Acylamino-functionalized crosslinker to synthesize all-solid-state polymer electrolytes for high-stability lithium batteries

All-solid-state polymer electrolytes (SPEs) are key for improving lithium-ion battery (LIB) safety and the practical application of metallic Li anodes. The major challenges of developing SPEs are their ionic conductivity, interfacial affinity, and flammability. In this article, synthesis of an SPE comprising lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and poly(ethylene oxide) networked with an acylamino-functionalized crosslinker is reported. The acylamino sites, urethane and biuret linkages, dissociate LiTFSI and may form deep-eutectic-solvent domains to facilitate ion transport. This SPE is fire-retarding because CO₂ evolves when the urethane decomposes at high temperatures. When operated at room temperature, the all-solid-state Li|SPE|LiFePO₄ cell exhibits a high rate capability and long lifespan. Due to the high elasticity of the SPE, the polymers can self-rearrange during operation to reduce the Li–SPE interfacial resistance and regulate Li⁺-ion transport for uniform Li deposition. The rearrangement may involve migration of the low-energy alkane chains in the crosslinker toward the Li-anode, resulting in overspreading of lithiophilic carbonyl groups and F-atoms of TFSI⁻ at the interface. This rearrangement property enables the SPE to act as an artificial interlayer in liquid-electrolyte LIBs. The advantages of using an acylamino-functionalized crosslinker to synthesize a networked SPE for high ionic conductivity and interfacial compatibility are demonstrated.