Rheological phase method synthesis of carbon-coated LiNi_0.6Co_0.2Mn_0.2O₂ as the cathode material of high-performance lithium-ion batteries

Abstract

Material synthesis plays an important role in determining the performance and cost of final devices. In this paper, rheological phase method has been applied to conveniently synthesize carbon-coated LiNi_0.6Co_0.2Mn_0.2O₂ (LNCM622/C) as the cathode material of high-performance lithium-ion batteries (LIBs), avoiding the use of co-precipitation route with complicated procedures and environmental issues. Importantly, the addition of citric acid enabled a relative low temperature of crystallization initiation of the reaction of forming LNCM622/C, which is crucial for the material synthesis. As a result, highly ordered LNCM622/C materials have been obtained with a final calcinating temperature of 900 °C, which is comparable to that being used in co-precipitation route. It is worth mentioning that the synthesis reaction was processed in air without the extra-oxygen gas supply. By varying lithium contents (Li/TM = 0.95, 1.00, 1.05, 1.10, 1.15, and 1.20 by molar, TM = Ni, Co, and Mn), the structure and morphology of resulted LNCM622/C materials were changed, leading to different electrochemical performances of corresponded LIBs. It was found that the Li/TM = 1.15 sample had the best initial discharged capacity at 0.1 °C rate (177.1 mAh g^− 1), whereas the Li/TM = 1.05 sample showed the best cycling and rate performance (100.6 mAh g^− 1 at 1 °C) among synthesized samples. Overall, these results suggest that rheological phase method can be considered as an effective route for synthesizing carbon-coated LiNi_0.6Co_0.2Mn_0.2O₂ cathode materials for high-performance LIBs.