The Electrochemical Performance Of Lithium Titanate Composite Materials Research

Li₄Ti₅O₁₂ was produced by the direct molten-salt method in this paper. The compounds were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). It showed that the product prepared by heating a mixture of CH₃COOLi·2H₂O and TiO₂ powder at 70℃for 5h, subsequently calcined the pretreated mixture at 800℃for 2h was spinel structure with an average size of about 300nm with average distribution. The discharge capacity of the cathode was 147.5mAh·g^-1under 0.1C rate. After charged/discharged at 0.1C rate for 20 cycles, the sample retained a discharge specific capacity of 140 mAh·g^-1.Composite material was prepared to enhance the capacity of Li₄Ti₅O₁₂ by ball-milling method in this dissertation. Meanwhile, the composite effects were investigated by XRD, SEM, EIS, EDS and galvanostatic discharge-charge techniques.Based on the facts that Li₄Ti₅O₁₂ has very excellent cycling stability but very limited lithium-ion charge-discharge capacity, CO₃O₄ is employed to synthesize their composite by mechanical ball-milling to improve the applicability. Results showed that during the first cycle the anode delivers high discharge capacity value of 1290 mAh·g^-1 and remains a reversible charge capacity value of 371 mAh·g^-1 at 20^th cycle. Further more, the novel anode material shows a lower discharge potential plateau at 0.25 V, which was lower than both of Li₄Ti₅O₁₂ and CO3O4.Li₄Ti₅O₁₂/CoO compoite was obtained by milling a mixture of Li₄Ti₅O₁₂ and CoO. Scanning electron microscopy (SEM) and energy dispersive X-rays analysis (EDX) revealed that CoO were homogeneously distributed in the Li₄Ti₅O₁₂ matrix. The preliminary electrochemical test found that the Li₄Ti₅O₁₂/CoO composite exhibited an ultrahigh initial discharge capacity of 2605 mAh·g^-1 in the potential range of 3.0-0.01V and maintained 700 mAh·g^-1 after 20 cycles.The first intercalation of the spinel Li₄Ti₅O₁₂ electrode was studied using electrochemical impedance spectroscopy (EIS). Appropriate equivalent circuits were proposed to fit the experimental data. Based on the fitting results, the dependence of the resistance of SEI film, the resistance of charge transfer, the Warburg coefficient, the intercalation capacitance and the chemical diffusion coefficient on potential were obtained.