No-flash-point electrolytes applied to amorphous carbon/Li1+xMn2O4 cells for EV use

Use of no-flash-point electrolytes (NFEs) containing non-flammable solvent for an amorphous carbon/Li1+xMn2O4 cell has been studied. We prepared three NFEs: NFE1 was composed of 1 M (mol dm(-3)) of LiN[SO2C2F5](2) as supporting electrolyte, and 80 vol.% of methyl nonafluorobutyl ether (MFE) and 20 vol.% of ethyl methyl carbonate (EMC) as solvents; NFE2 was prepared by adding 0.5 M of EC (ethylene carbonate) to NFE1; and NFE3 was prepared by adding 0.1 M of LiPF6 to NFE2. Charge-discharge performance of Li1+xMn2O4/Li cells and amorphous carbon/Li cells with NFEs were investigated. The amorphous carbon/Li1-xMn2O4 18650 cells were fabricated and investigated in terms of rate capability and cycle life. NFE2 showed good rate performance. NFE3 showed the best cycle life among the NFE electrolyte cells, though it had only fair rate performance. Electrochemical impedance spectroscopy (EIS), attenuated total reflection infrared (ATR-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were measured to study the effect of EC and LiPF6. (C) 2003 Elsevier Science B.V. All rights reserved.