Polyethylene glycol with hydroxylated ammonium polyphosphate flame-retardant phase change composites for thermal storage

Abstract

Efficient thermal management remains a key challenge in lithium-ion battery systems, as temperature fluctuations can compromise performance and safety. Composite phase change materials (CPCMs) offer high latent heat and passive temperature regulation but are often hindered by leakage and flammability. In this study, a passive battery thermal management system incorporating an intrinsically flame-retardant CPCM was developed. Hydroxylated ammonium polyphosphate (HAPP) was synthesized through a cation-exchange reaction and integrated into a hexamethylene diisocyanate (HDI)-crosslinked polyethylene glycol (PEG) network, providing structural support and flame-retardant functionality. A Polyethylene glycol (PEG)/Hexamethylene diisocyanate (HDI)/HAPP/expanded graphite (EG) composite, denoted as PHHE, was prepared through chemical crosslinking. The resulting three-dimensional HAPP-PEG-HDI network effectively restricted the macroscopic leakage of PEG. PHHE exhibits an initial latent heat of 111.35 J/g and a mass retention of 99.88% after aging at 80 °C for 5 h. During battery-module testing at a discharge rate of 2 C, the PHHE-based battery module reached a maximum temperature of 52.08 °C, indicating its passive temperature-regulation capability. These results demonstrate that PHHE integrates thermal-energy storage, shape stability, flame-retardant functionality, and battery temperature regulation, providing a potential material approach for the thermal management of battery packs and related energy-storage systems.

Keywords

Thermal management / lithium-ion battery module / composite phase change materials / intrinsic flame retardancy / chemical crosslinking strategy

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