Study On Surface Modification Of Li(ni_0.73co_0.12mn_0.15)O₂ Cathode Material

Cathode material Li(Ni0.73Co0.12Mn0.15)O2 is a promising candidate for the new generation of lithium ion batteries due to its high theoretical specific capacity, safety performance and high voltage (4.3 V vs. Li/Li+). However, its cyclic performance and electrochemical properties under high voltage need to be improved. Moreover, PH value on the surface of Li(Ni0.73Co0.12Mn0.15)O2 is too high, which leads to water easily absorbed in the process of slurry preparation and then battery electrochemical performance becomes worse. In this paper, Li2ZrO3 and Kh-560 coated Li(Ni0.73Co0.12Mn0.15)O2 materials were prepared by hydrothermal method and their electrochemical performance were investigated.The mechanism of coating layer on Li(Ni0.73Co0.12Mn0.15)O2 was explored by controlling the amount of Li2ZrO3. The experimental results show that the thickness of Li2ZrO3 coating layer is about 15 nm when the calcination temperature is 500 ?and sintering time is 5 h.Li2ZrO3 coating layer makes the Li+ ions more likely to deintercalate in charging and discharging process and the cationic mixed degree of cathode is improved. Charging and discharging test results show that the Li2ZrO3 coating layer not only improved the rate and long cycle performance of Li(Ni0.73Co0.12Mn0.15)O2 material under the normal and high voltage, but also enhanced the capacity retention of the cathode. The coating material showed excellent performance especially with the amount of 5% wt Li2ZrO3 coated.The mechanism of Kh-560 coating layer on Li(Ni0.73Co0.12Mn0.15)O2 was investigated by controlling the amount of coating layer. The experimental results show that the thickness of Kh-560 coating layer is about 15 nm when the thermal treatment temperature is 200 ? and sintering time is 4 h. Kh-560 coating layer may provide a fast electron transport channel,making electron easier to transfer during charging and discharging process. Charging and discharging test results show that the Kh-560 coating layer improved the rate and long cycle performance and capacity retention of Li(Ni0.73Co0.12Mn0.15)O2 material. The coating improved the performance of material most obviously with the amount of 0.5% Kh-560.Hydrophobicity test was conducted for Li(Ni0.73Co0.12Mn0.15)O2 materials with and without Kh-560 coating layer. The experimental results show that Kh-560 can effectively prevent Li(Ni0.73Co0.12Mn0.15)O2 from absorbing water and the coated Li(Ni0.73Co0.12Mn0.15)O2 displayed better electrochemical performance in the same environment. So Kh-560 coating layer can improve the storage performance of Li(Ni0.73Co0.12Mn0.15)O2.