Research On Surface Modification And Electrochemical Performance Of LiNi_xCo_yMn_1-x-yO₂

Recently, LiCoO2 has been widely used as cathode active material in commercialized lithium ion batteries. While due to the high cost and the cobalt lacks of resource, LiCoO2 is very difficult to meet the development demands of Li-ion battery. Layer-structured LiNixCoyMn1-x-yO2 compound has been reported to be a potential and promising cathode material to replace LiCoO2 for rechargeable lithium ion batteries due to its low cost, low pollution and high capacity.In this paper, the typical layered LiNi0.5Mn0.5O2 and LiNi1/3Co1/3Mn1/3O2 were studied by doping and coating.Firstly, the layered Li(Ni0.5-xAl2xMn0.5.x)O2 (x=0.0 and 0.1) (Mn/Ni=1) were synthesized by sol—gel method using citric acid as a chelating agent. The structure, electrochemical properties of prepared cathode materials were measured by means of X-ray diffraction, cyclic voltammetry, galvanostatic charge-discharge test and AC impedance spectra. The measured results indicate that, compared to LiNi0.5Mn0.5O2, the electrochemical properities of Li(Nio.4Al0.2Mn0.4)O2 are evidently improved.Afterwards, the layered material of LiNi1/3Co1/3Mn1/3O2with a-NaFeO2 structure is synthesized by a fast wet-chemical process with citric acid as the chelating agent. The effects of Al-doping and 1.0wt% Cr2O3 coating on structure and the electrochemical properities of LiNi1/3Co1/3Mn1/3O2 were investigated by using X-ray diffraction(XRD), scanning electron microscope (SEM), charge-discharge tests, cyclic voltammetry(CV) and electrochemical impedance spectra (EIS).