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. •All-solid-state battery with (Li2S)0.75(P2S5)0.25 interlayer (GLcell) was prepared.•GLcell showed a better electrochemical performance than the reference cell.•GLcell suppressed interfacial deterioration caused by fragmentation of components.•Excellence of GLcell originated from high deformability with low bulk modulus.