Rational Design of F-Modified Polyester Electrolytes for Sustainable All-Solid-State Lithium Metal Batteries.

Solid polymer electrolytes (SPEs) are one of the most practical candidates for solid-state batteries owing to their high flexibility and low production cost, but their application is limited by low Li conductivity and a narrow electrochemical window. To improve performance, it is necessary to reveal the structure-property relationship of SPEs. Here, 23 fluorinated linear polyesters were prepared by editing the coordination units, flexible linkage segments, and interface passivating groups. Besides the traditionally demonstrated coordinating capability and flexibility of polymer chains, the molecular asymmetry and resulting interchain aggregation are observed critical for Li conductivity. By tailoring the molecular asymmetry and coordination ability of polyesters, the Li conductivity can be raised by 10 times. Among these polyesters, solvent-free poly(pentanediol adipate) delivers the highest room-temperature Li conductivity of 0.59 × 10 S cm. The chelating coordination of oxalate and Li leads to an electron delocalization of alkoxy oxygen, enhancing the antioxidation capability of SPEs. To lower the cost, high-value LiTFSI in SPEs is recycled at 90%, and polyesters can be regenerated at 86%. This work elucidates the structure-property relationship of polyester-based SPEs, displays the design principles of SPEs, and provides a way for the development of sustainable solid-state batteries.