Synthesis And Modification Of Nano Li₄Ti₅O₁₂ Materials For Li-ion Batteries

Li-ion batteries are widely used due to their excellent performance and broad market prospects in social life. Spinel LuTi5O12is a kind of "zero strain" anode material with excellent electrochemical properties, therefore it has become one of the hot pot in the Li-ion battery anode materials, and the critical issue of its practical application process is to improve Li4Ti5O12electrical conductivity and rate capability. Decreasing the materials’ resistance and polarization, as well as their electrode potential, improving the energy density of batteries could modify the electrochemical properties of the battery materials. This paper showed a facile synthesis process of nano Li4Ti2O12, and discussed the properties of the nano-Li4Ti5O12/graphene composite materials using The rmogravime try-differential thermoanalysis (TG-DTA), X-ray Diffraction (XRD), Scan electron microscope (SEM), Transmission electron microscopy (TEM). The materials’electrochemical properties were investigated by constant current charge-discharge test, AC impedance, Cycle Voltammagram (CV), to validate the best experimental conditions in order to promote the materials’ electrochemical performance.This study chose the orthogonal experiment method to disscuss the best experimental conditions for preparing nano Li4Ti5O12via "Sol-Gel" method. The final results showed that the optimum parameter was0.8:1in the raw materials rate of LiNO3and TiO2,700℃calcination temperature and4h calcination time. The average particle size of prepared Li4Ti5O12was200nm or so, and its initial discharge capacity reached to149.4mAh/g (0.5C) and the capacity retention rate remained in94.2%after100charge-discharge cycles under the0.5C magnification. The rate performance of Li4Ti5O12was excellent, the discharge capacity retention rate remained in87%after30cycles under0.1C,0.5C,1C rate (each ten cycles in turn).The "Hydrothermal" synthesis of nano-Li4Ti5O12/Grapheme was investigated and the best doping condition was studied according to the experiment results. Experimental results showed that the optimum parameter of the synthesis condition:2g nano Li4Ti5O12powders with25mg doped graphene, heated at130℃for60minites. The initial discharge capacity of the resulting material reached to165.7mAh/g (0.5C) and the capacity retention rate remained in95.7%after100charge-discharge cycles under the0.5C magnification. The rate performance of Li4Ti5O12was excellent, the discharge capacity retention rate remained in94.3%after20cycles under0.5C,1C rate (each ten cycles in turn).The "Hybrid" synthesis of nano-Li4Ti5O12/Graphene was investigated and the best doping condition was explored according to the experiment. Experimental results showed that the optimum parameter:2g nano Li4Ti5O12powders was doped with50mg graphene, followed by the calcining treatment at600℃for8h in the N2atmosphere. The initial discharge capacity of the resulting material reached to156.1mAh/g (0.5C) and the capacity retention rate remained in94.8%after100charge-discharge cycles under the0.5C magnification. The rate performance of Li4Ti5O12was excellent, the discharge capacity retention rate remained in89.6%after20cycles under0.5C,1C rate (each ten cycles in turn).Comparing three kinds of integrated materials, the initial discharge capacity of nano-Li4Ti5O12/Grapheme synthesized by the "Hydrothermal" method was improved by18.6%, and there was also15.0%rate performance improvement under the10C magnification. At the same time, the impedance was significantly reduced by28.6%.