Preparation, Thermal Stability and Electrochemical Properties of LiODFB

Lithium oxalyldifluoroborate (LiODFB) was synthesized in dimethyl carbonate solvent and purified by the method of solvent-out crystallization. The structure characterization and thermal stability of LiODFB were performed by Fourier transform infrared (FTIR) spectrometry, nuclear magnetic resonance (NMR) spectrometry and thermogravimetric analyzer (TGA). LiODFB was exposed to 50% humid air at 25 °C for different time, then dried at 80 °C for 12 h, and the electrochemical properties of the cells using 1 mol/L dried LiODFB in ethylene carbonate + dimethyl carbonate + ethyl(methyl)carbonate were investigated. The results showed that, pure crystallization LiODFB was obtained; it had good thermal stability with a thermal decomposition temperature of 248 °C; when it was exposed to humid air, it was firstly converted into LiODFB·4H2O; with increasing exposure time, more and stronger impurity peaks in the X-ray diffraction (XRD) patterns of LiODFB were observed, and both the discharge specific capacity and the capacity retention decreased gradually.