Achieving excellent energy storage performance and thermal stability simultaneously in PVDF-based nanocomposites by designing the bismuth layer-structured fillers

Polymer-based dielectric materials exhibit several advantages, including high power density and rapid charge/discharge rates, making them widely applicable across various fields. However, their inherently low energy density restricts their applications in energy storage. To overcome this limitation, this study introduces novel bismuth-layered Bi 2 LaTiNbO 9 (BLTN) nanosheets as inorganic fillers, applied to the design and fabrication of PVDF-based energy storage films. The moderate dielectric constant of BLTN helps mitigate the uneven electric field distribution caused by dielectric mismatch between the high-dielectric ferroelectric filler and the polymer matrix. The [Bi 2 O 2 ] 2+ layer of BLTN functions as an insulating shell, inhibiting the movement of free electrons, thus reducing leakage current and conduction losses within the polymer matrix. The [LaTiNbO 7 ] 2− polarization layer contributes to the enhancement of polarization strength. Additionally, the higher bandgap ( E g ) of BLTN nanosheets further enhances the breakdown electric field within polymer-based materials. Consequently, the 1.5 wt% BLTN-P(VDF-HFP) nanocomposite film achieves an outstanding recoverable energy density of 25.1 J/cm 3 and energy efficiency of 78.6% at 580 kV/mm, significantly surpassing that of pure P(VDF-HFP). Furthermore, the 1.5 wt% BLTN-P(VDF-HFP) composite also demonstrates excellent thermal stability within the temperature range of 25–125 °C. These results suggest that bismuth-layered BLTN nanosheets serve as highly effective fillers for PVDF-based energy storage materials, offering greater design flexibility in the development of advanced flexible nanocomposite energy storage films.