Dielectric and energy storage properties of the g-C₃N₄/PVDF nanocomposite thick film

The minimal difference between the dielectric constant of graphite-phase g-C₃N₄ and that of PVDF significantly reduces the local electric field distortion, thus improving the breakdown strength and energy storage density of the composites. In addition, the low conductivity (10^–12~−13 S/m) and wide band gap (2.7 eV) of g-C₃N₄ nanosheets are favorable for improving the breakdown strength of PVDF composites. In this study, g-C₃N₄/PVDF dielectric films were prepared by solution casting method using g-C₃N₄ as inorganic filler; the effects of g-C₃N₄ concentration on dielectric and energy storage properties of the composite films were discussed. The results show that the 3wt% g-C₃N₄ /PVDF composite film has the highest dielectric constant of 13 at room temperature because of its good dispersion and strong interfacial polarization. Additionally, the maximum discharge energy density is 6.85 J/cm³, which is twice that of PVDF (3.51 J/cm³) due to the formation of charge traps and enhanced mechanical properties. In this paper, a simple, low-cost and environmentally friendly method is proposed to prepare flexible composite dielectric films with high energy storage density using 2D filler g-C₃N₄.