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

• Bicontinuous BST nf and BNNS arrays in anisotropic nanocomposites. • Experiments/simulations reveal bicontinuous structures enhance ɛ r and E b . • Optimized PMB-i composite achieves U e ∼18.2 J/cm³, ɛ r ∼33.6, and E b ∼550 MV/m. • Novel space structure design applicable to high-temperature energy storage. 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 0.6 S r0.4 TiO 3 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/cm 3 , 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.