Reaearch On The Electrochemical Properties Of Nickel-cobaltmanganese Ternary Cathode Materials

Due to the high energy density and cost advantages, Ni-rich ternary layered oxide LiNixCoyMnzO2(x>0.5, abbreviated as NCM) has become the focus of the next generation of lithium-ion battery cathode material. In practical applications,in order to obtain a higher energy density, the simplest approach is to increase the cut-off voltage, but the nickel-rich oxide is accompanied by rapid capacity decay at high pressure (>4.3 V), so poor high pressure performance Hindering the application prospect of Ni-rich ternary layered oxide. In order to get a better electrochemical performance battery, three types of method have been taken to prepare LiNi0.6Co0.2Mn0.2O2 (abbreviated as NCM622) in the research work.In the first part,porous LiNi0.6Co0.2Mn0.2O2 was successfully prepared by coprecipitation method, and the influence of aging time and lithium content was discussed. The results showed that the degree of lithium excess was 50% and the aging time was 12 h, the degree of cation mixing was small and the layered structure was maintained well. The specific performance of 1 C (1 C=200 mA/g),2 C, 5 C, 10 C rate is 144 mAh/g, 130 mAh/g, 112 mAh/g, 89 mAh/g. The electrochemical performance test shows that the rate capacity of the material is better because of the maintenance of a porous morphology.In the second part, spherical LiNi0.6Co0.2Mn0.2O2 material was prepared by urea homogeneous precipitation method. The results show that the other anions are difficult to precipitate the LiNi0.6Co0.2Mn0.2O2 material in the pure urea system except that the effect of Ac2-self-assembly is weak. Through change the pH and PVP-assisted water thermal reaction, the correct LiNi0.6Co0.2Mn0.2O2 material can be produced At pH=9, the initial discharge capacities at 0.1 C, 1 C,2 C rate are: 163 mAh/g, 142 mAh/g, 102 mAh/g, respectively. The energy retention rates after 50 cycles are: 91%, 93%, 92%. The first discharge capacity of 160℃ PVP assisted hydrothermal method at 1 C rate is 134 mAh/g, the capacity retention after 50 cycles is 80%, it reaches a certain increase compared to pure urea system 68%.In the third part, LiNi0.6Co0.2Mn0.2O2 material with certain morphology was prepared by template method. The results show that the spherical template structure is more stable than the flower template structure, and the LiNi0.6Co0.2Mn0.2O2 material with spherical NiO as template is successfully synthesized. After the high temperature sintering, the spherical morphology can be successfully maintained, the initial discharge specific capacities at 0.1 C, 1C and 2 C rate are: 165 mAh/g, 117 mAh/g and 93 mAh/g, respectively. The energy retention after 50 cycles is 88% 84% and 82%, respectively.