The Synthesis And Characterization Of LifePO₄as A Cathode For Lithium Ion Batteries

Lithium iron phosphate (LiFePO4), with its olivine structure, has attracted extensive interest as a potential cathode material for lithium ion batteries because of its numerous appealing features, such as high theoretical capacity, good cycle stability, high safety, environmental benignity, and low cost. However, as a cathode material of lithium ion battery, the poor ionic conductivity and electrical conductivity of LiFePO4make its performance not be fully realized. In this work, we investigated a synthesis way to overcome the defects of LiFePO4in some extent as follows:1. We tried to control the particle size and uniformity of LiFePO4by adding different quantities of HEDP into raw materials in hydrothermal synthesis. and characterized particles synthesized by solid phase method and hydrothermal method without additives for comparison. The result suggested that LiFePO4grow in different direction, and have smaller particle size, good uniformity, good dispersion, when HEDP added in hydrothermal method.2. Carbon coating were conducted by ball milling or stirring of mixing LiFePO4and carbon source followed by carbonization at high temperature. The results indicated that LiFePO4/C obtained by stirring mixing maintaining better.3. Electrochemical tests indicated that when the smaller particle size of LiFePO4, the better electrochemical performance, through addition of HEDP as additive. When adding15%HEDP, the first charge capacity of LiFePO4material is154mAh/g, and the discharge capacity is140mAh/g (0.1C). After20cycles, the capacity is140mAh/g. When the charge and discharge rate was raised to2C, capacity declines is not obvious, with capacity of126mAh/g.