Thermally Stable Electrolyte for Lithium-Ion Batteries

The weight of gas formed by Li-ion cell components heated to 400°C was studied by DSC. Electrolyte released the most gas – over 70% of its original weight during the heat treatment, while fully charged cathode and anode released gas at 4.6% and 3.9% of their original weight, respectively. Thus, the weight of gas formed during heat treatment by various solvents, LiPF 6 , and electrolytes containing various solvents or lithium salts was studied. Solvent thermal stability was the key to reducing the gas formation of electrolyte at elevated temperature. Electrolyte containing g-butyrolactone (GBL) solvent delayed the venting of Li-ion cells by approximately 50 °C compared with conventional electrolyte containing carbonate solvents during a hot box test. Cell venting was observed to be due to gas pressure from electrolyte decomposition in the cell.