Improved electrochemical performances and magnetic properties of lithium iron phosphate with in situ Fe2P surface modification by the control of the reductive gas flow rate

The growth of Fe2P was successfully regulated in the inner surface of LiFePO4 by the control of the reductive gas flow rate. The as-synthesized composites were characterized by XRD, XPS, TEM, and magnetic measurements. The experimental results indicated that the Fe2P content of the samples increases with the increasing reductive gas flow rate. Moreover, due to the effective conductive path from Fe2P, it was found that the moderate modified-Fe2P LiFePO4 sample had an excellent rate performance and cyclic stability under a high current density. It was also confirmed that LiFePO4 decorated with a moderate amount of Fe2P shows a lower charge transfer resistance and higher Li+ diffusion coefficient than that of the other samples examined in our investigation. However, excessive Fe2P modification had a negative effect on the enhancement of the electrochemical performance, which was mainly attributed to the large amount of available Fe2P; its non-electrochemical activity sacrifices the specific capacity of the LiFePO4 material. This work provides a novel method to obtain high performance by controlling the gas flow rate to optimize the amount of conducting Fe2P. Furthermore, the potential relationship between the LiFePO4 material's electrochemical and magnetic properties was investigated. It was believed that the magnetic moment is a simple and sensitive method for detecting the electrochemical performances of LiFePO4 electrode materials.