Preparation And Modification Of Spinel Lithium Titanate As Anode Materials For Li-ion Battery

Spinel Li₄Ti₅O₁₂2 has attracted more and more attention because of its nickname as"zero strain"material,high lithium insertion potential?1.55V vs.Li/Li⁺?and stable crystal structure during charge and discharge.However,the Li₄Ti₅O₁₂2 anode material has defects such as low ionic conductivity,which limits its application.In this paper,Li₄Ti₅O₁₂2 anode materials were synthesized by sol-gel method using lithium acetate,butyl titanate and citric acid as raw materials,and modified by ion doping and surface coating.The structure and electrochemical properties were studied by X-ray diffraction?XRD?,scanning electron microscopy?SEM?,constant current charge and discharge measuring.The results show:1)When the molar ratio of lithium to titanium is equal to 0.8 and the lithium acetate content is increased to 3 wt%,the electrochemical performance of Li₄Ti₅O₁₂athode material is the best.The first discharge specific capacity is 133.0 mAh/g at 1 C rate and the discharge platform is 1.5 V.The retention rate was stable after 50 cycles,the first time is 133.0 mAh/g,and the last time is 129.35 mAh/g.The capacity retention rate was 97.26%.2)The Zn²⁺was doped in the lithium and titanium sites to prepare the Li_3.93Zn_0.10Ti_4.97O₁₂2 anode material,and the surface was coated with NiO to investigate the different coating amount on the Li_3.93Zn_0.10Ti_4.97O₁₂/NiO anode effect to the electrochemical properties.The results show that the electrochemical performance of the 5%NiO coated sample is the best.The sample coated with 5%NiO has high crystallinity,good crystal form,uniform distribution and small particle size.The first discharge specific capacity is 174.3 mAh/g at 1 C rate,and the first discharge specific capacity after stabilization is 156.6 mAh/g.After 50 cycles,the specific capacity of the discharge was 147.2 mAh/g.The specific capacity of the sample coated with 5%NiO was higher,but the stability was slightly worse than that of the pure phase,which needs to be improved.3)Li₄Ti_5-xCu_xO₁₂2 anode material was prepared by doping Cu²⁺at the titanium site by sol-gel method.The surface of La₂O₃ was coated with La₂O₃ to investigate the effect of different coating amount on the electrochemical properties of Li₄Ti_4.75Cu_0.25O₁₂/La₂O₃ anode materials,and the optimum coating amount of La₂O₃was explored.The results show that the electrochemical performance of the sample coated with 15%La₂O₃ is the best.At 1 C rate,the specific discharge capacity of 15%La₂O₃ was 162 mAh/g,and after 50 cycles,the specific discharge capacity was 155mAh/g,and the stability was good.At different rates of charge and discharge and the discharge platform is about 1.55 V,the discharge specific capacity at 0.1 C rate is193.2 mAh/g,which is higher than other rates.