Safety Improvement of Lithium Ion Batteries by Fluorine Compounds

Abstract

Thermal stability，electrochemical oxidation stability and charge/discharge characteristics of natural graphite powder were investigated by mixing of five fluoro-carbonates with 1 mol/L LiCIO4-EC/DEC/PC (1:1:1 vol.). DSC study revealed that thermal stability of the electrolyte solution was improved by mixing of fluoro-carbonates by 10.0-33.3 vol.%. Electrochemical oxidation stability was also improved. Oxidation currents for Pt electrode were significantly decreased by mixing of fluoro-carbonates. In the fluoro-carbonate-mixed electrolyte solutions，e lectrochemical reduction of PC decreased with increasing concentration of fluoro-carbonate and current density. As a result，first coulombic efficiency for natural graphite electrode increased， that is，irreversible capacity decreased in the fluoro-carbonate-mixed solutions.