Synthesis And Electrochemical Properties Of Li₄Ti₅O₁₂ As Anode Material For Lithium-ion Batteries

Lithium-ion battery has been considered as one of the most promising green secondary batteries due to its excellent properties such as high working voltage, long cycling life, high specific energy, non-memory effect, and non-pollution. The spinel Lithium Titanate (Li4Ti5O12) is a "zero-strain" material because it has high stability and excellent cycling performance due to no structural change in the process of charging and discharging, besides, owing to its advantages of high stability, good cycle performance, good safety performance, low price, non-pollution, Li4Ti5O12 has great potential for development of lithium-ion battery cathode material.The preparation of Li4Ti5O12 needed high synthesis temperature, long synthesis time by traditional high-temperature solid-phase method, and the product had poor charge-discharge performance and cycle performance. In this paper, the spinel Li4Ti5O12 was synthesized with Li2CO3 and amorphous TiO2 as starting materials at lower milling temperature and shorter milling time by high temperature mechano-chemical method, which would promote the industrial application of Li4Ti5O12 material.The paper investigated the process conditions of preparation of Li4Ti5O12 materials which affected the physical and electrochemical properties of Li4Ti5O12 materials by high temperature mechano-chemical method:n(Li)/n(Ti), milling temperature, milling time, ball-to-powder weight ratio, ultrasonic dispersing and mechanical stirring pretreatment for starting materials. The physical performance of the materials were characterized by Scanning electron microscopy (SEM), BET specific surface area, Laser particle analysis; and the crystal structure and electrochemical performance of the materials which were affected by conditions of action and pretreatment processes were investigated by X-ray diffraction (XRD), Thermogravimetry-differential thermoanalysis (TG-DTA), AC impedance, Cycle Voltammagram (CV), charge-discharge tests.The research showed that spinel Li4Ti5O12 material was synthesized at 750℃ for 3.5 hours with Li2CO3 and amorphous TiO2 as starting materials with the ball-to-powder weight ratio of 8:1 and n(Li)/n(Ti)=0.82 by high temperature mechano-chemical method. The discharge specific capacity was 161.155mAh/g after first cycle at 0.1C, and almost without attenuation after 15 cycles. When Li2CO3 and amorphous TiO2 were pre-processed by ultrasonic dispersing for 1 hour, the discharge specific capacity was 175.904mAh/g after first cycle at 0.1C, and the discharge capacity retention was above 96.25% after 14 cycles. Even more, Li2CO3 and amorphous TiO2 were pre-processed by mechanical stirring for 2 hours, the discharge specific capacity was 179.270mAh/g after first cycle at 0.1C, and the discharge capacity retention was above 95.67% after 14 cycles. Both pretreatment processes greatly improved the electrochemical performance of Li4Ti5O12 material.