Studies On The Synthesis And Electrochemical Performance Of Modified Li₄Ti₅O₁₂ As Anode Materials For Lithium-ion Battery

The spinel lithium titanate due to its effect of “zero strain”, the outstanding of the higher lithium electricity discharge platform attract many researchers. Using the Sol-Gel method combined with the Chemical Deposition method to prepared corresponding anode materials was presented in this paper. The physicochemical properties of the has been prepared active materials were extensively measured by powder X-ray diffraction(XRD), Scanning electron microscope(SEM), Electrochemical performance test.Anode material Li4Ti5O12 was triumphantly sythetized by mean of the Sol-Gel method followed by sintering using tetrabutyl titanate( Ti(OC4H9)4), lithium carbonate(Li2CO3) and oxalic acid( C2H2O4) serve for staring materials. In the condition of determining the calcining temperature and the calcining time, effect on the performance of anode materials of the lithium titanium mole ratio was studied. The experimental result showed that the best ratio of lithium titanium mole was n(Li)/n(Ti)=0.85(the sample of 6%). The voltage range of test was between 1.0-3.0V. The galvanostatic discharge-charge testing indicated that the phase-pure Li4Ti5O12 material shows an initial charge specific capacity of 128.13 m Ah/g at 1C rate, and the initial discharge specific capacity was 120.39 m Ah/g. Combining the Sol-Gel method with the chemical deposition method to prepared the composite active materials Li4Ti5O12/Sn O2,and the best quality percentage of Sn O2 was studied. The quality percentage of 5% was showed the excellent electrochemical performance after the explore experiments. Though coated the right amount of Sn O2 on the surface of pristine material cannot appear to change the basic lithium titanate structure, the size of the particles were grew up. The galvanostatic discharge-charge testing showed that the first discharge specific capacity of composite materials Li4Ti5O12/Sn O2 was 178.21 m Ah/g at 0.1C rate, but the cycle performance under different rates remained to be improved in the further.In order to improve the ionic conductivity of Li4Ti5O12 active material, Cu-doped Li4Ti5O12 anode materia with Cu SO4?5H2O was used as copper source in the form of Li4Ti5-x Cux O12(0≤x≤0.30) were preparation successfully by the method of Sol-Gel. The results indicated that, the amount of copper was x=0.25 showed the optimal electrochemical performance, at the same time, the structure of lithium titanate did not changed after doped copper ions, and the sizes of particle obviously shrunk down to 200nm; Not only enhanced the specific capacity of the pure Li4Ti5O12 active materials, but also showed the great rate performance under the different rates. For further improve the electrochenmical properties of anode materials, Cu-dope Li4Ti5O12/Sn O2 composite anode materials in the form of Li4Ti4.75Cu0.25O12/Sn O2 was synthesized via the Sol-Gel method and the chemical deposition method; Systematic explores the cooperation affect of the Cu-doping and Sn O2-coating to the electrochemical properties of Li4Ti5O12 active materials. The experimental results found that Li4Ti4.75Cu0.25O12/Sn O2 composite material can improve the rate capability, the cycle performance got guarantee in the meantime as well. Under a potential of 1.0-3.0V, the initialspecific discharge capacity was 202.55 m Ah/g at 1C, and 202.51 m Ah/g about over 50 cycles,only 0.02% of capacity loss occurs to the composite active materials.