Overcoming the Challenges of 5 V Spinel LiNi_0.5Mn_1.5O₄ Cathodes with Solid Polymer Electrolytes

High-voltage spinel manganese oxide LiNi0.5Mn1.5O4 (LNMO) that possesses high energy densities, high thermal and electrochemical stabilities, good operating safeties, low costs, and good rate performance has been well recognized to have great potential for power batteries. Despite these merits, unqualified electrolytes are still a big obstacle toward mass production of LNMO-based lithium-ion batteries (LIBs). To address this obstacle, solid polymer electrolytes (SPEs) have been increasingly considered as promising candidates thus far. Here, we mainly discuss the inherent advantages and ideal requirements of SPEs coupling with LNMO cathodes and then systematically review the recent advances of SPEs from the perspective of structure–performance relationships for the first time. Finally, prospects and challenges of the SPE systems are also discussed. This Review aims to guide rational structure design and future development of state-of-the-art SPEs with high anodic stabilities, boosting the practical applications of high-voltage LNMO cathode-based LIBs.