A Detailed Investigation of the Thermal Reactions of LiPF[sub 6] Solution in Organic Carbonates Using ARC and DSC

Abstract

The thermal stability of 1 M solutions in mixtures of ethylene carbonate, diethyl carbonate, and dimethyl carbonate in the temperature range of 40 to 350°C was studied by accelerating rate calorimeters (ARC) and differential scanning calorimeters (DSC). Nuclear magnetic resonance (NMR) was used to analyze the condensed reaction products at different reaction stages. Studies by DSC and pressure measurements during ARC experiments with solutions detected a gas-releasing endothermic reaction starting at ∼170°C, involving diethyl carbonate which occurs before a number of exothermic reactions, which follow as the temperature increases. Fluoride ions are released and react with the alkyl carbonate molecules both as bases and as nucleophiles. The bulk analysis by NMR shows that and polymer are major products. Gas analysis by NMR and Fourier transform infrared spectroscopy shows and as major gaseous products of the thermal reaction of these solutions. © 2003 The Electrochemical Society. All rights reserved.