Electrochemical Properties of Nonflammable Organo-Fluorine Compounds for Lithium Ion Batteries

Abstract

Electrochemical behavior of organo-fluorine compounds with high oxidation stability has been investigated. Oxidation currents of fluorine compound-containing EC/DEC solutions were much smaller than those of EC/DEC and EC/DEC/PC at the higher potentials than 6 V vs Li/Li+. Electrochemical reduction of fluorine compounds started at ca. 2 V vs Li/Li+ higher than those for EC, DEC and PC. However, first coulombic efficiencies for natural graphite electrodes in fluorine compound-containing EC/DEC mixtures were nearly the same as those in EC/DEC without increase in irreversible capacities. Furthermore first coulombic efficiencies in fluorine compound-containing EC/DEC/PC mixtures were much larger than those in EC/DEC/PC itself. The results show that the fluorine compounds used in the present study can be used as non-flammable solvents for lithium ion batteries.