Solid-state lithium metal batteries (LMBs) are recognized as the future of energy storage technology, offering unparalleled energy densities and safety that far exceed those of current lithium-ion batteries . However, the widespread adoption of solid-state LMBs in sectors such as electric vehicles, electric aviation and energy storage is hindered by significant challenges, particularly in the development of electrolyte materials. Among different types of solid electrolytes, solid polymer electrolytes (SPEs) stand out as promising candidates due to their inherent safety and processibility advantages as well as the potential to facilitate high energy LMBs. Unfortunately, the majority of SPEs require plasticization with a liquid solvent to improve their intrinsically low ionic conductivity and poor wettability, which not only compromises the mechanical properties but also introduces safety concerns similar to those of liquid electrolytes such as leakage and flammability. Consequently, designing all-solid-state SPE systems that maintain both high ionic conductivity and mechanical integrity remains a significant challenge.