Investigating Plastic Deformation Between Silicon and Solid Electrolyte in All-Solid-State Batteries Using Operando X-ray Tomography

Si anodes in all-solid-state batteries are expected to achieve high energy density and durability because large volume changes in Si can be mechanically suppressed by the hardness of solid electrolytes. However, the effects of volume changes on the mechanical interface between Si and solid electrolytes during charge/discharge reactions have not been investigated. In this study, operando X-ray computed tomography was used to determine the microstructure of an all-solid-state battery comprising Si active materials and a solid sulfide electrolyte, Li10GeP2S12, during charge/discharge reactions. To evaluate the volume expansion/contraction effects on the charge/discharge properties, the tortuosity of the ion conduction path and the contact area fraction between Si and the solid electrolyte during the charge/discharge reactions were quantitatively estimated. Shell-shaped voids around the Si particles were observed after Si shrinkage owing to the plastic deformation of the solid electrolyte. This characteristic resulted in poor charge/discharge efficiency and incomplete delithiation in the battery. These results will facilitate the design optimization of Si composite electrodes, which will be highly beneficial to the development of effective all-solid-state batteries.