Robust solid-state interface with a deformable glass interlayer in sulfide-based all-solid-state batteries

We introduced a new elastic interface layer (EIL), (Li2S)(0.75)(P2S5)(0.25) glass, in all-solid-state batteries (ASSBs) to improve the solid-state interfacial structure, and analyzed its structural evolution in electrochemical charge/discharge cycles. This EIL had a lower bulk modulus, thereby providing good powder processability and high mechanical deformability against volume changes of the electrode. Compared to a cell configuring EIL, the reference cell exhibited a considerable increase in the electrolyte resistance; moreover, a new resistance component was identified in the high-frequency region (500-50 kHz). This high-resistance component resulting from interfacial deterioration such as metal fragmentation and micropore formation was successfully suppressed by applying a mechanically deformable EIL. We believe that this study would provide insights into the application of EIL for configuring a stable interface with a metallic electrode in ASSBs.