Passivating Lithiated Graphite via Targeted Repair of SEI to Inhibit Exothermic Reactions in Early‐Stage of Thermal Runaway for Safer Lithium‐Ion Batteries

Abstract The self‐exothermic in early stage of thermal runaway (TR) is blasting‐fuse for Li‐ion battery safety issues. The exothermic reaction between lithiated graphite (LiCx) and electrolyte accounts for onset of this behavior. However, preventing the deleterious reaction still encounters hurdles. Here, we manage to inhibit this reaction by passivating LiCxin real time via targeted repair of SEI. It is shown that 1,3,5‐trimethyl‐1,3,5‐tris(3,3,3‐trifluoropropyl)cyclotrisiloxane (D3F) can be triggered by LiCxto undergo ring‐opening polymerization at elevated temperature, so as to targeted repair of fractured SEI. Due to the high thermal stability of polymerized D3F, exothermic reaction between LiCxand electrolyte is inhibited. As a result, the self‐exothermic and TR trigger temperatures of pouch cell are increased from 159.6 and 194.2 °C to 300.5 and 329.7 °C. This work opens up a new avenue for designing functional additives to block initial exothermal reaction and inhibit TR in early stage.