| Because of the high charge/discharge capacity and low cost,the LiNi0.5Co0.2Mn0.3O2(NCM523)is one of the research hotspots of cathode materials used in electric vehicles.This thesis aims at improving the poor charge/discharge capacity and low capacity rentention during cycling at high rate and temperature through coating with Al2O3 and LiAlO2 respectively,doping with rare earth elements and granulation by the improved sol-gel process.Discuss the influence rules of the abovementioned processes.The main results are as following:(1)The continuous coating of Al2O3,LiAlO2 has been formed on the surface of NCM523 by the improved sol-gel method.The results showed: when the temperature was 50 ?,the 100 th discharge capacities of NCM523,0.2 mol% Al2O3 and 0.4 mol% LiAlO2 samples were 60.8 mAh/g,98.02 mAh/g,107.45 m Ah/g,the capacity rententions were 52.9%,69.8%,75.5% at 3 C rate,respectively.(2)The two granulation methods of submicron NCM523 are fluidized bed and compaction sintering.The granulation of 0.4 mol% LiAlO2 coating sample with compaction sintering got better electrochemical performance.When the temperature was 50 ?,the 150 th discharge capacity was 135.1 mAh/g at 3 C rate,with a 37.8% increase comparing to the ungranulated sample,the capactiy rentention was 85.4%.(3)The LiNi0.5-xCo0.2Mn0.3NdxO2(x=0.0025,0.004,0.006,0.008)cathode material was synthesized by doping Nd with the improved sol-gel method.When x=0.004,it showed better performance.When the temperature was 50 ?,the 300 th discharge capacity was 102.6 mAh/g at 3 C rate and the capacity rentention was 83.7%.(4)Nd-NCM523-LiAlO2 was synthesized by doping Nd,then coated by LiAlO2,granulated with compaction sintering method.When the temperature was 50 ?,the sample's 300 th discharge capacity was 127.1 mAh/g at 3 C rate,the capacity rentention was 88.3%.When the temperature was 50 ?,the sample's 300 th discharge capacity was 101.9 mAh/g at 5 C rate,the capacity rentention was 89.4%. |
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