Cation-substituted LiFePO4 prepared from the FeSO4·7H2O waste slag as a potential Li battery cathode material

Abstract The purpose of this study is to utilize the huge FeSO 4 ·7H 2 O waste slag produced by the titanium dioxide industry. FeC 2 O 4 ·2H 2 O precursors are synthesized at various pH values by using the waste slag and H 2 C 2 O 4 ·2H 2 O as raw materials, and without any purifying process. ICP analysis confirms that the impurity content of FeC 2 O 4 ·2H 2 O increases with the pH value. Crystalline cation-substituted LiFePO 4 are prepared from the FeC 2 O 4 ·2H 2 O precursors. The cation dopants do not obviously change the structure of LiFePO 4 , and all the samples are single olivine-type phase and well crystallized. The lattice parameters of LiFePO 4 decrease with the increased dopants contents. The dopants limit the size of LiFePO 4 nanocrystals, LiFePO 4 particles agglomeration and, consequently, improve the electrochemical performance of LiFePO 4 . The cation-substituted LiFePO 4 prepared from the waste slag show much better electrochemical properties than the pure LiFePO 4 at high current rates. The optimal pH value for synthesizing FeC 2 O 4 ·2H 2 O from the waste slag is about 1.0, with 96.6% iron recovery. The cation-substituted LiFePO 4 prepared from this precursor exhibits the best electrochemical properties, which delivers a capacity of 152, 142 and 126 mAh g −1 at 1 C , 2 C and 5 C rate, respectively, and shows excellent cycling performance.