Preparation And Electrochemical Properties Of Lithium Titanate Series As Anode Materials For Lithium Ion Batteries

This article mainly focuses on the research of lithium titanate(Li4Ti5O12) anode material for lithium ion battery. Overall, the optimum synthesis condition for Li4Ti5O12 was determined firstly, which prepared via a traditional solid-state method. Then, different methods were adopted to synthesize the Li4Ti5O12 anode material and a series of modification researches were also conducted. Additionally, other Ti-based material, such as Li2NiTi3O8 and LiVTiO4 were synthesized successfully via traditional solidstate method and sol-gel method, respectively. The Li2NiTi3O8 and LiVTiO4 were investigated as anode material for the first time, and their electrochemical characteristics were explored preliminary.The as-prepared Li4Ti5O12, Li2NiTi3O8 and LiVTiO4 materials were tested systematically by different physical and electrochemical methods. Electrochemical results indicated that the Li4Ti5O12 preheated at 400 oC for 4 h and then calcinated at 800 oC for 12 h shows the best electrochemical properties. On the basis of the above optimum, we further explored the “carbon washing”(post-calcination) effect on the electrochemical properties of Li4Ti5O12. The results showed that the particle size was increased slightly after the post-calcination, leading to an increase of the electrochemical impedance. The morphology analyses and N2 adsorption-desorption tests showed the increased pore size of the post-calcinated Li4Ti5O12 particles, which was beneficial for the Li-ion diffusion. And the AC impedance analysis indicated the higher Li-ion diffusion coefficient of the post-calcinated Li4Ti5O12. Constant current charge-discharge test demonstrated its high rate performance has been improved significantly, indicating that the "carbon washing"(post-calcination) process is an effective way to improve the electrochemical properties of Li4Ti5O12 anode material.Li2MoO4 modified Li4Ti5O12/C anode material has been synthesized by a ballmilling assisted rheological phase reaction method. The results show that the amorphous carbon is successfully coated on the surface of Li4Ti5O12 nanoparticles with partial doping of Mo6+ into the Li4Ti5O12 structure. Electrochemical results indicate that the 5 wt.% Li2MoO4 modified Li4Ti5O12/C samples deliver the optimal rate capability and decreased charge transfer resistance.In situ nickel/carbon coated Li4Ti5O12 has been synthesized successfully via a facile sol-gel method with chitosan serving as chelating agent and carbon source. The asprepared Li4Ti5O12@Ni/C composite shows excellent rate capability and cycling stability. The remarkable improvement of the electrochemical properties should be attributed to the Ni/C coating layer, which inhibits the growth of crystal grains, also acts as an effective conductor and a protective material against side reactions with electrolyte.In addition, the Li2NiTi3O8 and LiVTiO4/C composite were prepared via solid-state method and sol-gel method, respectively. The Li2NiTi3O8 and LiVTiO4/C were investigated as the anode materials for the first time and their electrochemical properties were studied preliminary. The Li2NiTi3O8 and LiVTiO4/C both showed considerable reversible capacity in the cut-off voltage of 0.02~3.0 V, indicating they all have a certain of research value.