Flame-retardant, low-supercooling PCMs for thermal management

Phase-change materials (PCMs) offer a promising approach for passive thermal regulation in lithium-ion batteries, but their practical application is frequently limited by severe supercooling, melt leakage, and inadequate fire safety. In this study, we report a C18-alkyl-modified benzoxazine molecular PCM (BZ-PCM) that integrates crystallization regulation with intrinsic flame retardancy. Temperature-dependent FT-IR and crystallization-kinetics analyses indicate that amide-mediated hydrogen bonding plays a primary role in suppressing supercooling, while aromatic interactions may additionally assist ordered packing, thereby placing the phase-transition window at 45–55 °C. Encapsulation of BZ-PCMs within an ultralight silicon-crosslinked melamine/isonicotinic acid (Si-MA/IA) aerogel yields a shape-stabilized composite PCM (CPCM) with over 95% PCM loading, excellent leakage resistance, and a high reversible latent heat of 135.6 J/g at 53.95 °C. Upon heating, benzoxazine ring-opening polymerization triggers in situ crosslinking to form a polybenzoxazine/char barrier, providing rapid self-extinguishing behavior and significantly reduced heat release (pHRR = 319.5 W/g; THR = 40.1 KJ/g). Thermal simulations demonstrate that CPCM can attenuate temperature excursions by 19.3 °C in a model battery module. This work establishes a multifunctional materials platform that combines low supercooling, efficient reversible heat storage, and robust flame retardancy for advanced battery thermal management.