Reinforced energy storage performance of poly(vinylidene fluoride) composite films by filling with surface fluorinated one-dimensional barium titanate nanofibers

One-dimensional barium titanate nanofibers/poly(vinylidene fluoride) (PVDF) composite films were prepared by casting technology. To improve the dispersion of nanofibers in the PVDF matrix and enhance the interface bonding between nanofibers and the PVDF matrix, surface modification of nanofibers was obtained by fluorination treatment. Experimental and theoretical simulation studies were conducted to investigate the effects of surface fluorination-modified one-dimensional barium titanate nanofibers on the micro morphology, structure, dielectric constant, and energy storage density of PVDF composite films. The results showed that the barium titanate powder synthesized by electrospinning had a good one-dimensional fiber morphology, with a diameter of 70–130 nm and a length of 4–15 µm. The surface fluorination treatment was able to significantly improve the dispersion and bonding of the one-dimensional barium titanate nanofiber in the PVDF matrix. As the filling volume of the one-dimensional nanofibers increased, the dielectric constant of the PVDF composite film significantly increased. When the filling volume of the surface fluorinated one-dimensional barium titanate nanofiber was 7.5 vol%, the room temperature dielectric constant of the PVDF composite film reached 21.8, and the surface fluorinated one-dimensional barium titanate nanofiber/PVDF composite film exhibited lower dielectric loss and high breakdown strength. When the filling volume of the surface fluorinated one-dimensional barium titanate nanofiber was 2.5 vol%, the energy storage density of the PVDF composite film was 7.9 J/cm3, which was 2.82 times that of pure PVDF. The improvement of energy storage performance can be attributed to the good dispersion of the surface fluorinated barium titanate nanofibers in the PVDF matrix and the good interface situation. Finite element simulation further revealed that the surface fluorinated one-dimensional nanofibers could effectively improve the breakdown strength of the composites. That provides a promising way to enhance the dispersion and interface bonding of filler in polymer matrices, thereby achieving high-performance composites with high dielectric constant, high breakdown strength, and excellent energy storage density.