The Study Of Cathode Material Of LiNi_xCo_yMn_1-x-yO₂ For Lithium Ion Batterry

Recently, intensive effort has been directed towards development of the newgeneration cathode materials------LiNi_xCo_yMn_i-x-yO₂. In the thesis, LiNi_xCo_yMn_i-x-yO₂cathode materials were successfully prepared by high temperature solid state method and co-precipitation method. The products were studied systematically by XRD, TEM, SEM, particle size analyzer, and the eletrochemical techniques, such as: CV, PVI and EIS. Through optimizing the synthesis conditions of preparing LiNi_xCo_yMn_i-x-yO₂ cathode materials, the products with excellent performance were obtained.The high temperature solid state method was one of the most important methods in preparing cathode materials. LiNi_1/3Co_1/3Mn_1/3O₂ was successfully synthesized at different conditions by the method. Some factors which affected the formation of LiNi_1/3Co_1/3Mn_1/3O₂ crystallites were investigated. With increasing of the calcination times, LiNi_1/3Co_1/3Mn_1/3O₂ with perfect crystallization, homogeneous chemical composition and particle size could be easily obtained. The effects of the holding time and temperature in the second calcination were also discussed. The parameters which directly influenced the electrochemical behavior in lithium cells were systematically studied. The optimum synthetic condition is: 1000℃ and 20hs presented.Another synthesis method, the co-precipitation method, was also proposed in the thesis. The preparation conditions of the precursor LiNi_xCo_yMn_i-x-yO₂ were investigated. For instance, the pH, the amount of the complexing agent, precipitating agent, mixing sequence and mixing speed, etc. The results showed that the optimized conditions in preparing the precursor were pH =11 (precipitating agent: OH^-), ammonia concentration = 0.37 mol/dm³, N₂ atmosphere and stirring speed = 2000 rpm. The...