Coatable Li₄SnS₄ Solid Electrolytes Prepared from Aqueous Solutions for All-Solid-State Lithium-Ion Batteries

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.