Electrochemical performances of Co-doped LiFePO4/C obtained by hydrothermal method

LiFePO4, C-coated LiFePO4 (LiFePO4/C), and Co-doped LiFePO4/C as cathode materials for lithium ion batteries are synthesized by a hydrothermal method. The electrochemical properties of the three samples are investigated and compared by galvanostatic cycling, rate capability and cyclic voltammetry (CV) measurements. LiFePO4, LiFePO4/C, and Co-doped LiFePO4/C exhibit initial discharge capacities of 88, 90 and 116 mAh g−1 at 0.1 C, respectively. After annealing at 400 °C, the initial discharge capacities of the three corresponding samples increase to 115, 125 and 132 mAh g−1 at 0.1 C. In both cases, Co-doped LiFePO4/C shows the best rate performance among the three samples. CV measurements indicate that the improvement of dynamic behavior could be attributed to Co doping. All experimental observations indicate that the preparation of Co-doped LiFePO4/C offers a way to combine the common methods to improve the performance of LiFePO4: particle size reduction, intimate conducting phase coating and metal supervalent doping, which explain the enhanced electrochemical properties.

► This work offers combined methods to improve the performances of LiFePO4.
► Hydrothermal method has been firstly utilized to prepare Co-doped LiFePO4/C.
► Cation order, particle size and electronic contact are three decisive factors.