Preparation And Electrochemical Characterization Of LiFePO₄/Cu As Cathode Materials In Lithium Ion Batteries

Lithium-ion battery is a very promising energy storage device. It has been widely used in mobile phones, laptop computers, cameras and other portable electronic devices. And the growing field of electric vehicles will bring greater development space to lithium-ion batteries. With energy and environmental issues have become increasingly prominent, and the rapid development of modern science and technology, people have higher requirements for performance of lithium-ion batteries. Since Goodenough reported the olivine-type LiFePO4 in 1997, LiFePO4 as a potential energy storage material has been of great concern for its high capacity, security, non-toxic and environmentally friendly features. It is considered as the most ideal candidate cathode material for a new generation of large-scale lithium-ion battery used for a hybrid tram or streetcar. However, due to restrictions of the crystal structure, its electronic conductivity and ion diffusion rate are very low. The commercialization of its application has been seriously hampered.The preparation of LiFePO4/C battery anode material in lithium ion battery is used lithium dihydrogen phosphate, ferric oxide and glucose as the main reactants, then LiFePO4/C was modified by Cu2+ doping. The preparation process of LiFePO4/C, the modification process of Cu2+ doping, the physical and electrochemical characterization of the product and so on were investigated systematically by using TG-DTA, XRD, SEM, BET tests, PSD, charge-discharge tests, CV and EIS methods.LiFePO4/C powders were prepared through high temperature mechanochemistry technology, the influence factors such as ball milling temperature, time, ball powder weight ratio and lithium ferrum molar ratio on the physical and electrochemical characterization were studied. Results showed that LiFePO4/C powders acquired at 600℃ for 5 h with ball powder weight ratio was 9:1 and lithium ferrum molar ratio was 1:0.96 exhibited high distribution with the particle size between 0.5～2 μm and the specific surface area is 33.59 m2/g, and showed better electrochemical performance with the charging and discharging platform about 3.4V. The first discharge specific capacity was 107.609 mAh/g at 0.1C.modified by Cu2+ doping was obtained base on the better condition of the preparation of LiFePO4/C. The effects of different Cu2+ doping and carbon coating amounts on the physical and electrochemical characterization were investigated. The results showed when the content of Cu2+ doping is 0.01 and the carbon coating is 5%, LiFe1-xCuxPO4/C powders exhibited high distribution with the particle size between 0.6～2μm, and the specific surface area is 35.12 m2/g, and showed better electrochemical performance with the charging and discharging platform about 3.4V, and the first discharge specific capacity was 138.087 mAh/g at 0.1C. The modified LiFe0.99Cu0.01PO4/C has smaller impedance during the reaction at the electrode and lithium ion migration and higher initial discharge capacity compared with undoped LiFePO4/C.