A Simple Gas–Solid Treatment for Surface Modification of Li‐Rich Oxides Cathodes

Abstract

Li-rich layered oxides with high capacity are expected to be the next generation of cathode materials. However, the irreversible and sluggish anionic redox reaction leads to the O₂ loss in the surface as well as the capacity and voltage fading. In the present study, a simple gas-solid treatment with ferrous oxalate has been proposed to uniformly coat a thin spinel phase layer with oxygen vacancy and simultaneously realize Fe-ion substitution in the surface. The integration of oxygen vacancy and spinel phase suppresses irreversible O₂ release, prevents electrolyte corrosion, and promotes Li-ion diffusion. In addition, the surface doping of Fe-ion can further stabilize the structure. Accordingly, the treated Feox-2 % cathode exhibits superior capacity retention of 86.4 % and 85.5 % at 1 C and 2 C to that (75.3 % and 75.0 %) of the pristine sample after 300 cycles, respectively. Then, the voltage fading is significantly suppressed to 0.0011 V per cycle at 2 C especially. The encouraging results may play a significant role in paving the practical application of Li-rich layered oxides cathode.