Preparation and performance study of novel polyurethane-based composite phase change materials for battery thermal management

Solid–liquid phase change materials are promising for thermal management, but their leakage and low thermal conductivity limit practical applications. In this study, a novel PU@BNNSs/CF solid–solid composite phase change material was prepared by vacuum impregnation using polyurethane constructed with polyethylene glycol as the phase change matrix, boron nitride nanosheets as thermally conductive fillers, and copper foam as the supporting framework. The composite showed good shape stability without obvious leakage at 80 °C. It had a melting temperature of 54.13 °C and a melting enthalpy of 82.64 J/g. After 200 heating–cooling cycles, the melting enthalpy decreased by only 0.98%, indicating excellent thermal reliability. Owing to the multiscale thermal conduction network formed by BNNSs and CF, the thermal conductivity of PU@BNNSs/CF reached 2.96 W/(m·K), which was 18.5 times that of PEG. In the heating-plate test, the surface temperature was reduced from 72.1 °C to 49.2 °C after 600 s, corresponding to a temperature reduction of 22.9 °C. Battery module simulations showed that a 4 mm PU@BNNSs/CF coating effectively reduced the maximum module temperature by 24.60, 38.19, and 47.23 °C under 3C, 4C, and 5C discharge conditions, respectively. In addition, its volume resistivity reached 1.7 × 10 10 Ω·cm, meeting the electrical insulation requirement for battery thermal management. These results demonstrate that PU@BNNSs/CF is a promising electrically insulating and highly thermally conductive composite phase change material for passive thermal management of power batteries.