Study Of The Cathode Material LiNi_0.5Mn_0.3Co_0.2O₂for Lithum Ion Battery

Due to the expensive price, toxcity and low capacity of the LiCoO2, more andmore reasearchers devote themslves to study new canthod materials of lithum ionbatteries. LiNixMnyCo1-x-yO2has higher capacity and stabler structure among thecanthod materials of lithum ion batteries, so it is a promising alternative cathodmaterials of lithum ion batterie. In the paper, the LiNi_0.5Mn_0.3Co_0.2O₂is the studyobject. And the most studies is on the synthesis of Ni_0.5Mn_0.3Co_0.2（OH）₂, thepreparation of the LiNi_0.5Mn_0.3Co_0.2O₂and the doping study on the material.In this paper, the Ni_0.5Mn_0.3Co_0.2（OH）₂is synthesized by co precipitation.westudy the influence of technological parameter to the performance of theNi_0.5Mn_0.3Co_0.2（OH）₂.The technological parameter includes the stiring speed, theconcentration of solution, pH, temperature, the solution adding rate, theconcentration of ammonia and the reaction time.We selected the best parameterthrough the morphology, the molar mass ratio of the three metal and the particle sizedistribution. the best preparation parameters is that the stiring speed is600r/min, thesolution concentration is2.0mol/L, pH is10.5, the temperature is55℃,the solutionadding rate is10.0ml/min, the concentration ratio between the metal sulfates andammonia is1:0.75, the reaction time is6hours. The particle we got is uniform andhas the best surface morphology,and the three metal molar ratio approximates5:3:2.In this paper, we used the precursor the company uses as the raw material. Westudy the effect of the Li/M and the calcination temperature to the performance ofthe LiNi_0.5Mn_0.3Co_0.2O₂. by the test means,such as SEM, XRD, the particle sizedistribution and the electrochemistry test means, we got that the best ratio of Li/Mis1.03:1. And the material has the best cycling performance in the800℃，thecapacity retention is96.4%. the material has the highest capacity in the900℃,thecapacity is189.5mAh/g.In this paper, on the base of Li/M=1.03and850℃, we study the dopingmodification of the LiNi_0.5Mn_0.3Co_0.2O₂.the kinds of the doping include Ti、Mg、F、Ti+F and Mg+F. by the test means,such as SEM, XRD, the particle size distributionand the electrochemistry test means,we find that if the doping mass is low, it has thelower capacities than no doping material, but it has the better cycling performance.Among the doping kinds, the Ti doping material has the best cycling performanceand has no capacity loss. The initial discharge capacity is185.0mAh/g. and thecapacity retention is93.4%after200charge-discharge cycles。...