Effect of surface fluorination treatment of strontium titanate nanofibers on the dielectric energy storage performance of PVDF dielectric composite films

The interface is a key factor affecting the energy storage performance of dielectric composite materials. In order to prepare high-performance dielectric composite films, one-dimensional strontium titanate (SrTiO₃) nanofibers were synthesized via electrospinning in this study and subsequently subjected to surface fluorination treatment. A one-dimensional SrTiO₃ nanofiber/polyvinylidene fluoride (PVDF) composite film system was prepared using the casting process. By combining experimental research with theoretical modeling, the influence of surface-fluorinated SrTiO₃ one-dimensional nanofibers on the microstructure, dielectric behavior, and energy storage performance of the PVDF-based composite system was thoroughly examined. Experimental characterization shows that SrTiO₃ nanomaterials prepared by electrospinning exhibit typical one-dimensional fiber morphology characteristics, with fiber diameters ranging from 50-110 nm and lengths ranging from 4-10 μm, and excellent dispersion properties. Surface fluorination treatment effectively enhances the dispersion uniformity and interfacial bonding strength of nanofibers in the polymer matrix. The dielectric performance test results show that with the increase of functionalized nanofiber content, the dielectric constant of the SrTiO₃ nanofiber/ PVDF composite film shows a significant upward trend. When the volume fraction of fluorinated modified SrTiO₃ nanofibers is 7.5vol%, the dielectric constant of the SrTiO₃ nanofiber/ PVDF composite system at room temperature reaches 18.7, while exhibiting better dielectric loss control characteristics and breakdown field strength performance. Energy storage performance analysis shows that when the filling amount of SrTiO₃ nanofibers treated with surface fluorination reaches 2.5vol%, the energy storage density of the SrTiO₃ nanofiber/ PVDF composite film increases to 7.92 J/cm³, which is 172% higher than that of pure PVDF. The performance improvement mechanism mainly stems from the dual effects brought by fluorination treatment. The finite element simulation further verified that surface fluorination treatment can effectively regulate the electric field distribution and significantly improved the breakdown field strength of SrTiO₃ nanofiber/ PVDF composite films.