Study of fluorine substitution effect at oxygen site of LiFeBO3 cathode material for lithium-ion battery

Abstract

Fluorine substituted LiFeBO3 at oxygen site, LiFeBO3-xF2x (LFeBF, x = 0, 0.05, 0.1, 0.2, 0.3, and 0.5), have been synthesized by solid-state reaction method to improve electrochemical properties as a cathode material of lithium-ion batteries. The structural studies of LFeBF depending on fluorine substitution ratio have been performed with X-ray diffraction (XRD) and 7Li magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy, which results show the structure of samples are changed from monoclinic to vonsenite. The morphology and elemental maps have been observed by scanning electron microscopy (SEM) combined energy dispersive X-ray (EDX) spectrometer. The SEM images of LFeBF showed the morphology change with increasing fluorine substitution ratio. The electrochemical study is performed by galvanostatic charge and discharge test with the potential range of 1.0 – 4.5 V. The results have shown that fluorine substitution at oxygen site of LiFeBO3 has effectively improved electrochemical performance with the highest discharge capacity of 363.98 mAh g-1 at 0.05 C rate for LFeBF (x = 0.3).