Mg/Zn-coordinated solid–solid phase change material with intrinsic flame retardancy for battery thermal management

Phase change materials (PCMs) have attracted increasing attention as passive thermal management solutions for lithium-ion batteries due to their high latent heat and temperature regulation capability. However, conventional solid–liquid PCMs suffer from intrinsic limitations, including leakage during phase transition, low thermal conductivity, and high flammability. In this work, an intrinsically flame-retardant solid–solid composite PCM (CPCM) with high thermal conductivity is designed through hydroxide complexation of polyethylene glycol phosphate. Phosphorus pentoxide is esterified with polyethylene glycol to form polyethylene glycol phosphate, which subsequently reacts with magnesium and zinc hydroxides to construct a metal–organic framework–structured polymer complex. This molecularly integrated architecture converts the phase transition from solid–liquid to solid–solid, effectively eliminating leakage while imparting intrinsic flame retardancy. The resulting CPCM exhibits excellent shape stability with no leakage at 150 °C, a high thermal conductivity of up to 2.24 W m −1 K −1 , and outstanding fire safety performance, with a peak heat release rate reduced to 310.67 kW m −2 . The CPCM effectively suppresses temperature rise and the time of thermal runaway propagation is delayed to 298 s. This study provides a viable molecular design strategy for addressing leakage, flammability, and heat-transfer limitations of PCMs.