Research On Li₄Ti₅O₁₂ And Its Composite Anode Materials For Lithium-ion Batteries

Li4Ti5O12spinel anode material is very promising for electrodes in a large number of battery applications for it exhibit no structural change (zero-strain insertion material) and have good Li-ion intercalation and de-intercalation reversibility during charge-discharge cycling.This passage reviewed the research progress of Li4Ti5O12spinel anode material.Citric acid sol-gel synthesis method was primarily used in this paper,so as to enhance the electrochemical properties by reducing particle size and surface modification.Detailed work were done as follows:Using CH3COOLi,C16H36O4Ti as raw materials,citric acid as complexing agent,the Li4Ti5O12was synthesized by citric acid sol-gel synthesis method.Effect of different calcining time on the Li4Ti5O12material at the same calcining temperature (800℃)was systematically investigated by TG-DTA,X-ray diffraction (XRD),scanning electron microscopy (SEM),galvanostatic charge-discharge test and cyclic voltammetery(CV).The results show that the good properties of Li4Ti5O12can be prepared by citric acid sol-gel synthesis method with heating at800℃for12h.The as-prepared sample was well-distributed with a narrow size distribution from100to200nm,and it showed the best electrochemical properties.On the bases of the study on preparing the pure samples by using citric acid sol-gel method, a series of Li4Ti5O12/NiO composite materials were fabricated by chemical deposition combined with thermal decomposition of a mixture of Li4Ti5O12,Ni(NO3)2·6H2O and NH4HCO3. Li4Ti5O12/NiO composite materials structure,morphology and electrochemical properties were systematically investigated. The Li4Ti5O12/NiO(5%) presents the best performance among all the samples, proper coating can efficiently improve the electrochemical performance of Li4Ti5O12.The discharge capacity of Li4Ti5O12/NiO(5%) was228.3mAh/g at the discharge/charge current density of30mA/g and the voltage range of2.5～0.1V after30cycles,which is23.8mAh/g higher than the pristine Li4Ti5O12.CV test proved that NiO did not inhibit the migration of lithium ions during the electrode reaction of Li4Ti5O12/NiO(5%) composite,meanwhile it increased the conductivity and decreased the electrode polarization of Li4Ti5O12.A advanced pechini method is provided to prepare Li4Ti5O12/C composite with different carbon content. In this technique,Li4Ti5O12/C composite was obtained by calcination of a citrate precursor in N2at a high temperature, followed by annealing in air at a low temperature.The physical and electrochemical properties of the obtained samples have been studied by XRD,SEM,TEM,TG-DSC,cyclic voltammetery(CV) and galvanostatic charge-discharge tests.The results demonstrated that the crystallization,microstructure and electrochemical performance were influenced significantly by carbon from the pyrolysis of citric acid and the annealing process at a low temperature.The Li4Ti5O12/C composite with carbon coating of4.6wt%after annealed at a low temperature exhibited the best electrochemical performance.Compared with its capacity at1C rate,the corresponding capacity retention at5C and IOC rate were86.6%and64.8%after30cycles,respectively indicating the good cycling and rate performance.