As All-Solid-State Batteries (ASSBs) include only solid-solid interfaces as reaction sites, the contact at the interfaces easily deteriorates due to the volumetric change of active materials during charge and discharge. Formation and maintenance of sufficient contacts at the interfaces are essential for the good performance of ASSBs. In this study, those contact problems were addressed by improving the plastic deformation of Li_10.35Ge_1.35P_1.65S₁₂ solid electrolyte after pulverization. Due to their suitable mechanical properties for ASSBs, size-controlled LGPS better accommodate volume changes experienced by the anode metal and cathode material during battery evaluation, providing improved performances.