Synthesis And Electrochemically Improvement Of Spinel Lithium Manganese Oxide Materials

Lithium-ion battery is a new type of secondary batteries developed during 1990's. Spinel manganese oxide (LiMn₂O₄) has caused much attention for the application in electric vehicles, since its low cost and smaller impact on environment. However, its capacity fades slowly, and this prevents its wide commercial use. This fading is mainly due to the following three factors: dissolution of Mn3+,Jahn-Teller effect and dedcomposition of the organic solvents. To improve the electrochemical performance of LiMn₂O₄, a sol-gel method, adulteration (doping) and surface modification were used in this thesis. The main work of the research was as follows:1. The active cathode materials, Li1+yMxMn2-yO4 (M = Al,Co,Ni,Zn) powders were synthesized by sol-gel method. The influence of different doping elements on the structural properties of the as-prepared samples was investigated by XRD, IR and SEM.2. Using the conductive sol SnO2: Sb, ZnO: Al as the raw materials, SnO2: Sb or ZnO: Al was homogeneously coated on LiMn₂O₄ by sol-gel method. In this way, the oxide effectively prohibited the direct contact LiMn₂O₄ with the electrolyte. The results showed the coated LiMn₂O₄ could give good electrochemical performances.