Studies On Synthesis And Property Of Lithium Vanadium Oxides As Cathode Materials For Lithium Ion Batteries

Rapid progresses have been made in the research on lithium ion batteries due to its superior properties for recent years. These properties, however, are greatly affected by the selection and preparation of the materials, such as the electrode materials, the electrolytes and the separators, particularly the cathode materials. The research on cathode materials is focused on layered compounds LixMO₂ and spinel compounds LixM₂O₄ (M=Co,Ni,Mn,V and other transition metal ions). The shortage of the cobalt resources results in the high price of LixCoO₂ as cathode material. The cathode material of LixNiO₂ with perfect crystal structure is very difficult to be prepared. The capacity of LixMn₂O₄ falls down rapidly with time in practice. If the factors of low price, no contaminate, high capacity and comprehensive electrochemical are considered, the cathode material of lithium vanadium oxides should be recognized as the most potential cathode materials for lithium ion batteries.At present, the lithium vanadium oxides mostly are LixVO₂,LixV₂O₄,Li6V5O15,Li1+xV3O8 and LiNiVO4, they have comprehensive electrochemical properties. There also some new lithium vanadium oxides have appeared, such as LiVPO4F,LiVP2O7,Li3V2(PO)3 and VOPO4. Nanomaterials have performed some extraordinary behaviors, such as electrochemical, crystal structure, morphology and physical property.In this paper, the preparing technological parameters, formation mechanism and structures of lithium vanadium oxides (nano LiV3O8, spinel LiNiVO4 and LiCoVO4, and doping transition metal ions in LiV3O8) are systematically studied and discussed, and some properties of the products are measured as cathode materials for lithium ion batteries. The main results are as follow:(1) Low-heating solid state method has been used to prepare nanomaterials LiV3O8. We discussed the influence of synthesis condition to the purity and structure, analysis the form mechanism of the production, and the preparation parameters are optimized. Compared to sol-gel method, the temperature has cut down to 3000C, and the time to 6h. Compared to other wet method, the preparation parameters is easy, the production is integrity structure,pure and have comprehensive electrochemical properties.(2) LiV3O8 has been successfully synthesized by an inorganic sol-gel method. Doping transition metal ions(Mn,Ti,Co,Ni) to improve its electrochemical.(3) LiV3O8 have been synthesized by hydrothermal method. And we analysis the affect of morphology and physical property for different raw materials and different synthesis temperature.(4) LiV3O8 mesoporous-nanorods were synthesized by low heating solid state method in which PANI was used to modification LiV3O8 to synthesize a precursor. The production implies comprehensive electrochemical properties.