Preparation And Modification Of Lithium-rich Manganese-based Cathode Material Li_1.2Ni_0.15Co_0.15Mn_0.5O₂

Layered lithium-rich manganese-based cathode materials are considered to be the most promising cathode materials for lithium-ion batteries due to their advantages of high energy density,green environmental protection and low production cost.However,lithium-rich manganese-based materials themselves have many problems,such as low first coulomb efficiency,fast voltage decay,and poor rate performance,resulting in their inability to achieve commercial development.In this paper,the preparation process of lithium-rich manganese-based materials was optimized,and the optimal synthesis conditions of Li_1.2Ni_0.15Co_0.15Mn_0.5O₂ materials were obtained.In view of the problems existing in lithium-rich manganese-based materials,this paper improves the electrochemical performance of the materials by doping Ta and adding agar.The main research contents are as follows:（1）Li_1.2Ni_0.15Co_0.15Mn_0.5O₂ was prepared by sol-gel method.The preparation process of materials was optimized,and the effects of p H,drying temperature,calcination temperature and calcination time on the properties of the materials were studied.The results showed that the material had the best properties under the conditions of p H=7,drying temperature of 140°C,pre-burning temperature of 450°C,final burning temperature of 850°C and final burning time of 10 h.At 0.1 C,the discharge specific capacity of the first circle was 265.6 m Ah·g^-1,and the first effect was 81.2%.After 100 charge-discharge cycles at 0.5 C,the capacity retention rate was59.4%.（2）On the basis of the optimal synthesis conditions,the sol-gel method was used to incorporate Ta elements into the bulk phase of Li_1.2Ni_0.15Co_0.15Mn_0.5O₂ materials,and the influence of different Ta doping amounts on the materials was explored.The results showed that when the Ta doping content was 4%,its performance was the best.At 0.1 C,the discharge specific capacity of the first circle was 250.1 m Ah·g^-1.After100 charge-discharge cycles at 0.5 C,there was a capacity of 141.1 m Ah·g^-1,with a capacity retention rate of 65.5%.（3）For the first time,Li_1.2Ni_0.15Co_0.15Mn_0.5O₂ materials were synthesized by agar-assisted sol-gel method,and the effects of different amounts of agar added on the materials were explored.The results showed that the agar added at 10%performed best.At 0.1 C,the discharge specific capacity of the first circle was 260.2 m Ah·g^-1.After 100 cycles of charge-discharge cycles at 0.5 C,there was still a capacity of145.3 m Ah·g^-1,and the capacity retention rate was as high as 70.0%,which was 25.4%higher than that of the original material.