Decoupled Regulation and Synergetic Optimization of Mechanical and Electrochemical Performances of Stretchable Solid Polymer Electrolytes

Solid polymer electrolytes (SPEs) are regarded as ideal electrolytes for flexible lithium batteries due to their intrinsic safety and interfacial compatibility, but their practical application is limited by the intrinsic antagonism between mechanical properties and ionic conductivity. Herein, a novel electrolyte (ISSPE) with a stretchable SEBS (styrene–ethylene–butylene–styrene) framework and a highly percolating Li+-conductive network has been in situ integrated. The presented structural design decoupled the mechanical properties and electrochemical performance, where the elastic phase and the ion-conducting phase each play their own role, achieving excellent elongation at break of 601% at room temperature, tensile strength of 5.01 MPa, high ionic conductivity of 0.77 mS cm–1 and an excellent Li+ transference number (0.76), while an electrochemical stability window of 5.45 V vs Li+/Li was achieved. Owing to the conformal electrode/electrolyte interface achieved by the in situ polymerization process, ISSPE shows excellent performance in Li||LiFePO4 and Li||LiCoO2 cells, with significant inhibition of dendrite growth at the surface of the lithium metal anode after cycling. This study shows new light on the design of SPEs that are both Li+ conductive and mechanical tolerance.