Rheological phase method synthesis of carbon-coated LiNi0.6Co0.2Mn0.2O2 as the cathode material of high-performance lithium-ion batteries

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 LiNi0.6Co0.2Mn0.2O2 (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 LiNi0.6Co0.2Mn0.2O2 cathode materials for high-performance LIBs.