Structural, magnetic and electrochemical properties of lithium iron orthosilicate

摘要

We report the structural and electronic characterization of Li_2FeSiO_4 synthesized by solid-state reaction. X-ray diffraction, Raman scattering, Fourier transform infrared (FTIR) spectroscopy, electron paramagnetic resonance (EPR) spectroscopy and magnetization measurements are analyzed. Magnetic susceptibility experiments give evidence that Li_2FeSiO_4 powders possess an antiferromagnetic ordering below T_N = 25 K due to long range Fe-O-Li-O-Fe interactions. Analysis of the paramagnetic region giving the Curie-Weiss parameters theta_p = -93.5 K and C_p = 4.13 emu K mol~(-1) shows the divalent state of Fe cations. Electron paramagnetic resonance experiments confirm this electronic configuration. Electrochemical measurements were carried out in lithium cells with LiTFSI in a poly(ethylene oxide) (PEO) polymer electrolyte at 80 deg C. The resulting cyclic voltammogram indicates a stable structure for the first cycle with redox peaks at 2.80 and 2.74 V versus Li~0/Li~+.