Deciphering a New Electrolyte Formulation for Intelligent Modulation of Thermal Runaway to Improve the Safety of Lithium-Ion Batteries

Thermal runaway remains a persisting challenge that poses a significant risk to lithium-ion battery (LIB) users. In commercial LIBs, thermal runaway is typically controlled using temperature-responsive trilayer polypropylene/polyethylene/polypropylene (PP/PE/PP) separators. However, because of thermal shrinkage at ≈160 °C, these separators often fail to prevent thermal runaway in practical LIBs. Electrolyte engineering is, therefore, crucial to mitigate the risk of thermal runaway in LIBs. In this context, the Diels-Alder click chemistry is being introduced to tackle the thermal runaway issues in LIBs. A thermoresponsive electrolyte is proposed composed of a lithium salt dissolved in vinylene carbonate (VC) and 2,5-dimethylfuran (DMFu) that functions effectively in batteries at room temperature. At high temperatures, VC and DMFu participate in Diels-Alder reactions, forming oligomers that significantly decrease the ionic conductivity of the electrolyte and concurrently occlude the micropores of PP/PE/PP separators. These dual effects enable a two-step intelligent modulation of thermal runaway, with a warning phase activated above 80 °C and a complete thermal shutdown at 120 °C. The thermoresponsive electrolyte formulation deciphered in this study holds great potential for advancing the safety of LIBs through electrolyte engineering.