Mechanical influence mechanisms of silicon anodes in solid-state batteries under low stack pressure

Microparticulate silicon (Si) has been successfully used in solid lithium-ion battery anodes due to its strength in high gravimetric/volumetric capacity and low risk of dendrite growth. Nevertheless, the operation condition of low stack pressure challenges the cycle life of the assembled microparticulate Si-based solid-state batteries. In this work, we unveiled that solely low volume expansion of the Si anode is insufficient to achieve good cyclic stability for solid-state batteries under low stack pressure, and the intimate Si anode-solid electrolyte interfacial contact must be considered, which is found to be influenced by the mechanical deformation of Si. As a result, for the batteries with organic/inorganic composite solid-state electrolytes, the low-expansion microparticulate silicon oxide (SiO x ) anode is employed and achieves stable cycling performance and high areal capacity (23 mAh cm −2 ) with good interfacial compatibility under 0 MPa stack pressure. For all-solid-state batteries using sulfide solid-state electrolyte, the hybrid of microparticulate SiO x and Si combined with the low expansion of SiO x and good plastic deformation ability of Si is applied and affords superior cyclic stability under decreased stack pressure. This work refreshes the understanding of the anode design principle for low-stack-pressure solid-state batteries using organic/inorganic composite solid-state electrolytes or sulfide solid-state electrolytes. • The SiO x anode achieves high areal capacity with organic/inorganic SSE. • The μSi anode exhibits superior interface stability with sulfide SSE. • The hybrid SiO x and μSi anode combines low expansion and plastic deformation.