Aqueous-Solution Process for Li4SnS4 Solid Electrolytes for All-Solid-State Lithium-Ion Batteries

Safety issues of conventional lithium-ion batteries (LIBs) employing flammable liquid electrolytes prohibit its large-scale application such as electric vehicles and energy storage systems. In this regard bulk-type all-solid-state lithium-ion batteries (ASLBs) using nonflammable inorganic solid electrolytes (SEs) are considered as a candidate for next-generation battery systems. Particularly, the sulfide SEs are promising candidate because of its higher ionic conductivities compare to liquid electrolytes.[1] However, the performances of ASLBs are critically limited by poor ionic contacts between active materials and SE in the electrodes.[2] Herein, we report aqueous solutions of Li4SnS4 which could be further solidified on the surface of active materials (LiCoO2). SE coating layers that provide favorable ionic pathways result in significantly improved electrochemical performance of ASLBs. Side reaction by the exposure of LiCoO2 to aqueous solutions is minimized by using pre-dissolved Li4SnS4 solution