XRD simulation study of doped LiFePO4

LiFePO4 has become a highly promising cathode material for use in the next generation of lithium-ion batteries, in which metal-doping is typically employed to improve the electrochemical properties. However, it is always difficult to resolve the issue that how the doping element and its position cause the microstructural changes and eventually influence the material properties. In this work, the X-ray diffraction (XRD) patterns of a series of metal-doped LiFePO4 were simulated by software MS Reflex to investigate those factors since XRD is a typical technique for the study of crystal structures. The effect of simulation conditions, doping position, and types of doping elements were discussed. The results revealed that: (1) the suitable step size should be 0.02° or less, and the simulation position had little influence on the XRD pattern; (2) the peak intensity changed with doping position, and had been affected more evidently at the Li-site compare with the Fe-site; (3) there was a close relationship between the doping elements and peak intensities in XRD patterns, and the variation degree of the peak intensity increased linearly with the atomic number of doping elements.

Research highlights▶ In this paper, software MS Reflex was first employed to simulate the XRD spectra of LiFePO4 doped with various metal atoms (or ions), and focused on the study of the comparison of peak intensity or position changes when doping carried out in different sites (Li- or Fe-site). ▶ This helps get a better understanding of the effects of the variance of doping elements or positions on the electrochemical performances.