Tuning Li₂MnO₃-Like Domain Size and Surface Structure Enables Highly Stabilized Li-Rich Layered Oxide Cathodes

Severe capacity/voltage fading still poses substantialobstaclesin the commercial applications of Li-rich layered oxides, which stemsfrom the aggregation of Li2MnO3-like domainsand unstable surface structure. Here, we report highly stabilizedCo-free Li1.2Ni0.2Mn0.6O2 with uniformly dispersed Li2MnO3-like domainsand a protective rock-salt structure shell by reducing the oxygenpartial pressure during high-temperature calcination. Experimentalcharacterizations and DFT calculations reveal that the uniformly dispersedand small-sized Li2MnO3-like domains suppressthe peroxidation of lattice oxygen, enabling highly reversible oxygenredox and excellent structural stability. Moreover, the induced rock-saltstructure shell significantly restrains lattice oxygen release, TMdissolution, and interfacial side reactions, thereby improving theinterfacial stability and facilitating Li+ diffusion. Consequently,the obtained Li1.2Ni0.2Mn0.6O2 which was calcinated under an oxygen partial pressure of0.1% (LNMO-0.1) delivers a high reversible capacity of 276.5 mAh g(-1) at 0.1 C with superior cycling performance (a capacityretention rate of 85.4% after 300 cycles with a small voltage fadingrate of 0.76 mV cycle(-1)) and excellent thermal stability.This work links the synthesis conditions with the domain structureand electrochemical performance of Li-rich cathode materials, providingsome insights for designing high-performance Li-rich cathodes.