Preparation Of Dy-doped Li₄Ti₅O₁₂ And Its Electrochemical Performance Investigation

With the continuous innovation of modern science and technology, people’s requirement of safety performance of lithium ion battery is higher and higher, the traditional commercial lithium ion batteries are mostly do the cathode of carbon mat erials, but low carbon negative electrode potential close to lithium metal, so large current charging conditions on the surface of carbon anode materials are easy to generate "dendritic", causing security problems.This paper studied on the preparation and the method to improve properties of anode materials Li₄Ti₅O₁₂. The structure of the Li₄Ti₅O₁₂ material was investigated by X-ray diffraction（XRD）, Fourier transform infrared spectroscopy（FTIR）,scanning electron microscope（SEM）, and the electrochemical performance was mainly studied by using cyclic voltammetry（CV）, electrochemical impedance spectroscopy（EIS） and charge-discharge tests.The main experiments as follows:1.A sol-gel method assisted high temperature solid state reaction has been successfully employed to synthesize spinel Li₄Ti₅O₁₂ anode materials. In this work, the effect of Li:Ti atomic ratio was systematically investigated. The structure of the Li₄Ti₅O₁₂ material was investigated by X-ray diffraction（XRD）, scanning electron microscope（SEM）, and the electrochemical performance was mainly studied by using cyclic voltammetry（CV）, electrochemical impedance spectroscopy（EIS） and charge-discharge tests. Results of electrochemical measurements demonstrated that when the atomic ratio of Li to Ti was 0.8:1, the best electrochemical performance was exhibited by the composite, delivering an initial discharge capacity of 160 mAh g-1 at 0.2 C and maintaining 78.1% of its initial capacity after 20 cycles.2.For the first time, Dy（Dysprosium）-doped lithium titanate was prepared by a sol-gel method assisted high temperature solid-state reaction, and the influence of Dy content on the electrochemical performance of LTO was thoroughly examined. The structure and morphology of the as-synthesized materials were mainly examined by X-ray diffraction（XRD） and scanning electron microscopy（SEM）, and the electrochemical performance of the prepared samples was studied using cyclic voltammometry（CV）, galvanostatic charge-discharge tests and electrochemical impedance spectroscopy（EIS） measurements. The obtained XRD patterns strongly not only demonstrated the formation of crystalline Li₄Ti₅O₁₂, but also proved that the doped Dy could lead to the formation of Li2Ti4O9. SEM images indicated that when the atomic ratio of Dy to Ti was 0.06:4.44, some irregular smaller particles were found to be anchored on the surface of some huge particles. The results of electrochemical measurements revealed that Li4Ti4.44Dy0.6O12 sample exhibited a specific capacity of 145 mAh g-1 after 20 cycles at a current rate of 0.5 C, which was much larger than that of Li₄Ti₅O₁₂（104 mAh g-1） and Li4Ti4.8Dy0.2O12（101 mAh g-1）.3.A sol-gel method assisted high temperature solid state reaction has been successfully employed to synthesize spinel Li₄Ti₅O₁₂/SnCl₄ composites. In this work, the effect of Ti:Sn atomic ratio was systematically investigated. The structure of the Li₄Ti₅O₁₂/SnCl₄ material was investigated by X-ray diffraction（XRD）, scanning electron microscope（SEM）, and the electrochemical performance was mainly studied by using cyclic voltammetry（CV）, electrochemical impedance spectroscopy（EIS） and charge-discharge tests. Results of electrochemical measurements demonstrated that when the atomic ratio of Ti to Sn was 4.6:0.4, the best electrochemical performance was exhibited by the composite, delivering an initial discharge capacity of 194 mAh g-1 at 0.2 C and maintaining 81.1% of its initial capacity after 20 cycles, which was remarkably superior to the pure Li₄Ti₅O₁₂ that was prepared by the same process in the absence of SnCl₄.4.A high temperature solid state reaction has been successfully employed to synthesize different types of lithium ferrite. In this work, the effect of Fe:Ti atomic ratio was systematically investigated. The structure of the lithium ferrite was investigated by X-ray diffraction（XRD）, scanning electron microscope（SEM）, and the electrochemical performance was mainly studied by using cyclic voltammetry（CV）, electrochemical impedance spectroscopy（EIS） and charge-discharge tests. Results of electrochemical measurements demonstrated that when the atomic ratio of Fe to Ti was 8:1, the best electrochemical performance was exhibited by the composite, delivering an initial discharge capacity of 760.7 mAh g-1 at 100mAg-1 and maintaining 55% of its initial capacity after 20 cycles.