Electrochemical and spectroscopic studies on carbon-coated and iodine-doped LiFeBO3 as a cathode material for lithium-ion batteries

In this study, monoclinic LiFeBO3 was carbon-coated and iodine doped via a solid-state reaction to improve the electrochemical performance of pristine LiFeBO3 as cathode material in lithium-ion batteries. In order to enhance the electrical conductivity of LiFeBO3, the highly electronegative iodide anion was doped in a limited amount (x = 0.005) at the oxygen site of the borate to produce LiFeBO3-xI2x. A thin carbon layer was then deposited in situ on the LiFeBO2.995I0.01 particles (to produce LFBI/C ) to protect them from air and moisture. Field-emission scanning electron microscopy (FE-SEM) data indicated the aggregated morphology of the synthesized samples. Powder X-ray diffraction (XRD) and Li-7 magic angle spinning (MAS) nuclear magnetic resonance (NMR) measurements revealed that both the doped and undoped LiFeBO3-based samples had mainly monoclinic structures, although a small amount of a vonsenite-type phase was formed upon iodine doping. X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDX) data confirmed the successful insertion of iodine in the cathode material. The specific discharge capacity of LFBI/C at 0.05 C rate (144.68 mAh g(-1)) was higher than that of carbon-coated LiFeBO3 (122.46 mAh g(-1)). The increased capacity of LFBI/C was also evident in long charge-discharge cycles conducted at 1 C rate and in the overall rate performance. Interestingly, the iodine-doped sample exhibited significantly high specific discharge capacity even at 10 C rate.

Automated summary

In this study, carbon-coated and iodine-doped monoclinic LiFeBO3 was synthesized to enhance its electrochemical performance as a cathode material in lithium-ion batteries. The introduction of iodine as a highly electronegative dopant and the deposition of a thin carbon layer effectively improved the conductivity and stability of the material. The synthesized LFBI/C exhibited higher specific discharge capacity and superior rate performance compared to carbon-coated LiFeBO3, with significantly high capacity retention even at high charging rates.