Synthesis and electrochemical characterization of F- and Cl-doped Li2FeSiO4 cathode material for lithium-ion battery

Abstract

As a high-capacity cathode material with a considerable cycle life, lithium metal orthosilicates have attracted much attention. In this paper, Li 2 FeSiO 4 , Li 2-FeSiO 4-x Cl x and Li 2 FeSiO 4-x F x are successfully synthesized via solid-state method. Li 2 FeSiO 4-x F x is also composited with reduced graphene oxide (rGO). The X-ray diffraction patterns show 0.2% expansion in the lattice volume of Li 2 FeSiO 4-x F x and 0.7% shrinkage for Li 2 FeSiO 4-x Cl x due to the doping effect. Fourier-transform infrared spectroscopy also indicates a frequency shift for [SiO 4 ] 4and [LiO 4 ] functional groups due to ion doping. The SEM images confirm that rGO surrounded Li 2 FeSiO 4-x F x microparticles. The electrochemical performance illustrates a reversible ox/red reaction of Fe 2? /Fe 3? couple at the potential of 3/2.6 V for Li 2 FeSiO 4 , 3.5/2.9 V for Li 2 FeSiO 4-x F x , and 3.3/2.3 V for Li 2 FeSiO 4-x Cl x . Lithiation curves at 0.05C rate show the first specific capacity of 168 mAh g -1 for Li 2 FeSiO 4 with 84% retention after 25th cycles, 190 mAh g -1 for Li 2 FeSiO 4-x F x with 100% retention, and 120 mAh g -1 for Li 2 FeSiO 4-x Cl x with 73% retention. Li 2 FeSiO 4-x F x /rGO cathode delivers 265 mAh g -1 with 88% retention after 25th cycles.

A critical review on orthosilicate Li2MSiO4 (M = Fe, Mn) electrode materials for Li ion batteries

“…Tahertalari et al [209] studied effect of F and Cl doping at O site in LFS. LFS, Li 2 FeSiO 4−x Cl x and Li 2 FeSiO 4−x F x /rGO.…”