Preparation of low cobalt-doped LiNiO2 materials by the spray pyrolysis method

Abstract

LiNiO2 (LNO) is recognized as the most promising cathode material for next-generation lithium-ion batteries owing to its highest energy density and economic benefit in the layered oxide cathode materials systems. However, severe cation disordering, multiple phase transformations and poor lithium-ion diffusion kinetics, which result in rapid degradation of cycling stabilities and rate properties, hinder its further practical applications. Cobalt doping is an effective strategy to address such issues, but the influences of cobalt on LNO materials have not been figured out completely yet. Hence, a systematical investigation of cobalt doping for LiNiO2 cathode materials prepared by spray pyrolysis is conducted. The addition of cobalt enhances the stabilities of layered structures and suppresses the cation disordering effectively. The multiple-phase transformations during cycling are also alleviated significantly. Furthermore, cobalt doping can decrease charge transfer resistances and improve lithium-ion diffusion kinetics, especially at high de-lithiation states. As a result, the electrochemical performances are improved comprehensively after cobalt doping. The LNO with optimal doping amount exhibits an improved capacity retention of 78.0% after 100 cycles as compared with 64.9% for pristine LNO, and an outstanding rate performance of 167.2 ​mA ​h ​g−1 with the current density of 5 ​C (1 ​C ​= ​200 ​mA ​g−1).