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.

The rapid development of the clean energy industry has given great impetus to energy-efficient storage and conversion technologies. Film capacitors have attracted much attention because of their higher charge and release rates, greater energy density, and extended life cycle. But the lower recharging and discharging efficiency and insulation properties pertaining to the electricity used in capacitors limit the improvement of their energy storage performance. In this paper, the addition of the linear polymer polycarbonate (PC) to polyvinylidene fluoride (PVDF) through a blending strategy and the subsequent acquisition of the high-dielectric nanofiller titanium dioxide (TiO2) to the blended matrix is expected to achieve synergistic optimization of the insulation and polarization properties, thereby enhancing the energy storage performance of the mixed media. The findings show that great storage of energy productivity (U e ≈ 11.43 J/cm3, η ≈ 57.08%) is obtained for 40 vol % PC/PVDF-x wt %-TiO2 at an optimum field strength of 450 kV/mm when the TiO2 doping amount x is 0.9 wt %. Compared with pure PVDF, its U e is improved by 2.3 times, η by 1.2 times, and E b by 1.5 times. This research presents a viable answer for applying PVDF-based high-energy-storage film capacitors.

In modern electronics and power systems, good-performance dielectric capacitors have an essential function. Polymer-based dielectrics are widely used in the field of dielectric capacitors because of their large dielectric constant, flexibility, low density, and ease of processing. At present, ferroelectric polymers suffer from low breakdown field strength and high dielectric losses. How to improve the performance of dielectric materials in capacitors is still a promising research. This paper chooses the ferroelectric polymer poly(vinylidene fluoride) (PVDF) that worked as the matrix, and the linear polymers polyimide, cyanoethyl pullulan (CR-S), polyethersulfone, and cyanoethylated cellulose served as fillers. This all-organic dielectric composite produced as films working in electrostatic energy storage devices is prepared by using a casting method. Analyzing the test results, the composite film exhibited excellent electrical properties when the CR-S doping content was 5 wt. %. The organic composite dielectric based on CR-S/PVDF has a breakdown field strength of 450 MV/m, a discharge energy storage density (Ue) of 10.3 J/cm3, a high dielectric constant of 10.9, and a low dielectric loss of 0.004 at 1 kHz, which is a significant improvement compared with other dielectric composites. This all-organic dielectric composite strategy offers a new approach to achieve better-performance dielectric energy storage materials.