Manganese‐Based Spinel Cathodes: A Promising Frontier for Solid‐State Lithium‐Ion Batteries

Abstract Recently, all‐solid‐state lithium‐ion batteries (ASSLIBs), which exhibit improved safety and enhanced energy density compared to conventional commercialized lithium‐ion batteries (LIBs), thereby have garnered extensive research interest. Among the promising cathode candidates, Mn‐based spinel cathodes LiMn 2 O 4 (LMO) and LiNi 0.5 Mn 1.5 O 4 (LNMO), with the unique characteristics of low cost, structural stability, and 3D Li‐ion diffusion channels, have demonstrated excellent performance in LIBs and presented great potential in ASSLIBs applications. However, several challenges, including structural degradations, poor interfacial contact, large interfacial resistance, and Mn‐dissolution/diffusion during the electrochemical cycling, hinder their practical applications and commercialization in the ASSLIBs. Particularly, the high‐voltage LNMO cathodes suffer from the challenge of electrochemical incompatibility with most of the solid‐state electrolytes (SSEs). Herein, the spinel structure, the electrochemical behavior, and the structural degradation of the LMO/LNMO are explored. The characteristics and recent progress of the mitigating strategies to the challenges of various SSEs, including polymer‐, oxide‐, composite‐, sulfide‐, halide‐, and LiPON‐based SSEs, are introduced when paired with LMO/LNMO. Finally, the directions for future research to advance Mn‐based spinel cathodes and fulfill the requirements of the next‐generation ASSLIBs are also discussed.