Solid electrolytes with good chemical/mechanical stability and high ionic conductivity have been considered to be the best choice for highenergy Li metal batteries. However, dendrite growth and the poor contact between lithium and the solid electrolyte seriously hinder the development of these batteries, especially when facing infinite volume fluctuations during the cycle process. Herein, a rigid flexible self-adaptive structure electrolyte (SASE) has been designed to suppress lithium dendrite growth and guarantee an intimate contact between lithium and the electrolyte. Benefiting from the internal elastomer and outer shell with high Young's modulus cooperating with each other, the battery shows excellent electrochemical performance. The symmetric cell with the SASE electrolyte can cycle stably for more than 700 h, and the full cell with this electrolyte also exhibits excellent rate performance. This work provides a new strategy to design dendrite-free and high-energy solid Li metal batteries and a strong support for its application in future.