Study Of LiFePO₄ As Cathode Material For Lithium-Ion Battery

The increasing concerns on energy, environmental and the rapid development of modern science and technology have more demands on batteries. Lithium ion batteries (LIB) are attractive for use in the field of mobile power source with the favorable properties of high voltage, long cycling life, high energy density, non-memory effect and pollution-free. Intensive research is being conducted to further improve the performance of lithium ion batteries and reduce the cost of electrode materials. On the base of reviewing the development of lithium ion battery and its cathode materials in detail, olivine LiFePO4 were chosen as cathode material and their synthesis and modification were studied.Precursor Li3PO4·1/2H2O and Fe3(PO4)2·8H2O were prepared by codeposition method. The powder was very small(about 10μm) and mixed well. The pure active material can be sintered in 5 hours by using solid-state method. The particles'diameter is smaller than that which be sintered by u sing common raw material. Cycle ability was improved. The additive of VC can restrain oxidation. The precursor can be free of drying by using acetone.Olivine LiFePO4 was synthesized by microwave heating and the reactions could be finished within few minutes. Some special techniques can prohibit oxidation, such as adding addition and adopting two-step way. The effects of sinter conditions on physical performance and electrochemical behavior of olivine LiFePO4 were studied. And we made certain the best sinter condition. The results showed the samples by microwave heating exhibited smaller particles, high specific capacity (129 mAh·g-1).LiFePO4 was sintered by solid-state method, we found that the capacity of the sample which was synthesized by codeposition method exhibited high specific capacity(142 mAh·g-1) and good cycling performance. But electrochemical reaction is more difficult than that was sintered by microwave heating.