Additive‐Mediated Quenching of Reactive Oxygen to Mitigate Thermochemical Crosstalk in Thermal Runaway for Ni‐Rich Lithium‐Ion Batteries

Ni‐rich cathodes are regarded as promising candidates for high‐energy lithium‐ion batteries. Nonetheless, under highly delithiated and overheating conditions, cathodes can release reactive oxygen (O*), triggering internal thermochemical crosstalk reactions. Here, inspired by the β‐carotene (β‐Car) scavenging O* in nature, we propose a thermal response functional separator based on PCM‐β‐Car@SiO 2 . Using multiscale mass spectrometric and calorimetric analyses, we demonstrate that β‐Car can physically quench O* using energy transfer and terminate chain reactions by scavenging oxygen‐centered radicals. Specifically, the critical thermochemical crosstalk reactions between oxygen and the electrolyte/lithiated anode are mitigated. At the cell level, the separator is demonstrated to mitigate hazards pronouncedly under overcharge and thermal abuse conditions. The peak average temperatures during thermal runaway (TR) are reduced by 44.91% and 43.37%, respectively. Meanwhile, toxic gas emissions are reduced by 24.22% and 36.12%, respectively. Additionally, the cathode bulk exhibits the coexistence of layered and rock salt phases. The anode surface remains smooth with minor amounts of Li 2 CO 3 and Li 2 O. This work provides new insights into thermal safety separators for next‐generation high‐energy‐density lithium‐ion batteries.