Thermally Stable Electrolyte for Lithium-Ion Batteries

The demand for safer, thermally stable lithium-ion batteries (LIBs) has driven the search for advanced electrolyte systems. This study introduces an electrolyte based on propylene glycol diacetate (PGDA) to improve thermal safety and stability. The optimized PGDA-based solvent mixture increases the flash point to 100 degrees C, which is approximately 63 K higher than that of the reference electrolyte LP40 (1 M LiPF6 in EC:DEC 1:1 wt). While the flash point is primarily determined by the solvent composition, the onset of exothermic reactions depends on the conducting salt. Replacing lithium hexafluorophosphate (LiPF6) with lithium bis(oxalato)borate (LiBOB) significantly improves thermal stability, cycling performance, and safety, as cells with LiBOB retain over 97% of their capacity after 100 cycles at 40 degrees C at C-rates up to 1C. Thermal abuse tests up to 300 degrees C exhibit no exothermic reactions, thereby preventing dangerous thermal runaways. These findings underscore the potential of PGDA-based electrolytes, especially when paired with LiBOB, for safer and more robust LIB applications.