Ultralow-Content (Bi_0.5Na_0.5) TiO₃–NaNbO₃/PVDF-HFP Nanocomposites for Ultrahigh-Energy-Density Capacitor Applications

With the rapid development of electric vehicles, power electronics, and medical devices, high-energy-density capacitors have attracted considerable research and engineering attention. In this investigation, we added surface-coated BNT-NN ((Bi0.5Na0.5)TiO3–NaNbO3) nanoparticles into the poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) matrix to fabricate BNT-NN/PVDF-HFP nanocomposites. We found that the composite with ultralow contents of BNT-NN (0.5 wt %) exhibited an ultrahigh energy density of 36.94 J cm–3 at 800 mV m–1, which is 17.5% higher than that of the pristine PVDF-HFP film. However, as the content of BNT-NN nanoparticles increased to 1%, the energy density decreased by 10.9% to 32.9 J cm–3 at 750 mV m–1. Compared with other PVDF-based nanocomposite films reported previously, this work shows a much higher energy density. This may be attributed to the largely increasing dielectric constant at the interface between the nanoparticles and their surrounding substrate, especially for the nanocomposite with a low volume content. The calculated dielectric constant from the theoretical model considering interface parameters fits well with the experimental data, indicating that the composites possess Kmax at ultralow nanoparticle contents. Therefore, the ultralow nanoparticle-added nanocomposites show great promise for ultrahigh-energy-density capacitor applications.