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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]

Bulk-type all-solid-state lithium-ion batteries (ASLBs) for large-scale energy-storage applications have emerged as a promising alternative to conventional lithium-ion batteries (LIBs) owing to their superior safety. However, the electrochemical performance of bulk-type ASLBs is critically limited by the low ionic conductivity of solid electrolytes (SEs) and poor ionic contact between the active materials and SEs. Herein, highly conductive (0.14 mS cm−1) and dry-air-stable SEs (Li4SnS4) are reported, which are prepared using a scalable aqueous-solution process. An active material (LiCoO2) coated by solidified Li4SnS4 from aqueous solutions results in a significant improvement in the electrochemical performance of ASLBs. Side-effects of the exposure of LiCoO2 to aqueous solutions are minimized by using predissolved Li4SnS4 solution. [ABSTRACT FROM AUTHOR]

The excellent stability of sulfide solid electrolytes with solvate ionic liquids Li(triethylene glycol dimethyl ether)bis(trifluoromethanesulfonyl)imide (Li(G3)TFSI), and their application for high‐performance, all‐solid‐state lithium‐ion batteries are successfully demonstrated. The addition of a small amount of Li(G3)TFSI gives an alternative ionic pathway through normally poor solid–solid contacts, leading to a dramatic increase in LiFePO4 composite electrode capacity. [ABSTRACT FROM AUTHOR]

As lithium rechargeable batteries are considered a potential candidate for large-scale energy storage applications in devices such as electric vehicles (EVs) and smart grids, their safety has become of prime concern. This calls for the need to replace the flammable organic liquid electrolyte (LE) with an inorganic solid electrolyte (SE), and thus, develop bulk-type all-solid-state lithium batteries (ASLBs), fabricated using a scalable process. Sulfide SEs are considered the most competitive candidate owing to their high conductivity at room temperature (10−3-10−2 S cm−1), which is comparable to that of LEs, and their ductility, which enables the fabrication of ASLBs simply using cold pressing. In the present review, issues and challenges to be faced for the fabrication of bulk-type ASLBs using sulfide SEs are presented and discussed, with a special focus on the development of SEs, compatibility of the electrode materials with SEs, and structure of the composite electrodes. Recent progress made with the aim of addressing the aforementioned issues and challenges is also presented, to provide an outlook on the future of SEs and ASLBs. [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]

Bulk-type all-solid-state lithium-ion batteries (ASLBs) have the potential to be superior to conventional lithium-ion batteries (LIBs) in terms of safety and energy density. Sulfide SE materials are key to the development of bulk-type ASLBs because of their high ionic conductivity (max of 10-2 S cm-1) and deformability. However, the severe reactivity of sulfide materials toward common polar solvents and the particulate nature of these electrolytes pose serious complications for the wet-slurry process used to fabricate ASLB electrodes, such as the availability of solvent and polymeric binders and the formation of ionic contacts and networks. In this work, we report a new scalable fabrication protocol for ASLB electrodes using conventional composite LIB electrodes and homogeneous SE solutions (Li6PS5Cl (LPSCl) in ethanol or 0.4LiI-0.6Li4SnS4 in methanol). The liquefied LPSCl is infiltrated into the tortuous porous structures of LIB electrodes and solidified, providing intimate ionic contacts and favorable ionic percolation. The LPSCl-infiltrated LiCoO2 and graphite electrodes show high reversible capacities (141 and 364 mA h g-1) at 0.14 mA cm-2 (0.1 C) and 30 °C, which are not only superior to those for conventional dry-mixed and slurry-mixed ASLB electrodes but also comparable to those for liquid electrolyte cells. Good electrochemical performance of ASLBs employing the LPSCl-infiltrated LiCoO2 and graphite electrodes at 100 °C is also presented, highlighting the excellent thermal stability and safety of ASLBs. [ABSTRACT FROM AUTHOR]