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 poses a significant safety challenge, as existing flame-retardant strategies often fail to halt its self-accelerating nature during late stages. Herein, we propose an early-intervention strategy by designing intelligent thermoresponsive microcapsules (MPs) that release phloroglucinol core at the incipient stage of TR (~120 °C). The released phloroglucinol preemptively consumes the lithiated graphite anode through displacement reactions, thereby altering the intrinsic TR reaction pathways. This intervention effectively suppresses the generation of reductive gases that trigger cathode decomposition, leading to a markedly mitigated heat release cascade. When incorporated into 1 Ah NCM811||Gr pouch cells, the MPs exhibit excellent electrochemical compatibility, demonstrating a high capacity retention of 96.62% after 200 cycles. More importantly, under adiabatic and thermal abuse conditions, the TR trigger temperature is delayed by 11.3 °C, and the peak temperature is drastically reduced by 202.7 °C. This work provides a groundbreaking reaction-sequence-modulation strategy, paving the way for developing high-energy-density batteries without compromising safety or cycle life.