Effects of suface hydroxylated strontium titanate nanofibers on dielectric and energy storage properties of polyvinylidene fluoride composites

Abstract

With the rapid development of the electronics industry, the dielectric materials with high energy storage density, fast charge and discharge speed, easy-to-process and easy-to-mold, and stable performance are urgently needed to meet the requirements for lightweight and miniaturization of electronic component equipment. Dielectric ceramics has a high dielectric constant, but low breakdown field strength. Polyvinylidene fluoride (PVDF) has the advantages of good flexibility, high breakdown field strength, and light weight, but its dielectric constant is low. Achieving the ability to tailor the interface between dielectric ceramics filler and PVDF polymer matrix is a key issue for realizing the desirable dielectric properties and high energy density in the nanocomposites. As a result, much effort has been made to prepare the polymer composites through the surface modification of the nanoparticles with high dielectric constant fillers dispersed in a matrix, with the hope of preparing composites containing the high dielectric constant of the ceramic fillers and the high breakdown strength of polymers. In this work, in order to obtain the high dielectric-constant and high-energy-storage-density dielectric ceramics, the electrospinning method is used to prepare the SrTiO<sub>3</sub> one-dimensional nanofibers as the inorganic fillers and the casting method is adopted to prepare PVDF as the polymer matrix. To improve the interface between inorganic nanofiber fillers and PVDF matrix, the SrTiO<sub>3</sub> nanofibers are modified by surface hydroxylation. The effects of suface hydroxylated SrTiO<sub>3</sub> nanofibers on the dielectric properties and energy storage properties of PVDF composites are studied. The correlation between interface modification and energy storage performance of composites is investigated to reveal the mechanism of enhanced energy storage performance of SrTiO<sub>3</sub> nanofibers/PVDF composites. The results show that the dispersion of surface-hydroxylating SrTiO<sub>3</sub> nanofibers in PVDF polymer can be improved. The composites exhibit improved dielectric properties and enhanced breakdown strength. When the filling quantity of the surface-hydroxylating SrTiO<sub>3</sub> nanofiber fillers is 2.5 vol%, the energy storage density of the composite reaches 7.96 J/cm<sup>3</sup>. Suface-hydroxylating SrTiO<sub>3</sub> nanofibers exhibit excellent dispersion in the PVDF polymer matrix and strong interfacial adhesion with the matrix, leading the composites to possess excellent dielectric constant and energy storage performance. The surface hydroxylation of ceramic fillers can improve the energy storage performance of the composites.