‐solid‐state batteries (ASSBs) with silicon anodes are promising candidates to overcome energy limitations of conventional lithium‐ion batteries. However, silicon undergoes severe volume changes during cycling leading to rapid degradation. In this study, a columnar silicon anode (col‐Si) fabricated by a scalable physical vapor deposition process (PVD) is integrated in all‐solid‐state batteries based on argyrodite‐type electrolyte (Li₆PS₅Cl, 3 mS cm^?1) and Ni‐rich layered oxide cathodes (LiNi_0.9Co_0.05Mn_0.05O₂, NCM) with a high specific capacity (210 mAh g^?1). The column structure exhibits a 1D breathing mechanism similar to lithium, which preserves the interface toward the electrolyte. Stable cycling is demonstrated for more than 100 cycles with a high coulombic efficiency (CE) of 99.7–99.9% in full cells with industrially relevant areal loadings of 3.5 mAh cm^?2, which is the highest value reported so far for ASSB full cells with silicon anodes. Impedance spectroscopy revealed that anode resistance is drastically reduced after first lithiation, which allows high charging currents of 0.9 mA cm^?2 at room temperature without the occurrence of dendrites and short circuits. Finally, in‐operando monitoring of pouch cells gave valuable insights into the breathing behavior of the solid‐state cell.     

Solid‐State Prelithiation Enables High‐Performance Li‐Al‐H Anode for Solid‐State Batteries

Lithium alanates exhibit high theoretical specific capacities and appropriate lithiation/delithiation potentials, but suffer from poor reversibility, cycling stability, and rate capability due to their sluggish kinetics and extensive side reactions. Herein, a novel and facile solid‐state prelithiation approach is proposed to in situ prepare a Li₃AlH₆‐Al nanocomposite from a short‐circuited electrochemical reaction between LiAlH₄ and Li with the help of fast electron and Li‐ion conductors (C and P6₃mc LiBH₄). This nanocomposite consists of dispersive Al nanograins and an amorphous Li₃AlH₆ matrix, which enables superior electrochemical performance in solid‐state cells, as much higher specific capacity (2266 mAh g^?1), Coulombic efficiency (88%), cycling stability (71% retention in the 100th cycle), and rate capability (1429 mAh g^?1 at 1 A g^?1) are achieved. In addition, this nanocomposite works well in the solid‐state full cell with LiCoO₂ cathode, demonstrating its promising application prospects. Mechanism analysis reveals that the dispersive Al nanograins and amorphous Li₃AlH₆ matrix can dramatically enhance the lithiation and delithiation kinetics without side reactions, which is mainly responsible for the excellent overall performance. Moreover, this solid‐state prelithiation approach is general and can also be applied to other Li‐poor electrode materials for further modification of their electrochemical behavior.     

High‐Capacity All‐Solid‐State Sodium Metal Battery with Hybrid Polymer Electrolytes

All‐solid‐state sodium metal batteries (SSMBs) are of great interest for their high theoretical capacity, nonflammability, and relatively low cost owing partially to the abundance of sodium recourses. However, it is challenging to fabricate SSMBs because compared with their counterparts, which contain lithium metal, sodium metal is mechanically softer and more reactive toward the electrolyte. Herein, the synthesis and electrochemical properties of newly designed sodium‐containing hybrid network solid polymer electrolytes (SPEs) and their application in SSMBs are reported. The hybrid network is synthesized by controlled crosslinking of octakis(3‐glycidyloxypropyldimethylsiloxy)octasilsesquioxane and amine‐terminated polyethylene glycol in existence with sodium perchlorate (NaClO₄). Plating and stripping experiments using symmetric cells show prolonged cycle life of the SPEs, >5150 and 3550 h at current density of 0.1 and 0.5 mA cm^?2, respectively. The results for the first time show that the SPE|sodium metal interface migrates into the SPE phase upon cycling. SSMBs fabricated with the hybrid SPE sandwiched between sodium metal anode and bilayered δ‐Na_xV₂O₅ cathode exhibit record‐high specific capacity for solid sodium‐ion batteries of 305 mAh g^?1 and excellent Coulombic efficiency. This work demonstrates that the hybrid network SPEs are promising for SSMB applications.     

Lithium Difluorophosphate‐Based Dual‐Salt Low Concentration Electrolytes for Lithium Metal Batteries

The safety hazards and low Coulombic efficiency originating from the growth of lithium dendrites and decomposition of the electrolyte restrict the practical application of Li metal batteries (LMBs). Inspired by the low cost of low concentration electrolytes (LCEs) in industrial applications, dual‐salt LCEs employing 0.1 m Li difluorophosphate (LiDFP) and 0.4 m LiBOB/LiFSI/LiTFSI are proposed to construct a robust and conductive interphase on a Li metal anode. Compared with the conventional electrolyte using 1 m LiPF₆, the ionic conductivity of LCEs is reduced but the conductivity decrement of the separator immersed in LCEs is moderate, especially for the LiDFP–LiFSI and LiDFP–LiTFSI electrolytes. The accurate Coulombic efficiency (CE) of the Li||Cu cells increases from 83.3% (electrolyte using 1 m LiPF₆) to 97.6%, 94.5%, and 93.6% for LiDFP–LiBOB, LiDFP–LiFSI, and LiDFP–LiTFSI electrolytes, respectively. The capacity retention of Li||LiFePO₄ cells using the LiDFP–LiBOB electrolyte reaches 95.4% along with a CE over 99.8% after 300 cycles at a current density of 2.0 mA cm^?2 and the capacity reaches 103.7 mAh g^?1 at a current density of up to 16.0 mA cm^?2. This work provides a dual‐salt LCE for practical LMBs and presents a new perspective for the design of electrolytes for LMBs.     

Nanocomposite Ionogel Electrolytes for Solid‐State Rechargeable Batteries

Ionogels composed of ionic liquids and gelling solid matrices offer several advantages as solid‐state electrolytes for rechargeable batteries, including safety under diverse operating conditions, favorable electrochemical and thermal properties, and wide processing compatibility. Among gelling solid matrices, nanoscale materials have shown particular promise due to their ability to concurrently enhance ionogel mechanical properties, thermal stability, ionic conductivity, and electrochemical stability. These beneficial attributes suggest that ionogel electrolytes are not only of interest for incumbent lithium‐ion batteries but also for next‐generation rechargeable battery technologies. Herein, recent advances in nanocomposite ionogel electrolytes are discussed to highlight their advantages as solid‐state electrolytes for rechargeable batteries. By exploring a range of different nanoscale gelling solid matrices, relationships between nanoscale material structure and ionogel properties are developed. Furthermore, key research challenges are delineated to help guide and accelerate the incorporation of nanocomposite ionogel electrolytes in high‐performance solid‐state rechargeable batteries.     

Incorporating Solvate and Solid Electrolytes for All‐Solid‐State Li2S Batteries with High Capacity and Long Cycle Life

The development of all‐solid‐state lithium–sulfur batteries is hindered by the poor interfacial properties at solid electrolyte (SE)/electrode interfaces. The interface is modified by employing the highly concentrated solvate electrolyte, (MeCN)₂?LiTFSI:TTE, as an interlayer material at the electrolyte/electrode interfaces. The incorporation of an interlayer significantly improves the cycling performance of solid‐state Li₂S batteries compared to the bare counterpart, exhibiting a specific capacity of 760 mAh g^?1 at cycle 100 (330 mAh g^?1 for the bare cell). Electrochemical impedance spectroscopy shows that the interfacial resistance of the interlayer‐modified cell gradually decreases as a function of cycle number, while the impedance of the bare cell remains almost constant. Cross‐section scanning electron microscopy (SEM)/ energy dispersive X‐ray spectroscopy (EDS) measurements on the interlayer‐modified cell confirm the permeation of solvate into the cathode and the SE with electrochemical cycling, which is related to the decrease in cell impedance. In order to mimic the full permeation of the solvate across the entire cell, the solvate is directly mixed with the SE to form a “solvSEM” electrolyte. The hybrid Li₂S cell using a solvSEM electrolyte exhibits superior cycling performance compared to the solid‐state cells, in terms of Li₂S loading, Li₂S utilization, and cycling stability. The improved performance is due to the favorable ionic contact at the battery interfaces.     

An Air‐Stable and Dendrite‐Free Li Anode for Highly Stable All‐Solid‐State Sulfide‐Based Li Batteries

Li metal is a promising anode material for all‐solid‐state batteries, owing to its high specific capacity and low electrochemical potential. However, direct contact of Li metal with most solid‐state electrolytes induces severe side reactions that can lead to dendrite formation and short circuits. Moreover, Li metal is unstable when exposed to air, leading to stringent processing requirements. Herein, it is reported that the Li₃PS₄/Li interface in all‐solid‐state batteries can be stabilized by an air‐stable Li_xSiS_y protection layer that is formed in situ on the surface of Li metal through a solution‐based method. Highly stable Li cycling for over 2000 h in symmetrical cells and a lifetime of over 100 cycles can be achieved for an all‐solid‐state LiCoO₂/Li₃PS₄/Li cell. Synchrotron‐based high energy X‐ray photoelectron spectroscopy in‐depth analysis demonstrates the distribution of different components within the protection layer. The in situ formation of an electronically insulating Li_xSiS_y protection layer with highly ionic conductivity provides an effective way to prevent Li dendrite formation in high‐energy all‐solid‐state Li metal batteries.     

A 3D Lithium/Carbon Fiber Anode with Sustained Electrolyte Contact for Solid‐State Batteries

To reconcile the energy storage ability and operational safety of lithium metal batteries (LMBs), a transformation from a liquid to a solid‐state system is required. However, Li volume variation, poor interfacial contact, and high operation temperatures hinder its practical applications. To address the above issues, here, an integral structure design for solid‐state LMBs is shown, in which a Li‐preinfused 3D carbon fiber (Li/CF) anode is ionically connected to a cathode via an autopolymerized gel electrolyte. The gel electrolyte helps to encapsulate the liquid electrolyte within the Li/CF anode and the cathode to improve the interfacial contact. The gel also serves as a reservoir that balances the liquid electrolyte supply during repeated Li stripping/plating process. As a result, the symmetrical cells and full cells with Li/CF electrodes exhibit improved cycling stability and effective suppression of dendrites at ambient temperature. This work facilitates the realization of solid‐state LMBs with high energy and high safety.     

On the Functionality of Coatings for Cathode Active Materials in Thiophosphate‐Based All‐Solid‐State Batteries

The last decade has seen considerable advancements in the development of solid electrolytes for solid‐state battery applications, with particular attention being paid to sulfide superionic conductors. Importantly, the intrinsic electrochemical instability of these high‐performance separators highlights the notion that further progress in the field of solid‐state batteries is contingent on the optimization of component material interfaces in order to secure high energy and power densities, while maintaining device safety and a practical cycle life. On the cathode side, the need for a protective coating to inhibit solid electrolyte degradation is clear; however, a mechanistic understanding of the coating functionality remains unresolved, and there is still much room for improvement regarding the methodology and associated material properties. Herein, the essential requirements for a suitable coating are specified and fundamental considerations are discussed in detail. Additionally, this article will provide an overview of the various material classes, assessment protocols and practical coating methods, as well as an outlook on the development of coatings for cathode active materials in thiophosphate‐based solid‐state batteries.     

Design Strategies,Practical Considerations,and New Solution Processes of Sulfide Solid Electrolytes for All‐Solid‐State Batteries

Owing to the ever‐increasing safety concerns about conventional lithium‐ion batteries, whose applications have expanded to include electric vehicles and grid‐scale energy storage, batteries with solidified electrolytes that utilize nonflammable inorganic materials are attracting considerable attention. In particular, owing to their superionic conductivities (as high as ≈10^?2 S cm^?1) and deformability, sulfide materials as the solid electrolytes (SEs) are considered the enabling material for high‐energy bulk‐type all‐solid‐state batteries. Herein the authors provide a brief review on recent progress in sulfide Li‐ and Na‐ion SEs for all‐solid‐state batteries. After the basic principles in designing SEs are considered, the experimental exploration of multicomponent systems and ab initio calculations that accelerate the search for stronger candidates are discussed. Next, other issues and challenges that are critical for practical applications, such as instability in air, electrochemical stability, and compatibility with active materials, are discussed. Then, an emerging progress in liquid‐phase synthesis and solution process of SEs and its relevant prospects in ensuring intimate ionic contacts and fabricating sheet‐type electrodes is highlighted. Finally, an outlook on the future research directions for all‐solid‐state batteries employing sulfide superionic conductors is provided.     

Biomaterials for High‐Energy Lithium‐Based Batteries: Strategies,Challenges, and Perspectives

Developing high‐performance batteries through applying renewable resources is of great significance for meeting ever‐growing energy demands and sustainability requirements. Biomaterials have overwhelming advantages in material abundance, environmental benignity, low cost, and more importantly, multifunctionalities from structural and compositional diversity. Therefore, significant and fruitful research on exploiting various natural biomaterials (e.g., soy protein, chitosan, cellulose, fungus, etc.) for boosting high‐energy lithium‐based batteries by means of making or modifying critical battery components (e.g., electrode, electrolyte, and separator) are reported. In this review, the recent advances and main strategies for adopting biomaterials in electrode, electrolyte, and separator engineering for high‐energy lithium‐based batteries are comprehensively summarized. The contributions of biomaterials to stabilizing electrodes, capturing electrochemical intermediates, and protecting lithium metal anodes/enhancing battery safety are specifically emphasized. Furthermore, advantages and challenges of various strategies for fabricating battery materials via biomaterials are described. Finally, future perspectives and possible solutions for further development of biomaterials for high‐energy lithium‐based batteries are proposed.     

A Lithium Amide‐Borohydride Solid‐State Electrolyte with Lithium‐Ion Conductivities Comparable to Liquid Electrolytes

High ionic conductivity of up to 6.4 × 10^?3 S cm^?1 near room temperature (40 °C) in lithium amide‐borohydrides is reported, comparable to values of liquid organic electrolytes commonly employed in lithium‐ion batteries. Density functional theory is applied coupled with X‐ray diffraction, calorimetry, and nuclear magnetic resonance experiments to shed light on the conduction mechanism. A Li₄Ti₅O₁₂ half‐cell battery incorporating the lithium amide‐borohydride electrolyte exhibits good rate performance up to 3.5 mA cm^?2 (5 C) and stable cycling over 400 cycles at 1 C at 40 °C, indicating high bulk and interfacial stability. The results demonstrate the potential of lithium amide‐borohydrides as solid‐state electrolytes for high‐power lithium‐ion batteries.     

A High‐Throughput Search for Functionally Stable Interfaces in Sulfide Solid‐State Lithium Ion Conductors

Interfacial reactions between ceramic‐sulfide solid‐electrolytes and common electrodes have remained a major impediment to the development of solid‐state lithium‐ion batteries. In practice, this means that ceramic‐sulfide batteries require a suitable coating material to isolate the electrolyte from the electrode materials. In this work, the interfacial stability of Li₁₀SiP₂S₁₂ with over 67 000 materials is computationally evaluated. Over 2000 materials that are predicted to form stable interfaces in the cathode voltage range and over 1000 materials for the anode range are reported on and cataloged. LiCoO₂ is chosen as an example cathode material to identify coating compounds that are stable with both Li₁₀SiP₂S₁₂ and a common cathode. The correlation between elemental composition and multiple instability metrics (e.g., chemical/electrochemical) is analyzed, revealing key trends in, amongst others, the role of anion selection. A new binary‐search algorithm is introduced for evaluating the pseudo‐phase with improved speed and accuracy. Computational challenges posed by high‐throughput interfacial phase‐diagram calculations are highlighted as well as pragmatic computational methods to make such calculations routinely feasible. In addition to the over 3000 materials cataloged, representative materials from the anionic classes of oxides, fluorides, and sulfides are chosen to experimentally demonstrate chemical stability when in contact with Li₁₀SiP₂S₁₂.     

Interfacial Incompatibility and Internal Stresses in All‐Solid‐State Lithium Ion Batteries

Rechargeable Li‐ion batteries (LIBs) are electrochemical storage device widely applied in electric vehicles, mobile electronic devices, etc. However, traditional LIBs containing liquid electrolytes suffer from flammability, poor electrochemical stability, and limited operational temperature range. Replacement of the liquid electrolytes with inorganic solid‐state electrolytes (SSEs) would solve this problem. However, several critical issues, such as poor interfacial compatibility, low ionic conductivity at ambient temperatures, etc., need to be surmounted before the commercialization of all‐solid‐state Li‐ion batteries (ASSLIBs). In this review, a brief historical context for the inorganic SSEs is described first. Then, two critical issues in the ASSLIBs are highlighted: interfacial incompatibility of the electrodes and SSEs and internal stresses. For the interfacial incompatibility, the discussion is focused on the dynamic characterization of the electrode/SSE interfaces, the origin and evolution of the interfacial resistance, and interface engineering to minimize the interfacial resistance. The internal stresses in the ASSLIBs are another major concern because rigid contacts are introduced. Stress generation, stress evolution during battery cycling, stress measurement/simulation, and ways to alleviate the stresses are outlined in detail. Finally, current challenges and perspectives for future development of the inorganic SSEs and ASSLIBs are outlined.     

Perovskite Membranes with Vertically Aligned Microchannels for All‐Solid‐State Lithium Batteries

Perovskite‐type solid‐state electrolytes exhibit great potential for the development of all‐solid‐state lithium batteries due to their high Li‐ion conductivity (approaching 10^?3 S cm^?1), wide potential window, and excellent thermal/chemical stability. However, the large solid–solid interfacial resistance between perovskite electrolytes and electrode materials is still a great challenge that hinders the development of high‐performance all‐solid‐state lithium batteries. In this work, a perovskite‐type Li_0.34La_0.51TiO₃ (LLTO) membrane with vertically aligned microchannels is constructed by a phase‐inversion method. The 3D vertically aligned microchannel framework membrane enables more effective Li‐ion transport between the cathode and solid‐state electrolyte than a planar LLTO membrane. A significant decrease in the perovskite/cathode interfacial resistance, from 853 to 133 Ω cm², is observed. It is also demonstrated that full cells utilizing LLTO with vertically aligned microchannels as the electrolyte exhibit a high specific capacity and improved rate performance.