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Developing high‐performance all‐solid‐state batteries is contingent on finding solid electrolyte materials with high ionic conductivity and ductility. Here we report new halide‐rich solid solution phases in the argyrodite Li6PS5Cl family, Li6−xPS5−xCl1+x, and combine electrochemical impedance spectroscopy, neutron diffraction, and 7Li NMR MAS and PFG spectroscopy to show that increasing the Cl−/S2− ratio has a systematic, and remarkable impact on Li‐ion diffusivity in the lattice. The phase at the limit of the solid solution regime, Li5.5PS4.5Cl1.5, exhibits a cold‐pressed conductivity of 9.4±0.1 mS cm−1 at 298 K (and 12.0±0.2 mS cm−1 on sintering)—almost four‐fold greater than Li6PS5Cl under identical processing conditions and comparable to metastable superionic Li7P3S11. Weakened interactions between the mobile Li‐ions and surrounding framework anions incurred by substitution of divalent S2− for monovalent Cl− play a major role in enhancing Li+‐ion diffusivity, along with increased site disorder and a higher lithium vacancy population. [ABSTRACT FROM AUTHOR]

Abstract: 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. [ABSTRACT FROM AUTHOR]

All-solid-state sodium-ion batteries that operate at room temperature are attractive candidates for use in large-scale energy storage systems. However, materials innovation in solid electrolytes is imperative to fulfill multiple requirements, including high conductivity, functional synthesis protocols for achieving intimate ionic contact with active materials, and air stability. A new, highly conductive (1.1 mS cm−1 at 25 °C, Ea=0.20 eV) and dry air stable sodium superionic conductor, tetragonal Na3SbS4, is described. Importantly, Na3SbS4 can be prepared by scalable solution processes using methanol or water, and it exhibits high conductivities of 0.1-0.3 mS cm−1. The solution-processed, highly conductive solidified Na3SbS4 electrolyte coated on an active material (NaCrO2) demonstrates dramatically improved electrochemical performance in all-solid-state batteries. [ABSTRACT FROM AUTHOR]

Development of new sulfide Li+ superionic conductors with mechanical sinterability is the key to the success of all-solid-state lithium batteries. While phosphorus-containing sulfide superionic conductor materials have been widely investigated, phosphorus-free materials showing good air-stability have been overlooked. Herein, the Li+ dynamics in Sb-substituted Li 4 SnS 4 showing a high Li+ conductivity of max. 0.85 mS cm−1 at 30 °C and excellent dry-air stability as well as negligible H 2 S evolution is described. Structural analysis with X-ray and neutron diffraction reveals that Sb-substitution renders an expansion of the lattice volume and formation of Li vacancies. Additionally, 1D-preferable 3D Li+ diffusion channels in Li 4-x Sn 1-x Sb x S 4 are disclosed. The fast Li+ diffusion in Li 4-x Sn 1-x Sb x S 4 is rationalized by complementary analysis using AC impedance measurements, bond valence energy landscape calculation, and 7Li nuclear magnetic resonance spectroscopy. Excellent electrochemical performances of TiS 2 electrodes employing Li 3.85 Sn 0.85 Sb 0.15 S 4 in all-solid-state batteries are demonstrated. Image 1 • Sb-substituted Li 4 SnS 4 shows a maximum Li+ conductivity of 0.85 mS cm−1 at 30 °C. • Excellent dry-air stability and negligible H 2 S evolution are confirmed. • 1D-preferable 3D Li+ diffusion channels disclosed by neutron diffraction analysis. • Performance of all-solid-state Li-ion batteries using Li 3.85 Sn 0.85 Sb 0.15 S 4. [ABSTRACT FROM AUTHOR]

For mass production of all‐solid‐state lithium‐ion batteries (ASLBs) employing highly Li+ conductive and mechanically sinterable sulfide solid electrolytes (SEs), the wet‐slurry process is imperative. Unfortunately, the poor chemical stability of sulfide SEs severely restrict available candidates for solvents and in turn polymeric binders. Moreover, the binders interrupt Li+‐ionic contacts at interfaces, resulting in the below par electrochemical performance. In this work, a new scalable slurry fabrication protocol for sheet‐type ASLB electrodes made of Li+‐conductive polymeric binders is reported. The use of intermediate‐polarity solvent (e.g., dibromomethane) for the slurry allows for accommodating Li6PS5Cl and solvate‐ionic‐liquid‐based polymeric binders (NBR‐Li(G3)TFSI, NBR: nitrile−butadiene rubber, G3: triethylene glycol dimethyl ether, LiTFSI: lithium bis(trifluoromethanesulfonyl)imide) together without suffering from undesirable side reactions or phase separation. The LiNi0.6Co0.2Mn0.2O2 and Li4Ti5O12 electrodes employing NBR‐Li(G3)TFSI show high capacities of 174 and 160 mA h g−1 at 30 °C, respectively, which are far superior to those using conventional NBR (144 and 76 mA h g−1). Moreover, high areal capacity of 7.4 mA h cm−2 is highlighted for the LiNi0.7Co0.15Mn0.15O2 electrodes with ultrahigh mass loading of 45 mg cm−2. The facilitated Li+‐ionic contacts at interfaces paved by NBR‐Li(G3)TFSI are evidenced by the complementary analysis from electrochemical and 7Li nuclear magnetic resonance measurements. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electrochemo-mechanical effects for all-solid-state batteries are categorized. • The mechanical properties of solid electrolytes are considered. • Stress sources, resulting cell failures, and stress cross-talks are discussed. All-solid-state batteries (ASSBs) using inorganic solid electrolytes (SEs) are in the spotlight for next-generation energy storage devices because of their potential for outstanding safety and high energy density. Recent progress in this field has been primarily based on advances in materials, such as the discovery of SEs with high ionic conductivities and the improvement of interfacial stability in electrodes. However, the use of inelastic SEs causes severe electrochemo-mechanical failures, such as cathode active material (CAM) disintegration, CAM/SE contact loss, and stress build-up during cycling, deteriorating the Li+ and e− transport pathways. Although these concerns have been addressed previously, they have not been contextualized systematically in terms of the mechanical interactions among the components and their impacts on electrochemical performance. Here, we categorize the electrochemo-mechanical effect in ASSBs and its ramifications in terms of stress sources, active materials, composite electrodes, and cell stacks. [ABSTRACT FROM AUTHOR]