Preparation And Electrochemical Performance Study Of Li₄Ti₅O₁₂ With High Safety Using As The Anode Materials For Lithium Battery

Recently, Li₄Ti₅O₁₂ has attracted great attention as anode material for lithium-ion batteries for electric and hybrid vehicles. Li₄Ti₅O₁₂ inherently has several advantages: 1) zero-strain, i.e., no volume change during lithium intercalation/deintercalation; 2) high operating voltage-plateau to minimize the decomposition of liquid electrolyte and the formation of solid electrolyte interface?SEI? films. However, the main disadvantages of Li₄Ti₅O₁₂ are its low Li+ diffusion coefficient and poor electronic conductivity, which limit the use of Li₄Ti₅O₁₂ anodes in practical lithium-ion batteries. To improve the conductivities, three effective ways have been tried, including doping with metal ions, incorporation of the second phase with high conductivity, and particle size controlling method.Firstly, Li₄Ti₅O₁₂ and Mg&Zr-doped Li₄Ti₅O₁₂ with the formulation of Li3.8Mg0.2Ti4.8Zr0.2O12 were prepared by a modified solid-state method. The structure and electrochemical properties of the as-prepared powders were systematically investigated. Li3.8Mg0.2Ti4.8Zr0.2O12 exhibited an excellent rate capability with a discharge capacity of 169.6 mAhg-1 at 1 C, 144.2 mAhg-1 at 2 C, 113.1 mAhg-1 at 5 C,which were better than that of the pure Li₄Ti₅O₁₂. Electrochemical impedance spectra?EIS? revealed that the Li3.8Mg0.2Ti4.8Zr0.2O12 exhibited the improved electronic conductivity than that of Li₄Ti₅O₁₂. The novel Li3.8Mg0.2Ti4.8Zr0.2O12 material stands as a promising potentially high rate anode material for the lithium ion batteries.Second, Li₄Ti₅O₁₂ and Li₄Ti₅O₁₂/C fibers were synthesized through the electrospinning method. It was found that both fibers show higher reversible capacities and better rate performance. Comparing the two electrospun samples, Li₄Ti₅O₁₂/C fibers exhibit higher reversible capacity, greater rate capacity, and smaller electrode polarization, indicating that Li₄Ti₅O₁₂/C fibers have higher conductivity than Li₄Ti₅O₁₂ fibers due to the elimination of Li₄Ti₅O₁₂ aggregates and the formation of carbon-based fiber structure. Electrochemical impedance spectra?EIS? revealed that the Li₄Ti₅O₁₂/C exhibited the improved electronic conductivity than that of Li₄Ti₅O₁₂.Last,the pure Li₄Ti₅O₁₂ material was synthesized by the hydrothermal method. The influence of the sintering temperature on the electrochemical performance for Li₄Ti₅O₁₂ was studied. It was found that Li₄Ti₅O₁₂ sintered at 750? showed better C-rate performance than that of the other two samples sintered at 700 and 800?, respectively. Moreover, the sample sintered at 750? possessed a much better capacity retention of 89% after 50 cycles. Li₄Ti₅O₁₂ materials sintered at 750?showed the discharge capacity of 235mAhg-1 at a charge–discharge C-rate of 0.5C for the first cycle, which was 34% higher than the theoretical capacity. It could probably be due to the contribution of the carbon capacity left in the sample.