Allylamine-functionalized comb-like polymers for balancing ion transport and mechanical stiffness in solid polymer electrolytes

Solid-state polymer electrolytes (SPEs) have emerged as promising candidates for next-generation solid state lithium metal batteries (SSLMBs) due to their improved safety, enhanced interfacial stability, and potential to suppress dendrite growth compared with conventional liquid electrolytes. However, simultaneously achieving high ionic conductivity and adequate mechanical robustness remains a critical bottleneck hindering the widespread implementation of SPE-based SSLMBs. In this work, we report the synthesis of a comb-like copolymer based on polyetheramine and allylamine blocks grafted onto a poly(ethylene- alt -maleic anhydride) backbone, designed to form a self-standing and mechanically robust SPE membrane. The allylamine units introduce reactive sites for post-polymerization crosslinking, providing membrane integrity and structural strength, whereas Li + transport is facilitated by the ethylene oxide units of the polyetheramine. The resulting SPE delivers decent ionic conductivities of 1.4 × 10 −4 S cm −1 at 45 °C, without the use of any plasticizer. In particular, the allylamine-functionalized SPE demonstrates excellent compatibility with lithium metal (LiM), sustaining stable galvanostatic cycling for more than 4000 h in lithium symmetric cells and more than 150 cycles with 80% capacity retention in LiFePO 4 ||LiM cells at 45 °C. Overall, this work offers a promising polymer design strategy for developing high-performance SPE-based SSLMBs and reducing their operational temperatures.