Structure–dielectric property correlation in flexible PVA/ZrO₂/g-C₃N₄/CNT nanocomposite films for advanced energy storage applications

Polymer-based nanocomposites have attracted significant attention for advanced dielectric and energy storage applications due to their tunable electrical properties and structural compliance. In this work, flexible PVA/ZrO₂/g-C₃N₄/CNT (PVA-ZGC) nanocomposite films were successfully synthesized via solution casting to investigate their structural, dielectric, and energy storage properties. Structural characterization confirmed the effective integration and homogeneous dispersion of ZrO₂, g-C₃N₄, and CNTs within the PVA framework. Elemental analysis verified the presence of C, O, Zr, and N, with no detectable impurities. The dielectric properties were evaluated over a frequency range of 0.1 Hz to 7 MHz. A substantial enhancement in functional properties was achieved by adding hybrid nanofillers. The dielectric permittivity increased by approximately 45%, accompanied by a rise in AC conductivity from 2.65 × 10⁻⁹ to 4.33 × 10⁻⁹ S cm⁻¹ at 100 Hz. Moreover, the energy density reached 2.51 × 10⁻⁶ J m⁻³ compared with 1.73 × 10⁻⁶ J m⁻³ for pristine PVA. The observed reduction in relaxation time from 5.11 × 10⁻⁵ to 2.52 × 10⁻⁵ s reflects improved polarization kinetics and more efficient charge-carrier dynamics. These enhancements are attributed to synergistic effects of high-permittivity ZrO₂, semiconducting g-C₃N₄, and conductive CNT networks, which enhance interfacial polarization and charge transport. The results showed that the fabricated nanocomposites can be used as energy storage materials with high efficiency and flexibility.