Combustion Synthesis Of Li₄Ti₅O₁₂ And Electrochemical Performance Tests

While, for Li4Ti5O12, which had been used as anode materials for lithium ion batteries, there were almost no structure change during discharge and charge. We called it "Zero strain" material, that was why there was very small irreversible capacity lose. Li4Ti5O12 gave rise to many researchers and companies enough attentons, whch was due to its highlights, such as excellent electrochemical performances, environmentally friendly, low cost.In this paper, we worked over the preparation of spinel structure material Li4Ti5O12, which was prepared by solid state method, sol-gel method and hydrothermal method. We also studied the factors, which affected electrochemical performances, such as the calcining time, calcination temperature, molar ratio of lithium to titanium.The first one, we prepared the precursor by CH3COOLi·2H2O and amorphous TiO2. The studies manifested that with solid state method, the pure spinel structure material Li4Ti5O12 could be synthesized by calcinated the precursor at 800℃for 15h in the air in the muffle, and the first discharge specific capacity was 146mAh·g-1 at 0.1C, which was 83% of the theoretical capacity. The sample which was calcination by Microwave had better electrochemical performance, initial discharge specific capacity was 151mAh·g-1 at 0.1C. But it was not suitable for mass production. In order to increase the specific capacity of Li14Ti5O12, we coated sucrose solution of Li4Ti5O12, initial discharge specific capacity increased to 157mAh·g-1 at 0.1C. The addtion of carbon improved the conductivity of Li4Ti5O12.The second one, we synthesized Li4Ti5O12 by sol-gel method, discussed the conditions of the reaction. The gelation was good while the volume ratio of TiO(C4H9)4 and CH3CH2OH was 1:8, and the temperature of hydrolysis was 40℃. The precursor was analysed by TG-DSC, at the same time, we discussed the synthesis conditions by XRD, SEM, charge and discharge tests and cycle voltammogram tests. We founded that calcination time affected the purity of the products. The results showed that the spinel structure material Li4Ti5O12 could be synthesized at 800℃for 15h with TiO(C4H9)4 and CH3COOLi·2H2O as raw materials. The sample synthesized at 800℃for 15h had good crystal, unformly distributed, and initial discharge specific capacity was 155mAh·g-1 at 0.1C, But the discharge capacity was only 121mAh·g-1 at 1C, samples of the large charge and discharge performances were not satisfactory.The third one, we synthesized Li4Ti5O12 by hydrothermal method. At present, the hydrothermal method had been widely used to prepare cathode materials for lithium ion batteries, but few reported to prepare anode materials. It showed that the nanometer spinel material Li4Ti5O12 could be synthesized at 800℃for 15h with TiO(C4H9)4 and CH3COOLi·2H2O as raw materials. When the lithium was excessed 100%, initial discharge specific capacity was 160mAh·g-1 The last one, we also assembled Li4Ti5O12/LiCoO2 test battery, and the initial discharge specific capacity was 142mAh·g-1 at 0.1C.