Abstract
Lithium iron phosphate (LiFePO4) has been a promising cathode material for Lithium ion batteries. Among the simplest, most widely studied and potentially most useful cathode material, much attention has been paid to it for its advantages, such as safety, environmental friendly, low material cost, high energy density, and very stable in common electrolyte systems. However, because of its lattice structure, it has extremely low electronic conductivity and very low lithium-ion diffusion coefficient, which has been the greatest obstacle for application of lithium iron phosphate. In 2002, researchers show that by super-valence ion doping,, it does enhance the capacity delivery at high discharge rate. So that super-valence ion doping is an effective method to improve the electrochemical property of LiFePO4. However, few further research results were reported, and there are still lots of problems that needed to be solved. In this paper, we first use sol-gel method to synthesize LiFePO4 and fine tune the synthesis process. Second we studied LiFePO4 based on Na+ doping. The result shows that the electrochemical performance after doping 1% Na+ doping at Li site is the same as 5% doping at Fe site. When using discharge rate at 4C, the capacity still maintain at 52% of discharge rate at 0.1C. There still need more researches to make improvement of electrochemical performance of LiFePO4.