One-Step Integrated Comodification to Improve the Electrochemical Performances of High-Voltage LiCoO₂ for Lithium-Ion Batteries

Abstract

While the theoretical capacity of LiCoO2 is as high as 274 mA h g–1, its practical specific capacity is only about 140 mA h g–1 when it was first applied in lithium-ion batteries. Raising the charging cutoff voltage can effectively enhance the specific capacity of LiCoO2. For example, when increasing the cutoff voltage to 4.5 V vs Li+/Li, the specific capacity will increase to 185 mA h g–1. However, the surface and structure instability of LiCoO2 under high-voltage operation lead to rapid capacity decay. Various modified strategies have been proposed, such as element doping and surface coating. In this work, we develop a one-step integrated comodification approach to achieve a long cycle life of LiCoO2 in the range of 3.0–4.5 V. The phosphate surface layer suppresses the side reaction of electrolyte and Co dissolution. Mn doping enhances the structure stability of LiCoO2. The capacity retention of a modified LiCoO2 with a cutoff voltage of 4.5 V is as high as 83.7% even after 700 cycles.