Three-dimensional BaTiO3 (3D BT)/polyvinylidene fluoride (PVDF) composite dielectrics were fabricated by inversely introducing PVDF solution into a continuous 3D BT network, which was simply constructed via the sol-gel method using a cleanroom wiper as a template. The effect of the 3D BT microstructure and content on the dielectric and energy storage properties of the composites were explored. The results showed that 3D BT with a well-connected continuous network and moderate grain sizes could be easily obtained by calcining a barium source containing a wiper template at 1100 °C for 3 h. The as-fabricated 3D BT/PVDF composites with 21.1 wt% content of 3D BT (3DBT–2) exhibited the best comprehensive dielectric and energy storage performances. An enhanced dielectric constant of 25.3 at 100 Hz, which was 2.8 times higher than that of pure PVDF and 1.4 times superior to the conventional nano–BT/PVDF 25 wt% system, was achieved in addition with a low dielectric loss of 0.057 and a moderate dielectric breakdown strength of 73.8 kV·mm−1. In addition, the composite of 3DBT–2 exhibited the highest discharge energy density of 1.6 × 10−3 J·cm−3 under 3 kV·mm−1, which was nearly 4.5 times higher than that of neat PVDF.

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Three-dimensional (3D) ceramic network has advantages over conventional ceramic nanoparticles in achieving high-performance flexible polymer dielectrics. However, the energy storage capacity cannot be substantially improved due to the relatively large dielectric loss and low breakdown strength. In this study, hierarchical 3DBT/EP-GO (GEBT) dielectric hybrid composites with greatly improved permittivity and energy storage density were obtained by reversely introducing the mixed graphene oxide (GO)/epoxy (EP) solution into three-dimensional BaTiO3 (3DBT) network, which was facilely constructed by sol-gel method using cleanroom wiper as template. A relatively high dielectric constant (ε′ = 15.6) and breakdown strength (E0 = 239.8 kV·mm− 1) were simultaneously achieved for the GEBT-4 system with ~ 15.4 wt% of 3DBT and 0.75 wt% of GO (to the epoxy), which were much superior to the GEBT-1 with only 15 wt% 3DBT (ε′ = 9.2, E0 = 128.8 kV·mm− 1) and epoxy nanocomposite with even 25 wt% BT nanoparticles (ε′ = 6.3, E0 = 121.0 kV·mm− 1). The continuous 3DBT ceramic network provided effective polarization pathway within epoxy matrix, while GO was helpful to prevent electrical breakdown of composites, thereby resulting in the significantly enhanced energy storage performance.