Synthesis Of Cathode Materials Of LiFePO₄for Li-ion Batteries By Hydrothermal Method

The increasing concerns on energy, environmental and the rapid development ofscience and technology have more demands on batteries. Lithium ion batteries areattractive for use in the field of mobile power source with the favorable properties ofhigh voltage, small self-discharge, non-memory effect and pollution-free. As the mostpromising cathode material of lithium-ion battery, the olive LiFePO4has lots ofadvantages, such as low cost, large theoretical capacity, long cycle life, goodthermostability, no memory effect and so on. However, due to the restrictions of theolivine structure, its electronic conductivity and lithium ion diffusivity are low,resulting in low specific capacity and bad C-rate performance. There are three ways toovercome these defaults: reducing the size of particles, doping and surfacemodification.This paper prepared nanosized LiFePO4/C by hydrothermal method. Wedetermined the best technologcial condition through the quest and orthogonal test.The LiFePO4/C was characterized by XRD, SEM, TG analysis. The electrochemicalproperties of the samples was tested by Land CT2001A. The results indicated that thesample synthesized at the best technological condition displayed goodelectrochemical property. The first discharge capacity was158mAh/g at0.1C.This paper also prepared LiFePO4/C samples by surfactant-assisted hydrothermalmethod. The results indicated that this method can control the morphology andparticle size significantly. The results of TEM, Raman and fluorescence analysisindicated that non-ionic surfactant (PVP) can modulate the carbon coating layers.At last, this paper researched the effects of cationic and anionic surfactants onthe performance of LiFePO4/C materials. The results indicated that the cationicsurfactant can reduce the particle size and make them well distributed. The samplesprepared at present of cationic surfactant have good electrochemical performance,especially high-rate performance. This synthesis method extended the application ofnanotechnology in synthesizing electrode materials.