Thermal Decomposition of LiPF[sub 6]-Based Electrolytes for Lithium-Ion Batteries

The thermal decomposition of lithium-ion battery electrolytes in one or more carbonate solvents has been investigated. Electrolytes containing diethyl carbonate (DEC), ethylene carbonate (EC), a 1:1 mixture of EC/dimethyl carbonate (DMC), and a 1:1:1 mixture EC/DMC/DEC have been investigated by multinuclear nuclear magnetic spectroscopy, gas chromatography with mass selective detection, and size exclusion chromatography. Thermal decomposition affords products including: carbon dioxide , ethylene , dialkylethers , alkyl fluorides (RF), phosphorus oxyfluoride , fluorophosphates , fluorophosporic acids , and oligoethylene oxides. The mechanism of decomposition is similar in all /carbonate electrolytes. Trace protic impurities lead to generation of , which autocatalytically decomposes and carbonates. The presence of DEC leads to the generation of ethylene, while the presnce of EC leads to the generation of capped oligothylene oxides .