Preparation And Modification Of Li₄Ti₅O₁₂ As Anode Material For Lithium-ion Battery

With light weight and high power density, Lithium-ion battery has become one of the most promising new energy materials. Li+ insertion voltage of traditional carbon as anode material is almost close to OV. Lithium dendrites will grow on the surface of carbon electrode during high current or over-charged, which is easy to form a short circuit and results in safety issues. Spinel Li4Ti5O12 is considered to be an alternative to carbon as newly anode material for lithium-ion battery. The structure remains stable during fast charge-discharge of Li+ dein-tercalation repeatly that can improve the safety and stability performance. However,Li4Ti5O12 has an insulation character which results in low elctrochemical performance. In this work, we studied deeply in the preparation process, dophant and surface modification of Li4Ti5O12. The effects of dophant on structure, morphology, cycling performance and electronic prosperity were investigated.In the project, Spinel Li4Ti5O12 was preparated by the molten salt method with mixed phases of anatase and rutile TiO2 for the first time and low melting point CH3COOLi·2H2O as precursors. The effects of calcination temperature and reaction time on structure, capacity and cycling performance were investigated. Experiment results indicated that the sample show the best electrochemical performance as the precursors being heated at 70℃for 5h and subsequently sintered at 800℃for 5 h at a rate of 10℃per minute for heating process. The pure phase Li4Ti5O12 had a higer reversible capacity and excellent cycling performance. Compared with the traditional solid state method, melten salt method is less demanding on the titanium source, shorter heating time and lower temperature on sythesis of spinel Li4Ti5O12.Various dopants were preparated via the molten salt method. Na ions were doped availably. The research indicated that the substitute with x=0.08 of Na-doped Li4_xNaxTi5O12 (x=0,0.02,0.04,0.08,0.1) performed the best cycling and electric conduction performance. In this paper, we also doped or coated Li4Ti5O12 with La(NO3)3 or AgNO3 as raw materials. Useful research has been investigated on structure and electrochemical performance of Li4Ti5O12/La and Li4Ti5O12/Ag. It suggested that the sample of Ag/Ti with a ratio of 1:100 exhibited a better rate property than pure phase Li4Ti5O12.In this work, L14T15O12 with hige density was prepared by sol-gel method. Na+ and La3+ were both doped in Li4Ti5O12. The product of Li4-xNaxTi5O12/La (n(La/Ti)=1:100,x=0.05) has a higer electrochemical performance.