Overviews of dielectric energy storage materials and methods to improve energy storage density

Due to high power density, fast charge/discharge speed, and high reliability, dielectric capacitors are widely used in pulsed power systems and power electronic systems. However, compared with other energy storage devices such as batteries and supercapacitors, the energy storage density of dielectric capacitors is low, which results in the huge system volume when applied in pulse systems. Therefore, to meet the needs of device miniaturization and integration, reducing the system volume and increasing the energy storage density have become very key research hot spots in the dielectric energy storage fields. In this paper, we first introduce the research background of dielectric energy storage capacitors and the evaluation parameters of energy storage performance. Then, the research status of ceramics, thin films, organic polymers, and organic–inorganic nanocomposites for energy storage is summarized. Next, the methods of improving the energy storage density of dielectric capacitors are concluded. For ceramic blocks and films, methods, such as element doping, multi-phase solid solution/coexistence structure, “core–shell” structure/laminated structure, and other interface adjustments, are effective to increase the energy storage density. While for organic–inorganic nanocomposites, the energy storage performance can be optimized by the surface modification and distribution of fillers, and multi-layer structure design. Finally, the future development tendency of the energy storage materials is prospected to consolidate the research foundation of dielectric energy storage and provide certain guidance value for their practical applications.