The research progress in polyethylene oxide polymer electrolytes

Abstract All‐solid‐state lithium batteries (ASSLBs) are the leading next‐generation energy storage solutions due to their superior safety, high energy density, and broad temperature adaptability. Solid‐state polymer electrolytes (SPEs) are critical factors in the development of ASSLBs, requiring high ionic conductivity (IC), mechanical strength, and electrode interface stability. Polyethylene oxide (PEO) is a significant SPE material, offering lithium salt complexation and flexible processability. Its high crystallinity causes poor IC at room temperature and uncontrollable lithium dendrite growth, which are hindering ASSLB commercialization. In this review, we mainly summarize three optimization synthesis strategies for PEO‐based SPEs: (1) Optimizing PEO molecular design: Reducing the crystallinity of PEO through the molecular structure design of linear, cross‐linked, and hyperbranched copolymers elevates the room‐temperature IC of the electrolyte to 10 −5 –10 −4 S·cm −1 . (2) Doping or modification: Introducing inert, active, and functional fillers for the doping modification of PEO‐based electrolytes effectively promotes lithium salt dissociation and suppresses lithium dendrite growth. Inert fillers can enhance the room‐temperature IC of the electrolyte by 50‐fold. (3) Advanced material preparation methods: Employing advanced fabrication techniques such as solution casting, electrospinning, 3D printing, and doctor blading optimizes the microstructure of PEO‐based electrolytes to enhance overall performance. For instance, electrolytes prepared by automated doctor‐blading exhibit a conductivity of 2.19 × 10 −4 S·cm −1 at 17°C. Although these strategies improve cyclic stability and safety, their performance at room temperature remains below commercial standards. Therefore, future research should focus on multiscale characterization techniques to delve into the electrode/electrolyte interface mechanisms for fabricating high‐energy‐density, long‐life ASSLBs.