Composite polymer electrolytes based on poly(ether-ester) and Li1.3Al0.3Ti1.7(PO4)3 enabling high-performance all-solid-state flexible lithium metal batteries

The quest for next-generation energy storage systems has led to the development of high-voltage all-solid-state lithium metal batteries (ASSLMBs), which promise unprecedented energy density and safety. However, the challenge lies in creating of a robust electrolyte that can meet high room temperature ionic conductivity, Li-ion transference number and a wide electrochemical stability window (ESW) while maintaining flexibility and compatibility with lithium metal anodes. Here, novel polyurethane-based composite polymer electrolytes (CPEs) have been successfully fabricated by the cross-linking reaction of poly(1,5-dioxepan-2-one) diols (poly(ether-ester) soft segment) and hexamethylene diisocyanate trimer (hard segment) (PDH) blending with inorganic NASICON-type ceramic fillers Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (PDH@LATP). The resulting CPE exhibits an impressive ionic conductivity of 1.65 × 10 −4  S cm −1  at room temperature and a Li-ion transference number of 0.63, which is attributed to the amorphous structure of PDH and the formation of an interconnected ionic pathway by the inorganic filler. The incorporation of LATP also improve the ESW of CPE to 5.3 V while maintaining good mechanical properties. Therefore, the assembled LiFePO 4 /PDH@LATP/Li batteries displayed low interfacial resistance, Li dendrite suppression, high specific capacity and excellent cyclic performance. The high-voltage LiNi 0.5 Co 0.2 Mn 0.3 O 2 /PDH@LATP/Li batteries also exhibits good cycling performance and durability. The design principles and materials presented herein provide a blueprint for the next wave of ASSLMBs.