Study On Synthesis And Modification Of Li₄Ti₅O₁₂ As Anode Material For Lithium Ion Battery With Sol-gel Method

Spinel Li4Ti5O12is a"Zero strain"electrode material, which has lots of favorable futures such as high safety, superior cycle performance, very flat charge and discharge voltage plateau, low cost and environment-friendly, is considered to be one of the most promising new anode materials for lithium ion batteries. However, low rate capacity and tap density of Li4Ti5O12affects the application performance, which limiting its commercial application. In this thesis, the current survey on lithium ion battery and anode materials, especially on the structure, properties, preparation methods and modification of spinel Li4Ti5O12material were introduced. Submicron and spherical Li4Ti5O12materials were synthetised by sol-gel method, and modified by doping V. TG-DSC, XRD, SEM, galvanostatic charge discharge, cyclic voltammogram etc have been employed to study the structure and electrochemical perporties of the obtained materials.Submicron Li4Ti5O12materials were synthesized by sol-gel method using adipic acid as complexing agent. The influence of sintering temperature, sintering time, adipic acid contents etc on the structure and electrochemical properties of materials were discussed. The results indicate the sample with the best structure and electrochemical properties was sintered at800℃for12h when the mole ratio of adipic acid and Ti(Ⅳ) is0.50. The sample shows high-purity cubic spinel Li4Ti5O12phase, with uniform particle distribution (150～300nm), almost without any agglomerates,and exhibits promising electrochemical properties. When charged at0.1C, the initial discharge specific capacity is169.59mAh/g, the charge capacity sustains158.17mAh/g beyond30cycles, and the capacity retention is93.4%.In order to improve the tap density of materials, spherical Li4Ti5O12materials were synthetised by sol-gel method using CTAB as structure directing agent. And the structure, morphology and electrochemical properties of the materials have been studied. The results show that the sample sintered at800℃for12h is cubic spinel Li4Ti5O12purity phase. Particles of the sample almost are spherical with excellent fluidity, uniform particle distribution, and exhibits excelent electrochemical properties. When charged at0.1C, the initial discharge specific capacity is160.25mAh/g, the charge capacity sustains146.52mAh/g after30cycles.Based on results of the first part, Li4Ti5-xVxO12(0<x<0.2) samples were prepared by sol-gel method. The influence of different vanadium contents on the structure and electrochemical performances of materials were investigated, and focus on the electrochemical performances of the obtained sample with optimum doping content. The results indicate doping a small amount of Vanadium almost not effect the basic spinel structure and Morphology characteristics of Li4Ti5O12. And V5+doped Li4Ti5O12lattice, which improved electronic conductivity of the material, improve the reversible capacity and cycle performance of the material.The obtained Li4Ti4.95V0.05O12sample exhibits excellent electrochemical properties. When charged at0.5C, the initial discharge specific capacity is155.76mAh/g/the charge capacity sustains151.26mAh/g beyond30cycles.