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.