Covalently Interconnected BN/CNTs Hybrid Networks Enhance the Thermal Conductivity and Electrical Insulation of Phase Change Composites for Advanced Thermal Management

ABSTRACT Achieving efficient thermal management in high‐power and flexible electronic devices remains a major challenge, particularly in the development of polymer‐based phase change materials (PPCMs). Here, we report a PPCMs constructed by embedding covalently bonded boron nitride/carbon nanotubes (BN/CNTs) hybrids into a paraffin wax/ polydimethylsiloxane (PW/PDMS) matrix, which is called PW/PDMS@BN/CNTs (PPBC). The hybrids were synthesized through dopamine‐assisted polymerization and amidation between amino‐functionalized BN and carboxylated CNTs, forming continuous, chemically connected heat transfer networks. Structural analyses confirm stable amide linkages and homogeneous dispersion of fillers. The optimized PPBC exhibits a maximum thermal conductivity of 5.92 W·m −1 ·K −1 and a maximum latent heat of 92.5 J·g −1 . It also shows excellent cycling stability and leakage resistance with < 2% mass loss after 100 cycles. Thermal management tests reveal that PPBC coatings reduce operating temperatures of lithium‐ion batteries and light‐emitting diode (LED) chips by 10°C–30°C, achieving uniform heat dissipation and long‐term reliability. In active modes, PPBC films deliver solar‐thermal and electro‐thermal conversion efficiencies exceeding 80%, remaining stable over 50 cycles. This work offers a generalizable strategy for designing flexible, high‐performance, and electrically insulating PPCMs for advanced thermal management applications.