Study on the preparation and energy storage performance of GQDs/BTO/PVDF flexible composite dielectrics
Based on percolation threshold theory,the effects of barium titanate(BTO)content and quantum dot types on the dielectric properties of graphene quantum dots GQDs/BTO/polyvinylidene fluoride(PVDF)composites were investigated.The dielectric constant and loss were characterized by Fourier transform infrared spectroscopy(FTIR),transmission electron microscopy(TEM),scanning electron microscopy(SEM)and LCR measurements.Ferroelectric-piezoelectric testing was also performed to evaluate the energy storage density and efficiency.Finite element analysis was used to discuss and verify the mechanism of dielectric property improvement.The results indicate that when the BTO content increases,the relative dielectric constant of the system first increases and then decreases,reaching a maximum value of 290(5 kHz)at 10％BTO content.In contrast,the dielectric loss follows as reducing first and then increasing.The introduction of—NH2 functional groups alters the electronic structure of GQDs,thereby improves charge transfer efficiency.Moreover,the addition of quantum dot materials improves the dispersion of BTO in the matrix and enhances the relative dielectric constant of the composite system while maintaining a high breakdown field strength.This effect is most pronounced in the GQDs-NH2/BTO/PVDF system,where the dielectric constant reaches 4 713 at 5 kHz.For GQDs-NH2/BTO/PVDF composites,an energy storage density of 2.57 J/cm3 with an energy efficiency of 78.8％is achieved in an applied electric field of 210 kV/mm.This study demonstrates the effectiveness of GQDs in enhancing the dielectric performance of composite dielectrics and provides a novel research direction for improving the energy storage performance in flexible composite dielectrics.
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