Influence of Ti^4＋ doping on electrochemical properties of LiFePO4/C cathode material for lithium-ion batteries

To improve the performance of LiFePO4, single phase Li（1-4x）TixFePO4/C （x=0, 0.005, 0.010, 0.015） cathodes were synthesized by solid-state method. A certain content of glucose was used as carbon precursor and content of carbon in every final product was about 3.5%. The samples were characterized by X-ray diffraction（XRD）, scanning electron microscopy observations（SEM）, charge/discharge test, carbon analysis and electrochemical impedance spectroscopy（EIS）. The results indicate that the prepared samples have ordered olivine structure and doping of the low concentration Ti^4＋ does not affect the structure of the samples. The electrochemical capabilities evaluated by charge-discharge test show that the sample with 1% Ti^4＋ （molar fraction） has good electrochemical performance delivering about an initial specific capacity of 146.7 mA·h/g at 0.3C rate. Electrochemical impedance spectroscopy measurement results show that the charge transfer resistance of the sample could be decreased greatly by doping an appropriate amount Ti^4＋.