Oxidation Stability and Electrochemical Properties of Organo-Fluorine Compounds for Lithium Ion Batteries

Abstract

Differential scanning calorimetry (DSC) study demonstrated that mixing of fluoro-ethers and fluoro-carbonates improved the thermal stability of 0.67 mol/L LiClO4-EC (ethylene carbonate) / DEC (diethyl carbonate) / PC (propylene carbonate) (1:1:1 vol.). Oxidation currents were smaller in the fluorine compound-mixed electrolyte solutions than in 0.67 mol/L LiClO4-EC/DEC/PC, which shows also high stability of the fluorine compound-mixed electrolyte solutions against electrochemical oxidation. Electrochemical reduction of fluorine compounds took place at the higher potentials than EC, DEC and PC as suggested by HOMO and LUMO energies of fluorine compounds. However, charge/discharge experiments using natural graphite electrodes showed that the fluorine compounds increased first coulombic efficiencies due to quick formation of SEI on natural graphite in PC-containing solvents.