Enhanced Energy Storage in AgNbO3@KH550/PVDF/PMMA Composites: Hysteresis Loop Analysis

The hysteresis loop of AgNbO3@KH550/PVDF/PMMA composites is illustrated in Figure 6b. It is evident that the ferroelectric polymer PVDF exhibits a higher Pmax value, but also a larger Pr value. On the other hand, as a linear polymer, PMMA displays a smaller Pmax and an extremely low Pr value. In the AgNbO3@KH550/PVDF/PMMA composites, as the mass fraction of PVDF increases, the hysteresis loop gradually broadens from slender to wider, and the Pr value gradually rises. However, the inclusion of a small amount of PVDF in the composites does not lead to an increase in the Pr value, indicating that PMMA has an inhibitory effect on the Pr value of PVDF in small quantities. Simultaneously, with the increase in PVDF mass fraction, the breakdown strength and Pmax value of the composites exhibit the same changing trend. Since PVDF possesses a higher polarization strength and the antiferroelectric filler AgNbO3@KH550 can induce a higher Pmax value under a high electric field, the polarization strength of the composites can be enhanced. Notably, AgNbO3@KH550, as a filler, showcases a significant saturation polarization and a minimal remanent polarization, demonstrating a double hysteresis loop, which is a characteristic feature of antiferroelectric ceramics. The substantial saturation polarization of AgNbO3@KH550 particles under a high electric field can prompt the composite material to exhibit a high Pmax value, ultimately enhancing the energy storage density of the nanocomposite. Specifically, when the mass fraction of PVDF is 30 wt%, the composite attains a Pmax value of 7.06 μC cm-2 at a breakdown strength of 430 kV mm-1, with a corresponding Pr value of 0.2 μC cm-2.