Optimal synthetic conditions for a novel and high performance Ni-rich cathode material of LiNi0.68Co0.10Mn0.22O2

Abstract

Layered Ni-rich oxides (LiNi_xCo_yMn_zO₂) are considered as the most promising cathode materials for lithium ion batteries because of their high discharge capacity, high Li⁺ ion deintercalation/intercalation potential, and low cobalt content. However, because of the similar ionic radius of Li⁺ (0.76 Å) and Ni²⁺ (0.69 Å), the Ni-rich cathodes often suffer from poor cycling stability because of the serious cation mixing, and the poor interfacial/structural stability during the electrochemical process. In this work, the effects of sintering temperature, sintering time and excess lithium amount on the structure, morphology and electrochemical performance of a novel spherical high Ni-rich cathode material LiNi_0.68Co_0.10Mn_0.22O₂ cathode are systematically investigated. The results indicate that a sintering temperature of 780 °C with a sintering time of 16 h and an excess lithium amount of 5 wt% could achieve a more stable and lower cation mixing degree LiNi_0.68Co_0.10Mn_0.22O₂ cathode. It delivers a reversible discharge capacity as high as 197.4 mA h g⁻¹ at C/10, and exhibits a capacity retention of 95.9%, 90.2% and 83.5% at C/3, 1C and 3C after 200 cycles at cut-off voltages of 2.7–4.4 V, respectively. These results demonstrate that the optimized LiNi_0.68Co_0.10Mn_0.22O₂ is a promising cathode material for high energy density lithium ion batteries.