Understanding lithium-rich manganese-based cathode materials from the perspectives of lattice challenges and doping engineering

Li-rich manganese-based (LRMO) cathodes offer high capacity, voltage, and Mn content, forming a high-energy/low-cost/high-safety triad that positions them as the pivotal solution to surpass current Li-ion battery limits. However, structural and electrochemical degradation during cycling constitute the primary commercialization barriers. The lattice governs the two core electrochemical processes: (1) Li+ occupation/migration and (2) transition metal (TM)/oxygen valence changes. These collectively determine charge transport, capacity, and stability through lattice and electronic dimensions. Doping engineering enables addressing the challenges fundamentally from the material’s intrinsic lattice. This review examines LRMO cathodes through lattice challenges and doping engineering. Two phase structure models exist: solid solution vs. two-phase composite. The initial charge features a sub-4.5 V ramp followed by a ~4.5 V plateau, corresponding to LiTMO2 (Ni2+/Ni4+, Co3+/Co4+ redox) and Li2MnO3 (Mn3+/Mn4+, O2−/O2 redox) activation, explained by Li+/H+ exchange, oxygen loss, mixing mechanism or multi-step mechanisms. Critical lattice challenges include the Jahn-Teller effect and unfavorable phase transitions, dissolution and migration of TM ions, cation mixing phenomena, and surface irreversible lattice oxygen release, causing low initial Coulombic efficiency, rapid capacity fading, poor rate capability, and drastic voltage decay. Doping the high-valence and large ionic radius metal ions is a mainstream strategy to inhibit Jahn-Teller effect and cation mixing, respectively. The key to inhibiting TM dissolution and oxygen release via ion doping lies in strengthening metal-oxygen bonds, and modulating O2p orbitals, respectively. Finally, the emerging challenges and future research about LRMO cathodes are proposed.