Surface modification of Li−rich manganese−based cathode materials by chemical etching
Lithium−rich layered oxides are attractive high−energy cathode materials for lithium−ion batteries but suffer from structural instability that incurs voltage fading, capacity loss, and poor kinetics. Here we report the synthesis of Li1.2Mn0.52Co0.13Ni0.13O2 (LMCN) through co−precipitation method and the performance improvement of LMCN with ceric ammonium nitrate (CAN) etching. Combining X−ray diffraction, scanning electron microscope and X−ray photoelectron spectroscopy reveals that chemical etching modifies the surface composition and generates a thin amorphous layer, which mitigates structural collapse and lattice oxygen release. Compared with pristine LMCN, the etched sample exhibits improved capacity retention (from 58.7% to 76.6% after 200 cycles at 1 C) and rate capability (from 125 to 140 mAh g−1 at 5 C). The results suggest that chemical etching is an efficient strategy to enhance Li−rich oxide cathode materials.