Influence of iron phosphate on the performance of lithium iron phosphate as cathodic materials in rechargeable lithium batteries

Iron phosphate (FePO 4 ·2H 2 O) has emerged as the mainstream process for the synthesis of lithium iron phosphate (LiFePO 4 ), whereas FePO 4 ·2H 2 O produced by different processes also has a great influence on the performance of LiFePO 4 . In this paper, FePO 4 ·2H 2 O was produced by two different processes, in which FeSO 4 ferrous and Fe(NO 3 ) 3 ·9H 2 O ferric were used, respectively. After dehydration under the same conditions, a carbon-coated lithium iron phosphate (LiFePO 4 /C) cathode material was synthesized by a high-temperature solid phase method. The results demonstrated that FePO 4 ·2H 2 O contained different impurities due to different raw materials, which led to different particle sizes, specific surface areas, microscopic morphology, and crystal structures. The difference of FePO 4 ·2H 2 O eventually resulted in the difference of LiFePO 4 /C cathode materials in micro-morphology and crystal structure, which affected the electrochemical performance. Under the premise of comprehensively considering the cost and quality of FePO 4 ·2H 2 O, improving the purity of FePO 4 ·2H 2 O is an important method to improve the electrochemical performance of LiFePO 4 /C cathode materials. Simultaneously, it is also expected to provide theoretical guidance for the preparation of lower-cost and better-quality LiFePO 4 /C cathode materials.