Early intervention of thermal runaway by phloroglucinol-releasing microcapsules enables safe high-energy-density lithium-ion batteries

Abstract

The catastrophic thermal runaway (TR) of high-energy-density lithium-ion batteries remains a critical safety challenge, as conventional flame-retardant strategies are largely ineffective in suppressing self-accelerating reactions once initiated. Herein, we introduce an early-intervention strategy enabled by intelligent thermoresponsive microcapsules (MPs) that rupture at the incipient stage of TR (∼120 °C), releasing a phloroglucinol core. The liberated phloroglucinol reacts selectively with a lithiated graphite anode through displacement reactions, thereby reconfiguring the intrinsic TR reaction pathways. This targeted intervention suppresses the generation of reductive gases that accelerate cathode decomposition and drive the exothermic cascade. When incorporated into 1 Ah NCM811‖Gr pouch cells, the MPs exhibit excellent electrochemical compatibility, retaining 96.62% of capacity after 200 cycles. More importantly, under adiabatic and thermal abuse conditions, the TR onset temperature is delayed by 11.3 °C, and the peak temperature is drastically reduced by 202.7 °C. These results demonstrate a reaction-sequence-modulation strategy that fundamentally redefines the relationship between safety and performance, opening a pathway to next-generation high-energy-density batteries that combine intrinsic safety with long cycle life.