Intramolecular Design of Poly(ethylene oxide) for Solid-State Electrolytes and Next-Generation High-Energy Batteries

Solid-state electrolytes (SSEs) are key materials for next-generation high-energy batteries because of their enhanced chemical and mechanical stabilities. Poly(ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) exhibit great physical contact with electrodes, electrochemical compatibility with lithium (Li) metal anodes, as well as easy processibility and high economic efficiency, having become the pioneer and one frontrunner for developing all-solid-state high-energy batteries. However, PEO-based SPEs also suffer from a trade-off between ionic conductivity and mechanical strength, an insufficient cationic transference number, and a weak high-voltage stability, limiting their practical achievement in desirable power and energy density. Herein, we present a comprehensive overview on the intramolecular design strategies of PEO, which has the potential to fundamentally tackle above challenges compared to the intermolecular plasticizer or ceramic blending approaches. Topological and chemical designs for target mechano-electro-chemical performance are classified and summarized in detail. On this basis, a perspective on the unconquered issues and future directions is proposed, providing guidance for the design and application of high-performance SSEs for next-generation high-energy batteries, with special emphasis on the rational integration of intramolecular and intermolecular methods and the development of advanced manufacture techniques for flexible yet robust thin films.