Advances and Challenges of Lithium‐Rich Manganese‐Based Cathode Materials for All‐Solid‐State Batteries

All‐solid‐state batteries (ASSBs) have emerged as a leading next‐generation energy storage technology due to their enhanced safety, higher energy density, and nonflammable nature. However, the current development of ASSBs still faces many challenges, including low ionic conductivity of SSEs at room temperature, side reactions of solid‐state electrolytes (SSEs) and electrodes, poor interfacial contact, and internal mechanical stress. To overcome these, the selection and optimization of cathode materials are one of the keys, and lithium‐rich manganese‐based materials (LRMOs) have become a promising cathode material due to their high specific capacity (>250 mAh g −1 ), high energy density (>900 Wh kg −1 ), and low cost. However, the problems of lattice oxygen loss, voltage fading, low initial Coulombic efficiency (ICE), and interfacial side reactions of LRMOs and SSEs severely limit their practical applications. This review provides a detailed overview of the basic properties of LRMOs and the challenges faced in their application in ASSBs. It summarizes and analyzes the relevant advances in solving the application of LRMOs in ASSBs and finally concludes and looks forward to the future optimization focus and development direction of LRMOs in ASSBs.