Investigation On Preparation And Performance Of Li₄ti₅o₁₂

Lithium titanate as lithium-ion battery anode material was prepared by solid-state method using TiO2-anatase and Li2CO3 as raw materials, which were mixed by stoichiometric amount. The spinel Li₄Ti₅O₁₂ material was synthesized under N2 atmosphere. The microstructure and morphology of the samples were characterized by XRD, SEM and LPS. The electrochemical performance was evaluated by galvanostatic charge-discharge cycling in the voltage range of 1.0².5V (vs. Li/Li+).The basic synthesis conditions of pure Li₄Ti₅O₁₂ were determined by orthogonal experiments L9(33), and the influence of synthesis temperature, synthesis time and n(Li)/n(Ti) ratio on the structure and electrochemical performance of Li₄Ti₅O₁₂ was investigated. The obtained synthesis conditions were as follows: raw materials were mixed by n(Li)/n(Ti)=0.84, first held at 600℃for 4h, and then calcined at 850℃for 4h. The experimental results showed that the as-prepared samples had cubic spinel crystal structure, consistent with standard Li₄Ti₅O₁₂ card. The samples showed a high crystallinity, and homogeneous particle size distribution with an average particle size of 0.87μm. The obtained Li₄Ti₅O₁₂ sample exhibited optimal electrochemical performance with an initial specific discharge capacity of 181.9mAh/g at 0.2C rate, whose discharge capacity could still reach 131.9mAh/g after 50 cycles at 1C rate with excellent cycling performance.Li₄Ti₅O₁₂/C material was synthesized by adding organic carbon sources, which increased the electronic conductivity to 10-3S/cm. The influence of different carbon sources and amounts on the crystal structure, particle size distribution and electrochemical performance of Li₄Ti₅O₁₂/C was studied. Among which, Li₄Ti₅O₁₂/C prepared with glucose as carbon source and a carbon amount of 2% was suitable for high-rate discharging. In addition, the prepared Li₄Ti₅O₁₂/C showed better electrochemical performance and stability with an initial specific discharge capacity of 190.8mAh/g at 0.2C rate, whose specific capacity was as high as 151mAh/g after 80 cycles at 1C rate with a cycling capacity retention rate of 94.85%.Nano-sized Li₄Ti₅O₁₂/C composite was synthesized by sol-gel method using CH3COOLi·2H2O and Ti(OC4H9)4 as raw materials, oxalic acid as chelating agent and carbon source. The effect of lithium source amount and sugar addition on the mirostructure and electrochemical properties of the as-prepared composites was systematically investigated in this paper. The results showed that Li₄Ti₅O₁₂/C composite with 5% excess of lithium source calcined at 750℃for 8h under N2 atmosphere, exhibited a phase-pure spinel structure and much smaller particle size. It delivered initial discharge capacities of 182.5, 162.7, 155.7 and 155.3mAh/g at 0.2, 1, 2 and 5C rates, respectively, which could still reach 153.9mAh/g after 50 cycles at 5C rate with a cycling capacity retention rate of 98.4%. SEM analysis indicated that the as-prepared Li₄Ti₅O₁₂/C composite using sucrose as an additional carbon source showed a spongy nano-particle aggregate structure, with an average nano-particle size of 80¹00nm, which was more advantageous to the fast lithium-ion insertion and extraction. The electrochemical results showed that the Li₄Ti₅O₁₂/C composite prepared in the presence of sucrose exhibited better electrochemical performance with a specific discharge capacity of 154.6mAh/g at 5C rate, and an improved tap density of 1.48g/cm3.