Infrared spectroscopy of instantaneous decomposition products of LiPF6-based lithium battery electrolytes

Thermal gravimetric analysis and Fourier transform infrared spectroscopy is performed on the gaseous decomposition products evolved from two LiPF6/organic liquid-based battery electrolytes. During the heating of the electrolytes all gases are continuously transferred to the spectrometer in order to record instantaneous reaction products. We clearly detect PF5 and POF3 that are signatures of the PF6− anion self-dissociation and the decomposition reaction with trace amounts of water; as well as the neat organic solvents. Literature suggests a polymerization process of the carbonate solvents under the release of CO2 as the decomposition route in degradation studies on stored electrolytes. In contrast to that, we detect no CO2 over the whole temperature range and therefore suggest the initial decomposition route to simply consist of solvent evaporation and the thermally driven anion self-dissociation.