Bicontinuous-distributed nanofibers and nanosheets facilitate anisotropic nanocomposite dielectrics to high energy density capacitors

Polymer nanocomposite dielectrics with high insulation and high energy storage density (U _e) are pivotal for advancing lightweight and integrated power devices. However, the inherent trade-off between dielectric constant (ɛ _r) and breakdown strength (E _b) has limited the energy storage performance of such materials. Here, we present a novel design of bicontinuous structural anisotropic nanocomposites by integrating high- ɛ _r Ba_0.6S_r0.4TiO₃ nanofiber (BST nf) arrays and oriented wide-bandgap BN nanosheets (BNNS). This architecture simultaneously enhances polarization continuity and establishes a high-specific-area carrier blocking layer, enabling the synergistic improvement of ɛ _r and E _b. Our optimized PVDF/ m BST nf/BNNS nanocomposite achieves an ultrahigh E _b of 550 MV/m and an U _e as high as 18.2 J/cm³, representing enhancements of 46 % and 323 %, respectively, over pristine PVDF. Moreover, the bicontinuous structure improves energy storage performance at elevated temperatures, providing a robust framework for designing high-performance dielectrics, which provides scientific support for the application of polymer-based energy storage devices.