Synthesis And Modification Of Li₄Ti₅O₁₂ As Anode Material For High Performance Lithium-ion Battery

In this paper, Li4TisO12 (LTO) materials are synthesized by high temperature solid state and ionothermal methods. The influences of different ionic liquids, reaction time, temperature and carbon coating on the preparation of LTO morphology and electrochemical performance have investigated. The samples were characterized by powder X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy, N2 adsorption measurement, galvanostatic charge-discharge test and electrochemical impedance spectroscopy.The effects of synthetic methods, calcining temperature, coated carbon and other factors on the preparation and performance of the anode material were investigated. The results are as follows:TiO2 and LiOH as raw materials, after ball milling and heat treating at 800℃ with 8 h, the obtained sample which was synthesized via high temperature solid state method presents a uniform particle size around 600 nm. The capacity of LTO electrode are 157.2,131.5 and 104.4 mAh/g at 1C,10C and 20C, respectively. After 100 cycles, the discharge capacity retention of LTO remained 87.7% at 1C rate, indicating that the material has good cycle stability at low rate.The uniform nano LTO particles were obtained via ionothermal method by using Ti(OC4H9)4,CH3COOLi·2H2O as raw materials and three kinds of imidazolium-based ionic liquids:[EMIM]BF4, [BMIM]BF4 and [DEMIM]BF4 as solvents and structure-directing agents at ambient pressure. Ionic liquids play an important role in forming special morphology of LTO. The LTO synthesized using [DEMIM]BF4 exhibits sponge-like nanostructure.At 1 C rate, the initial discharge capacities of three LTO samples are 158.9,159.6 and 170.2 mAh/g, respectively. While at the rate of 20 C, the capacities are still 106.3,119.4 and 161.2 mAh/g. The sponge-like material also shows high-rate ability and cycling stability with the retention capacities of 95.1% and 91.0% at the rate of 1 C and 20 C after 100 cycles, respectively.Spinel structure materials of LTO/C were successfully synthesized by carbon coating. The composites are embedded in uniform carbon layer with about 3 nm thick. At 1 C rate, the initial discharge capacities of LTO/C-1 and LTO/C-2 are 157.2 and 172.2 mAh/g, while at the rate of 20 C, the capacities are still 104.4 and 161.2 mAh/g. The results show that carbon-coating further improves electrochemical performance of LTO with reduced charge transfer resistance and enhanced cycling stability.