Study On Electrochemical Performances Of LiFePO₄ Cathode Material Prepared By Soft-Chemistry Routs

Olive-structured LiFePO₄ is a new kind of cathode material for lithium-ion battery. It has a relatively large theoretical capacity of 170mAh/g. This material is cheap and environmentally friendly, thermally stable in t he fully charged state. LiFePO₄ has a low electronic conductivity, and its cycle ability at large charge/discharged current should be improved. In this paper, LiFePO₄/C composite cathode materials have been synthesized. The micro-structures and morphologies of these materials were investigated by XRD, SEM, TEM observations. The electrochemical performances have been evaluated by galvanostatic charge-discharge and cyclic voltammetry (CV). The effects of the synthesis parameters on the physico-electrochemical properties of carbon-coated LiFePO₄ have been discussed in detail.The olive-type LiFePO₄ was synthesized via sintering the amorphous LiFePO₄ obtained by chemical reduction and lithiation of FePO₄, using VC as reducer and lithium acetate as lithium source in alcohol solution. The influences of sintering conditions on the physical and electrochemical properties of resulting LiFePO₄ were investigated. XRD patterns and SEM photos showed that increasing the sintering temperature and time leads to higher crystallinity, but to a larger particle size. The optimum sintering condition for LiFePO₄ with both small particle size at around 80nm and perfect crystal was determined, the LiFePO₄ sintered at 600℃for 2h exhibited better stability, and a stable discharge capacity of 159 mAh·g-1at 0.1C rate was reached.An HEDP-based soft-chemistry method for LiFePO₄ cathode material has been developed, using inexpensive HEDP as Fe3+ chelated agent and phosphonate source,...