Li₄Ti₅O₁₂ Prepared By Sol－gel Method With In-situ Carbon Coating

Lithium ion battery may be one of the most promising power source of electric vehicle as its high energy density, high potential and nonmemeory effect as well.Li-ion intercalated compound Li₄Ti₅O₁₂ has been demonstrated to be one of the most promising electrode materials for such applications,because it has a flat voltage range,high reversible capacity (175 mA·g-1),and especially the long cycling performance due to no being a structural change zero-strain insertion material during charge-discharge cycling,besides these,titanium is inexpensive and existing abundantly in nature.However,the drawback of its poor electrical conductivity (10-13Scm-1) and low Li-ion diffuse coefficient(2×10-8cm2s-1) causes its poor rate capability.In order to advance the practical application of Li₄Ti₅O₁₂ and solve the problems of low electronic conductivity of lithium titanate, high energy consumption and low purity in the traditional solid state sintering, in the project, we use butyl titanate (Ti (OC4H9)4) and lithium acetate ( LiCH3COO?2H2O) as raw materials to synthesis nano-size Li₄Ti₅O₁₂ material by sol-gel method, and use citric acid as the carbon source for carbon coating to obtain Li₄Ti₅O₁₂/C composites, this is a improved material for conductive performance, and improved material high rate charge and discharge, not only enriching the content of Li₄Ti₅O₁₂ materials, but also promoting the practical application of Li₄Ti₅O₁₂ material in lithium ion batteries. The main results and conclusions obtained are as follows:1. Sol-gel method, by using P123 as surfactant, can synthesis good performance materials. The method adds acetic acid and P123 to control the reaction process. Well-dispersed and lower impurity phases nano-particles are obtained.2. Using citric acid as carbon source during the sol-gel method to carbon coat Li₄Ti₅0₁₂ particles, and to synthesize a composite material of Li₄Ti₅0₁₂/C. Studying the influence of the carbon content on the composite material structure and electrochemical performance. The results show that the increase in citric content is beneficial to improve charge-discharge rate performance. When the content of citric acid added in the sol-gel process is 2g, the rate performance of the product is best. The first discharge capacity is 161mA?g-1, the discharge retention efficiency is 85.4% at the current rate of 0.5C, and the discharge retention efficiency is 88.6% at the current rate of 5C.The sol-gel method by adding citric acid has improved the electronic conductivity of Li₄Ti₅0₁₂ and increased their charge and discharge rate performance. This is because using citric acid as carbon source and complexing agent can make the Li₄Ti₅0₁₂ particles more fine, well-distributed, and with high phase purity.