LiFePO4/C via fluoride doping

Non-stoichiometric compound fluoride-doped LiFePO 4 /C cathode materials were synthesized via solid-state reaction using MgF 2 and AlF 3 as dopant. The fluoride-doped LiFePO 4 /C samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical testing. The results show that the materials are well crystallized and fluoride doping cannot change the space structure of LiFePO 4 . Slight amounts of Fe 2 O 3 with no fluoride impurity were detected. Charge-discharge curves show that fluoride-doped samples have higher capacity at low rates compared with undoped LiFePO 4 /C. AlF 3 -doped samples have highest capacity at high discharge current. Both doped samples have larger polarization voltage than undoped samples. All samples exhibit good cycle stability.