Solvated Ionic‐Liquid Incorporated Soft Flexible Cross‐Linked Network Polymer Electrolytes for Safer Lithium Ion Secondary Batteries

Abstract The present work demonstrates the solvent‐free, highly flexible, self‐supporting crosslinked network polymer electrolyte membranes with decent ion conductivities and stable battery performance (in terms of rate capability and cycle stability) at ambient temperatures. The network polymer electrolyte membranes are prepared by “thiol‐epoxy” and “thiol‐ene” (co)polymerization using pentaerythritol tetrakis(3‐mercaptopropionate) (PEMP) and terminal‐functionalized poly(ethylene glycol) (PEG). The network polymer electrolyte membranes contain small amounts of solvated ionic liquids (equimolar mixture of tetraglyme and lithium salt) at different lithium salt molar concentrations. The obtained membranes display remarkable homogeneity and high amorphous characteristics, good mechanical robustness, high thermal stability, wide electrochemical stability (>4.20 V vs Li/Li + ), and superior lithium ion transference number ( t Li+ = 0.20–0.50). The electrochemical and spectroscopic study of the network polymer electrolyte membranes reveals the influence of solvated ionic liquid on the ion conduction, mechanical, thermal, and electrochemical properties. The overall performance of the present crosslinked polymer network electrolyte containing solvated ionic liquid systems postulates the possibility of their practical implementation in the construction of safe and durable alternative electrolytes for high‐performance lithium ion batteries working at wide temperatures.