Doping And Surface Modification Of Lini <sub> 0.2 </ Sub> Co <sub> 0.2 </ Sub> Mn <sub> 0.6 </ Sub> O <sub> 2 </ Sub> Synthesis And Electrochemical Performance The Impact

In the paper, the development of rechargeable lithium ion batteries and cathode materials were reviewed in detail.The aims of the present study were to focus on the preparation processes, the structural characterization, and the electrochemical properties of LiNi0.2Co0.2Mn0.6O2 as cathode materials for rechargeable lithium ion batteries.The cathode material LiNi0.2Co0.2Mn0.6O2 was prepared by co-precipitation method. The effect of reaction temperature, pH and reaction time on the physical performance of Ni0.2Co0.2Mn0.6CO3 Precursor was studied. The results show that the best conditions for synthetic precursor is pH=10.0, T=60℃and stirring time is 1.5h. The effect of sintering temperature and sintering time on the physical performance and electrochemical behavior of LiNi0.2Co0.2Mn0.6O2 was studied and the synthesis conditions were optimized. The results show that with the increase of sintering temperature, the growth of crystal is quickened and the crystal becomes more perfect. And the reunite phenomenon was significant if the temperature is too high. It was also found that the morphology of samples was affected by the specific capacity and cycling performance of LiNi0.2Co0.2Mn0.6O2 varied with different synthesis conditions and precipitant, while the charge-discharge curves were similar. The initial discharge capacity of LiNi0.2Co0.2Mn0.6O2 synthesized on the optimized condition was 148 mAh·g-1,and the capacity retained 134 mAh·g-1 after 30 cycles.The modification of LiNi0.2Co0.2Mn0.6O2 by doping four elements:Y, Ce, Sn, Mg and coating MgO was studied. The effect of the doped content on the structure, morphology and electrochemical properties was investigated. The results indicate that the performance of the synthesized samples vary with doping different elements at different contents. The discharge capacity of Li(Ni0.2Co0.2Mn0.6)0.94Y0.06O2, Li(Ni0.2Co0.32Mn0.6)0.94Ce0.06O2, Li(Ni0.2Co0.2Mn0.6)0.97Sn0.03O2 and Li(Ni0.2Co0.2Mn0.6)0.97Mg0.03O2were 155,158,160 and 155 mAh·g-1,respectively. The capacity retained 146,149,153 and 148mAh·g-1 at 0.1 C after 30 cycles and the capacity retention were 94.2%,94.3%,95.6% and 95.4% respectively. Li(Ni0.2Co0.2Mn0.6)0.97Mg0.03O2 coated MgO of 0.5% delivered 153 mAh·g-1 at 0.1 C and retained 149 mAh·g-1 after 30 cycles, and the capacity retention was 97.3%. The discharge capacity retained 136 mAh·g-1 at 1C after 30 cycles, and the capacity retention was 88.8%. Therefore, the modification of doping metal elements and coating metal oxide gives a good way to improve the electrochemical performance of materials.