In-situ polymerized PEO-based solid electrolytes contribute better Li metal batteries: Challenges, strategies, and perspectives

Polyethylene oxide (PEO)-based solid polymer electrolytes (SPEs) with good electrochemical stability and excellent Li salt solubility are considered as one of the most promising SPEs for solid-state lithium metal batteries (SSLMBs). However, PEO-based SPEs suffer from low ionic conductivity at room temperature and high interfacial resistance with the electrodes due to poor interfacial contact, seriously hindering their practical applications. As an emerging technology, in-situ polymerization process has been widely used in PEO-based SPEs because it can effectively increase Li-ion transport at the interface and improve the interfacial contact between the electrolyte and electrodes. Herein, we review recent advances in design and fabrication of in-situ polymerized PEO-based SPEs to realize enhanced performance in LMBs. The merits and current challenges of various SPEs, as well as their stabilizing strategies are presented. Furthermore, various in-situ polymerization methods (such as free radical polymerization, cationic polymerization, anionic polymerization, etc.) for the preparation of PEO-based SPEs are summarized. In addition, the application of in-situ polymerization technology in PEO-based SPEs for adjustment of the functional units and addition of different functional filler materials was systematically discussed to explore the design concepts, methods and working mechanisms. Finally, the challenges and future prospects of in-situ polymerized PEO-based SPEs for SSLMBs are also proposed.