Research On The Synthesis And Properties Of Layered LiNi_xCo_yMn_1-x-yO₂

Along with the increase of energy and environment problems, and the rapid development of modern science and technology, how to increase the performances of the lithium ion batteries (LIBs) becomes more and more important. LIB is the first choice for the high working voltage, long cycle life, high energy density and amity to the enviroment. The cathode material is the bottle-neck of the development of lithium ion batteries, so researches on the new anode materials with low cost and high capacity are the developing trend of the society. In order to overcome the disadvantages of high cost and low energy of conventional anode materials, multi-composite cathode materials with low cost and high energey are made by a doping method.In this paper, LiNi_xCo_yMn_1-x-yO₂ material, having the same layered structure (α-NaFeO₂ R3m group) with LiCoO₂, was made by co-precipitation method at different conditions with different calcination way, calcination temperature, calcination time, Ni/Co/Mn ratio and pH value. And then studies were performed on how the factors influenced the structure and electrochemical performances of the new materials. Optimizing the material of LiNi_xCo_yMn_1-x-yO₂ synthetic process, which provides science basis for industrialization of the material of LiNi_xCo_yMn_1-x-yO₂. Precipipation made at pH 8～9, dried for 12h, calcined at 500℃for 6h and 850℃for 12h is the optimal condition,which was confirmed by XRD,SEM and the constant current charge-discharge test.Among the kinds of materials, Li(NiMn)_0.4Co_0.2O₂,LiNi_1/3Co_1/3Mn_1/3O₂ and Li(MnCo)_0.25Ni_0.5O₂,Li(MnCo)_0.15Ni_0.7O₂ exhibited good layered structure by XRD, and which has excellent electrochemical capacity by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and constant current charge-discharge test. Thereinto, the Li(NiMn)_0.4Co_0.2O₂ material had an initial discharge specific capacity of 124.1 mAh·g^-1 and retaining above 90% after 30 cycles; Li(MnCo)_0.15Ni_0.7O₂ material had the highest secific capacity of 133 mAh·g^-1, but retaining only 80.4% after 30 cycles; The intial discharge specific capacity of LiNi_1/3Co_1/3Mn_1/3O₂ and Li(MnCo)_0.25Ni_0.5O₂ were both above 120 mAh·g^-1, retaining about 85%. So LiNi_xCo_yMn_1-x-yO₂ is a promising cathode material that can be put into use.