Ultrahigh Elastic Polymer Electrolytes for Solid-State Lithium Batteries with Robust Interfaces

Solid polymer electrolytes (SPEs) are promising for solid-state lithium batteries, but their practical application is significantly impeded by their low ionic conductivity and poor compatibility. Here, we report an ultrahigh elastic SPE based on cross-linked polyurethane (PU), succinonitrile (SN), and lithium bistrifluoromethanesulfonimide (LiTFSI). The resulting electrolyte (PU-SN-LiTFSI) exhibits an ionic conductivity of 2.86 × 10^-4 S cm^-1, a tensile strength of 3.8 MPa, and a breaking elongation exceeding 3000% at room temperature. A solid-state lithium battery using the electrolyte exhibits a high specific capacity of 150 mAh g^-1 at 0.2C and a long cycling life of up to 700 cycles at 0.5C at room temperature, showing one of the best performances among its counterparts. The excellent performances are attributed to the fact that its ultrahigh elasticity, good ionic conductivity, tensile strength, and electrochemical stability contribute to robust electrode/electrolyte interfaces, thus greatly decreasing the charge-transfer resistance in charge/discharge processes. Our investigations provide a novel strategy to address the intrinsic interfacial issue of solid-state batteries.