Synthesis and electrochemical properties of multi-doped LiFePO4/C prepared from the steel slag

The paper presents and discusses a novel route to synthesize a multi-doped LiFePO4/C composite by using steel slag as a raw material. A ferroalloy with suitable molar ratio of Fe, Mn, V, and Cr is recovered from the slag by a selective carbothermic method, and successfully used as source materials of Fe and multiple dopants for preparing the multi-doped LiFePO4/C. XRD and Rietveld-refined results show that the multi-doped LiFePO4/C is single olivine-type phase and well crystallized, Mn, V, and Cr atoms occupy Fe site. Elemental mapping image confirms that the elements (Fe, P, Mn, V, and Cr) distribute homogeneously in particles of the multi-doped LiFePO4/C. The electrochemical performance of prepared cathode was evaluated by galvanostatic charge/discharge and cyclic voltammogram tests. Compared to the undoped LiFePO4/C prepared only by chemical reagents, the multi-doped LiFePO4/C exhibits lesser capacity drops with increasing of charge/discharge current density due to the improvement of the electrode reactivity by multi-doping. The results suggest that steel slag is an abundant and inexpensive source materials of iron and dopants for preparing multi-doped LiFePO4/C.