Development Of LiFePO₄ As New Type Cathode Material In Li-ion Batteries

Research on cathode materials in Li-ion batteries is developing towards high energy density, long cycle life, low cost and environment friendly. As a potential cathode material for Li-ion batteries, olivine-type lithium iron phosphate has been paid close attention in the past 10 years. It was inexpensive, non-toxic, environmentally benign, and it had high theoretical capacity (170mAh/g) and voltage (about 3.5V versus Li/Li+), good stability both at room temperature and high temperature, but it had low electronic conductivity and the reversible capacity loss at higher current dendity. Properties and research progress of LiFePO4 were summarized, with emphasis on the relation between its structure and properties, and the related research abroad for improving its properties including: (1) Preparation process of LiFePO4 (high temperature solid-phase process and low temperature liquid-phase process); (2) Modification with conductive materials to increase specific capacity at high current density. This paper applied high temperature solid-phase process to synthesis pure LiFePO4 and doped LiFePO4/C materials for lithium-ion battery, the crystalline structure, morphology of particles and crystalline size of the samples were investigated by X-ray diffraction and scanning electron microscopy. The results showed that LiFePO4 and LiFePO4/C were simple pure olive-type phase, and LiFePO4/C composite obtained with the glucose as carbon doped possessed excellent electrochemical performance. This paper summarized two possible models for lithium extraction/insertion within a given particle in the LiFePO4 system, modification with conductive materials to enhance specific capacity at high current density, method of preparation as well as the result concerned with enhancing its electronic conductivity of the field and the prospect of this new type cathode material in Li-ion batteries.