Large-scale fabrication of quasi-isotropic insulating boron nitride films with through-plane thermal conductivity exceeding 10 W m−1 K−1

Thermal management has become a critical challenge with the continuous development of high-performance electronic devices. However, achieving high through-plane and in-plane thermal conductivity within the same composite film remains a significant challenge in the design of thermal management materials. Here, a large-scale preparation of thermal management materials with isotropic high thermal conductivity and insulation properties were constructed by introduced two types of boron nitride spheres (BNs) of different diameters and boron nitride nanosheets (BNNS) as through nano-polymer engineering technology. Based on the close packing and synergistic effect of fillers, a compact three-dimensional thermal conductive network was constructed, which can significantly enhance both the thermal conductivity and insulation properties of the composite films. The fabricated composite film exhibits a dense three-dimensional hybrid network structure, resulting in a through-plane thermal conductivity of up to 11.34 W m⁻¹ K⁻¹ and an in-plane thermal conductivity of up to 9.56 W m⁻¹ K⁻¹, demonstrating excellent isotropic thermal conductivity performance. Furthermore, the composite films have significant temperature drop performance in electric device. The strategy we proposed enables the effective fabrication of three-dimensional network structures with superior quasi-isotropic heat dissipation performance for high-temperature thermal management in practical applications.