Preparation And Modification Of Li_1.2Mn_0.54Ni_0.13 Co_0.13 O₂ As Cathode Material For Lithium Ion Batteries

Compared with conventional cathode materials for lithium ion batteries, the layered Li-rich material Li1.2Mn0.54Ni0.13Co0.13O2 has many merits, such as higer capacity, lower toxicity, and lower cost, and so on. The material can deliver an initial discharge capacity as high as 250mAh/g when the cut-off voltage is over 4.5V, however, the material has an irreversible capacity loss on the initial cycle and bad cycling stability, particularly at higher current rates.In this paper, Li1.2Mn0.54Ni0.13Co0.13O2 with high capacity was prepared by carbonate co-precipitation and solid state reaction methods. The facts such as charging temperature, agitation speed in co-precipitation and the calcining temperature and time in calcining process were optimized to obtain the layered lithium rich oxides with excellent performance. Surface modification with AlF3, CeO2 and C were conducted to improve the reversible capacity and cycling stability. CV and EIS were also used to investigate the mechanism of materials.The spherical Li1.2Mn0.54Ni0.13Co0.13O2 agglomerations with size about 4um and 10um were synthesized by controlling the facts in co-precipitation process. The lithium rich oxides calcinated at 900℃for 12h delivered the initial capacity of this material was 247.2mAh/g, with the capacity retention of 85.1% after 50 cycles between 2.0-4.8V at 28.3 mA/g current density.AIF3, CeO2 and C coating on the surface of Li1.2Mn0.54Ni0.13Co0.13O2 material can improve the coulombic efficiency, cycling stability and rate characteristics.1% AlF3-coating material delivered 249.3 mAh/g,172.3 mAh/g,143.2 mAh/g,101.4 mAh/g at 0.1C,1C,2C, 5C, respectively. CeO2 coating can improve the electrochemical performance of the material at low current density, and 5% C-coating material improved the cycling stability significantly.CV and EIS showed that the surface layered materials converted to spinel structure during AlF3, CeO2 coating proeess. What's more, AlF3, CeO2 coating layers could resist the corrosion of cathode materials in electrolyte and could stabilize the interface layer, resulting in reduced interface impedance and improved electrochemical performance.