Advancing Thermal Safety System for Battery Pack: Introducing Intrinsic Flame‐Retardant Solid–Solid Phase Change Materials with Melamine Crosslink

Abstract Composite phase‐change materials (CPCMs), with their substantial latent heat storage and release capabilities at a consistent transition temperature, are extensively employed in diverse thermal‐energy‐storage applications. However, the risk of thermal runaway remains a significant challenge owing to the flammability and potential leakage of CPCMs. Attempts to develop flame‐retardant PCMs using various fireproof polymers through physical methods exist. In this study, a novel multifunctional flame‐retardant solid–solid phase‐change material is developed through a chemical modification process, incorporating polyethylene glycol 2000, boric acid, phosphorus pentoxide (P 2 O 5 ), expanded graphite, ammonium polyphosphate (APP), and melamine (MA). This composite material exhibits superior flame retardancy and thermal stability, making it highly suitable for enhancing the safety of battery modules. Experimental results demonstrate that PCAM2, containing 20 wt% MA and 8 wt% APP, maintains 97.75% mass retention at 250 °C for 5 h and achieves the V‐0 rating (burning stops within 10 s) according to the UL‐94 standard. Moreover, a battery module incorporating PCAM2 demonstrated superior thermal‐management capabilities than three other modules. Even after ten cycles at a 2C discharge rate, it maintained a peak operating temperature below 60 °C. Notably, the flame‐retardant CPCM films exhibited significant thermal propagation time, indicating superior temperature control and the ability to inhibit thermal runway. The intrinsically flame‐retardant CPCM developed in this study holds considerable promise for use in next‐generation thermal safety systems for electric‐vehicle battery packs and energy‐storage applications.