Interesting Influence of Different Inorganic Particles on the Energy Storage Performance of a Polyethersulfone-Based Dielectric Composite

At present, dielectric capacitors have revealed large potential in the field of dielectric energy storage thanks to their advantages such as easy processing, flexibility, and long service life. Currently, a variety of methods have been proposed to prepare composite dielectrics with excellent comprehensive performance, which have the characteristics of great insulation strength, good flexibility, excellent efficiency, and large energy storage density. In this research, three composite dielectrics such as BT/PESU, BN/PESU, and TiO2/PESU are prepared by the solution casting method. Herein, we report that the incorporation of low contents of inorganic fillers into a linear polymer leads to concurrent enhancements in both permittivity and breakdown strength. The composite material is conducive to the lightweight nature and miniaturization of dielectric capacitors and at the same time promotes the development of electrical energy storage and conversion devices. The linear dielectric material polyethersulfone (PESU) is selected as the matrix, and it is planned to retain the characteristics of excellent insulation strength and small tanδ of PESU. In addition, by introducing inorganic filler phases with different particle sizes and dielectric constants, the microstructure of the composite material can be adjusted and the macroscopic properties of the composite material can be improved. At last, through comparison, a polymer-based dielectric composite with excellent breakdown strength and energy storage performance was successfully achieved. Fortunately, the discharge energy density of the 1 wt % TiO2/PESU dielectric composite reaches 7 J/cm3 at 570 kV/mm, and its charge–discharge efficiency reaches 87%. This work paves a broad road for the research and development of energy storage materials in the field of dielectric capacitors with high energy storage density, high efficiency, and excellent breakdown strength.