Study On Effect Ot Al₂O₃ Coating On The Electrochemical Performance Of Lithium-rich Cathode Materials

xLi2MnO3·(1-x)LiMO2(M=Mn,Ni,Co)Lithium-rich cathode material has become a popular cathode material because of its high specific capacity,good cycle stability,suitable discharge voltage range and low cost.However,a series of problems such as low Coulomb efficiency in the first cycle,serious irreversible capacity loss,voltage attenuation and problems of cycle performance have become its own limiting factors.In order to solve the above problems,lithium-rich cathode materials were prepared by spray drying method and modified by Al2O3 coating to improve the electrochemical performance of the materials.The main research work and achievements are as follows:1.The material has been successfully prepared by spray drying method and the sintering temperature parameters have been researched.(1)The materials prepared by different temperatures exhibit well-ordered hexagonal layered structure,good crystalline structure,good crystallinity and high purity.(2)The morphologies of powder particles are small in size,nearly spherical,uniform distribution,good dispersion,smooth surface and less aggregation.(3)The materials prepared by 800? exhibit relatively good comprehensive electrochemical performance and structural stability in terms of initial charge-discharge performance,mid-point voltage attenuation,cyclic performance,electrochemical impedance and cyclic voltammetry characteristics.2.Al2O3-coated materials were successfully prepared by alkoxide hydrolysis liquid phase coating method,and the coating amount of Al2O3 was researched.(1)Al2O3 coating doesn't change the hexagonal layered structure of materials,and it enables the material to obtain layered structure with better cationic ordering.(2)The material coated with 0.9 wt.%Al2O3 exhibits relatively good characteristics in the morphology,thickness,continuity and uniformity of the coating.(3)Al2O3 coating can effectively improve the comprehensive electrochemical performance of materials.The materials with 0.9 wt.%exhibit relatively good comprehensive electrochemical performance on initial charge-discharge performance,mid-point voltage attenuation,cycling performance and electrochemical impedance.