In Situ Generation of Gel Foam via Heat-Accelerated Calcium Ion Release From Nano-CaCO3 for Lithium-Ion Battery Fire Suppression and Prevention.

Thermal runaway and its propagation in lithium-ion battery packs pose significant safety risks to energy storage systems. While complete immersion in water-based agents is an effective suppression strategy, conventional agents often fail to achieve sustained battery encapsulation because of low viscosity and rapid runoff. In this study, we report a thermally accelerated in situ crosslinking strategy to create an alginate gel foam for excellent battery fire suppression and propagation prevention. Our approach utilizes nano-CaCO3 as a dormant calcium ion source and δ-gluconolactone (GDL) as a slow acidifier. At ambient temperature, the extremely low solubility of nano-CaCO3 results in slow Ca2+ release in aqueous solution, with the mixture maintaining low viscosity and excellent foamability. After exposure to battery fire, GDL hydrolysis is accelerated, causing rapid nano-CaCO3 dissociation, Ca2+ release, and, subsequently, rapid ionic crosslinking of the alginate, which transforms the aqueous foam into a stable, adhesive gel foam. In full-scale tests, we determined that this gel foam extinguishes single-cell fires rapidly and significantly inhibits thermal runaway propagation (TRP) in multi-cell modules, outperforming water mist, water spray, and commercial aqueous film-forming foam (AFFF). This stimulus-responsive alginate gel foam offers a promising strategy for increasing the safety of lithium-ion batteries.