Functional polyethylene glycol-based solid electrolytes with enhanced interfacial compatibility for room-temperature lithium metal batteries

The interface issues of electrodes/solid-state electrolytes have been limiting the application of room-temperature lithium metal batteries. In situ polymerization technology achieved the realization of solid-solid ultra-conformal interface contacts. However, few efforts have been directed toward the precursor compatibility of electrodes and simultaneous chemical/electrochemical performances, which may directly cause high interface impedance, severe lithium dendrites and unsatisfactory stability of assembled cells. In this work, high-performance polyethylene glycol-based solid electrolytes with enhanced interfacial compatibility was prepared by an in situ copolymerization of functional polyethylene glycol and vinylene carbonate, in which vinylene carbonate tends to preferentially produce poly(vinylene carbonate) via anionic polymerization within solid electrolyte interface layers on the lithium metal surface to stabilize Li metal, and copolymerization with polyethylene glycol improves overall electrochemical performances. The SPE-assembled Li-Li symmetrical batteries stably run for over 2000 h; meanwhile, SPEs exhibit a high room-temperature ionic conductivity (0.4 mS cm −1 ), high lithium ion transference number (0.46) and wide electrochemical stability window (5.1 V). Resultant LiFePO 4 /Li metal batteries show a considerable rate capability (up to 5C) and a super-long cycling performance (>300 cycles) at 1C at room temperature. In addition, assembled cells with high-loading cathodes (5.5-10.5 mg cm −2 ) deliver high initial capacities and good capacity retentions. The simple and scalable approach may enable the industrialization and application of room-temperature lithium metal batteries. A high-performance solid polymer electrolyte with enhanced interfacial compatibility was synthesized via an in situ polymerization of functional polyethylene glycol combined with the in situ formation of stable SEI layers by vinylene carbonate.