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

Abstract 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.