Molten-Salt-Assisted Strategy Enables High-Rate Micron-Sized Single-Crystal Li-Rich, Mn-Based Layered Oxide Cathode Materials

Li-rich Mn-based layered oxides (LMLOs) are expected to be the most promising high-capacity cathodes for the next generation of lithium-ion batteries (LIBs). However, the poor cycling stability and kinetics performance of polycrystalline LMLOs restrict their practical applications due to the anisotropic lattice stress and crack propagation during cycling. Herein, B-doped micron-sized single-crystal Co-free LMLOs were obtained by molten-salt (LiNO₃ and H₃BO₃)-assisted sintering. The results reveal that the low-melting-point molten salt can serve as liquid-phase media to improve the efficiency of atomic mass transfer and crystal nucleation and growth. The modified single-crystal LMLO cathodes can resist the accumulation of anisotropic stress and strain during the cycling and reduce interface side reactions, thus achieving excellent high-voltage stability and kinetics performance. The reversible specific capacity of the single crystals is 210.8 mAh g^-1 at 1C with a voltage decay rate of 1.95 mV/cycle and up to 161.1 mAh g^-1 at 10C with a capacity retention of 81.06% after 200 cycles.