Improved Thermal Safety of Nickel‐Rich Lithium‐Ion Batteries Enabled by MOF Modified Separator

ABSTRACT For high‐specific‐energy lithium‐ion batteries, conventional separators relying solely on thermal stability are insufficient for ensuring safety. Chemical crosstalk often occurs after thermal failure, leads to continuous self‐heating that ultimately triggers thermal runaway. Here, we design a ZIF‐67‐based functional separator that acts as a two‐way chemical interceptor, efficiently capturing both reductive gases from the anode and oxidative species from the cathode, thereby severing the self‐heating chain at its origin. Tests on 2.0 Ah NMC811||Gr pouch cells show the PI@ZIF‐67@Al 2 O 3 separator elevates the onset temperature of accelerated self‐heating from 62.8°C to 160.5°C. Remarkably, in extreme hot box test up to 300°C, pouch cells with a pure ZIF‐67 coated separator did not undergo thermal runaway, catch fire, or explode. Density functional theory calculations, gas analysis, and in situ characterization collectively confirm ZIF‐67's efficient capture of harmful species and its suppression of crosstalk‐induced reactions at the cathode. This work provides a new separator design strategy for developing high‐safety lithium‐ion batteries.