Li 0.93[Li 0.21Co 0.28Mn 0.51]O 2 nanoparticles for lithium battery cathode material made by cationic exchange from K-birnessite

Abstract

Li 0.93[Li 0.21Co 0.28Mn 0.51]O 2 nanoparticles with an R-3m space group is hydrothermally prepared from Co 0.35Mn 0.65O 2 obtained from an ion-exchange reaction with K-birnessite K 0.32MnO 2 at 200 °C. Even at a hydrothermal reaction temperature of 150 °C, the spinel (Fd3m) phase is dominant, and a layered phase became dominant by combining an increase in the temperature to 200 °C with an increase in lithium concentration. The as-prepared cathode particle has plate-like hexagonal morphology with a size of 100 nm and thickness of 20 nm. The first discharge capacity of the cathode is 258 mAh/g with an irreversible capacity ratio of 22%, and the capacity retention after 30 cycles is 95% without developing a plateau at ∼3 V. Capacity retention of the cathode discharge is 84% at 4C rate (=1000 mA/g) and shows full capacity recovery when decreasing the C rate to 0.1 C.