Recent progress and perspectives of lithium-rich manganese-based cathodes for high-energy-density solid-state batteries.

All-solid-state batteries (ASSBs) with lithium-rich manganese-based materials (LRMs) are considered promising next-generation energy storage systems. The LRM cathodes deliver a high specific capacity of more than 250 mAh g-1 and a theoretical energy density of 900 Wh kg-1 based on the active material mass, deriving from simultaneous cationic and oxygen redox. However, their practical application is hindered by the notoriously irreversible release of oxygen, poor rating capability, voltage decay, and degradation of the cathode-electrolyte interface. In this paper, the structural characteristics, high-capacity mechanisms, and development of LRM-based solid-state batteries are systematically reviewed. Furthermore, the interfacial behavior between LRMs and electrolytes is highlighted, determining the electrochemical performance of batteries. Additionally, emerging machine learning is introduced for accelerating the design and performance optimization of LRMs. Finally, future directions are outlined toward high-energy-density LRM-based ASSBs. It is believed that this review will provide a valuable guide to inspire the application of high-energy-density LRM-based ASSBs.