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.