Study On Preparation And Properties Of Li-ion Battery Anode Materials Li₄Ti₅O₁₂

The graphite-type carbon anode material has been widely used in the commercial lithium ion batteries, but its irreversible capacity loss is high and there is a potential safety problem. Spinel Li₄Ti₅O₁₂ as a new anode material for lithium-ion battery almost has no changes in the structure when charged and discharged and it has been called as "zero strain" material.Li₄Ti₅O₁₂ has excellent cycle performance and plateau voltage and so on.The safety and reliability of the material are improved greatly as compared with carbon electrode.In this thesis, the solid-state method and doping modification of spinel Li₄Ti₅O₁₂ anode materials were researched. The thesis focused on the improvement of the electrochemical properties of the Li₄Ti₅O₁₂ material doped by elements such as Mg,Al and Cu,the influences to Li₄Ti₅O₁₂ were studied with different doping ratio and doping elements, and their optimal synthetic process was studied. The samples were characterized and researched by XRD and laser particle size analyzer to get the images of their crystal structures and the particle size distribution. Moreover, the electrochemical properties of the doped products were studied by charge-discharge curves and cycle number. The experiment result indicated that Li₄Ti₅O₁₂ material synthesized at 700-900℃for 15-24h could enhance the electrode rate capabilities. However, overlong heat treatment and higher calcination temperature would result in the aggregation of particles and lead to a poor electrochemistry performance.As far as Li_4-xMg_xTi₅O₁₂ was concerned, it was found that the x=0.1 has a good electrochemistry performance and size distribution,the first discharge special capacity was 175.8, 151.5, 140.3, 121.3mAh/g at 0.5C, 1C, 5C, 10C rate, respectively. It was found that the high rate capability of Li₄Ti₅O₁₂ doped by magnesium had been improved.At 0.1C discharging rate, the first discharge specific capacities of Li4-xAlxTi5O12(x=0.05, 0.1, 0.2 and 0.3) were found to be 135.5mAh/g ,138.8mAh/g, 141.2mAh/g and 150.6mAh/g respectively. The capacity of the Li₄Ti₅O₁₂ doped by Al had not been improved, but cycle stability was enhanced, compared to the pristine Li₄Ti₅O₁₂. For Li₄Ti₅O₁₂/CuO, the discharge special capacity was 228.7, 173.3, 159.8, 144.3 mAh/g at 0.5C, 1C, 5C, 10C rate, respectively. The Cu additive effectively improved the cycle stability and electrochemical performance of the pristine Li₄Ti₅O₁₂.