Synthesis and electrochemical properties of metals-doped LiFePO_4 prepared from the FeSO_4·7H_2O waste slag

摘要

FeSO_4·7H_2O precursor was synthesized by using raw materials, FeSO_4·7H_2O waste slag and H_3PO_4, without any purifying process. Crystalline metals-doped LiFePO_4 was prepared by heating an amorphous LiFePO_4. The amorphous LiFePO_4 was obtained via a novel ambient temperature reduction method, using the as-prepared FeSO_4·7H_2O, oxalic acid and Li_2CO_3 as raw materials. ICP analysis confirms that a small amount of Ti, Al and Ca deposited in precursor. XRD and Rietveld-refined results show that the metals-doped LiFePO_4 is single olivine-type phase and well crystallized, Ti atoms occupy Li (M1) site, resulting in the formation of cation-deficient solid solution. From SEM and corresponding elemental mapping images, it could be found that the particle size of LiFePO_4 is about 200-500 nm, and the distribution of elements (Fe, P and Ti) is homogeneous. The electrochemical performance of LiFePO_4 cathode was evaluated by galvanostatic charge/discharge test. The results indicate that the metals-doped LiFeP04, prepared from the FeSO_4·7H_2O waste slag, delivers a capacity of 161,153,145,134 and 112mAhg~(-1) at 0.1C, 0.5C, 1C, 2C and 5C rate, respectively, and shows an excellent cycling performance at moderate current rates (up to 2C).