Research On Doping And Modification Of Olinie Phosphate Iron Lithium Cathode Material

The increasing concerns on energy, environmental and the rapid development of modern science and technology have more demands on batteries. Lithium ion batteries (LIB) are attractive for use in the field of mobile power source with the favorable properties of high voltage, long cycling life, high energy density, non-memory effect and pollution-free. Intensive research is being conducted to further improve the performance of lithium ion batteries and reduce the cost of electrode materials. Because of its high theoretical capacity (170 mAh·g^-1), and feasible voltage (about 3.5V versus Li⁺/Li), good stability both at room temperature and high temperature, and being environmental benign and inexpensive, LiFePO4 is very hopeful material as positive electrode materials for the future lithium-ion batteries material. However, inhering limit from that in the layered and spinel structures, there is no continuous network of FeO₆ edge-shared octahedral that might contribute to electronic conductivity, resulting in a extremely low electronic conductivity, which has been the greatest obstacle for application of lithium ion phosphate. When current density increases, its reversible capacity drops dramatically.On the base of reviewing the development of lithium ion battery and its cathode materials in detail, olivine LiFePO₄ were chosen as cathode material and their synthesis and modification were studied. In this paper LiFePO₄ powders were prepared via solid-state reactions mehtod that involve multiple steps at high temperatures. The effects of synthesis conditions on structure and electrochemical behavior of LiFePO₄ were studied. Meanwhile the modified materials were also conducted on the basis of LiFePO4 material. In addition, we used X-Ray Diffraction (XRD) to analyze phase composition, Scanning Electron Microscope (SEM) to observe superficial morphology, charge-discharge test to study specific capacity and cyclic properties, Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscope (EIS) to discuss electrochemical reactive mechanism.The study show that doped-LiFePO4 have an good olivine structure and good electrochemicval using LiF as Li source via high solid-state reaction...