Biaxially oriented polypropylene (BOPP) is one of the most commonly used commercial capacitor films, but its upper operating temperature is below 105 °C due to the sharply increased electrical conduction loss at high temperature. In this study, growing an inorganic nanoscale coating layer onto the BOPP film's surface is proposed to suppress electrical conduction loss at high temperature, as well as increase its upper operating temperature. Four kinds of inorganic coating layers that have different energy band structure and dielectric property are grown onto the both surface of BOPP films, respectively. The effect of inorganic coating layer on the high‐temperature energy storage performance has been systematically investigated. The favorable coating layer materials and appropriate thickness enable the BOPP films to have a significant improvement in high‐temperature energy storage performance. Specifically, when the aluminum nitride (AlN) acts as a coating layer, the AlN‐BOPP‐AlN sandwich‐structured films possess a discharged energy density of 1.5 J cm⁻³ with an efficiency of 90% at 125 °C, accompanying an outstandingly cyclic property. Both the discharged energy density and operation temperature are significantly enhanced, indicating that this efficient and facile method provides an important reference to improve the high‐temperature energy storage performance of polymer‐based dielectric films.

Polymer-based dielectric composites have become a hot topic in recent years due to their high-power density and high breakdown strength. However, some disadvantages still exist in some typical monopolymers, which are not conductive to improving the energy storage performances significantly, such as high energy loss of PVDF and low polarization of PMMA. Based on the good compatibility of PMMA and PVDF, this paper proposes a binary polymer blending strategy to improve the polarization and energy storage properties of the dielectric composite. The influences of volume content of PMMA in PVDF and heat treatment temperature during the fabrication process on the microstructure, polarization behaviors and energy storage performances of the PMMA blended PVDF composites (abbreviated as PMMA/PVDF) are systematically investigated. Fortunately, when the heat treatment temperature was 150 °C, the binary blending composite of PMMA/PVDF with a PMMA content of 50 vol% possessed an excellent storage density of 20.1 J cm⁻³ at 570 kV mm⁻¹, and an energy storage efficiency of 63.5%. This study provides an effective method for designing polymer materials with excellent energy storage properties.

As a key component of the dielectric capacitor, the dielectric material directly determines the performance of the capacitor. Poly(vinylidene fluoride) (PVDF) has received extensive attention for its large dielectric constant. However, PVDF has poor temperature resistance and cannot be used in high-temperature areas. In this work, a symmetrical sandwich structure was prepared by compounding polycarbonate (PC) and PVDF, in which PC has higher insulation and heat resistance than PVDF. It was found that as the temperature increases, the applied electric field would gradually concentrate on the PC layer, while the electric field borne by the PVDF layer gets much lower. In this way, a similarity-intelligent dielectric with the performance of self-adjusting electric field distribution was obtained, which can effectively avoid premature breakdown of PVDF under high-temperature conditions. Besides, when the PC is on the outside (CFC), it can not only increase the difficulty of carrier injection at the electrode, but also improve the heat resistance of the composite dielectric, and interface charge generated by this structure can effectively trap the carriers injected at the electrode. Finally, CFC-2 has excellent temperature stability and energy storage performance; it can withstand a breakdown strength of 500 MV m⁻¹ even at 100 °C, and its energy storage density (6.35 J cm⁻³) and charge–discharge efficiency (77.21%) are 93.52% and 91.31% of room temperature, respectively. This work effectively improves the high-temperature energy storage characteristics of PVDF and broadens its application fields. Thus, improving the high-temperature energy storage characteristics of polymer dielectrics is of great significance.

Optimizing the high‐temperature energy storage characteristics of energy storage dielectrics is of great significance for the development of pulsed power devices and power control systems. Selecting a polymer with a higher glass transition temperature (T_g) as the matrix is one of the effective ways to increase the upper limit of the polymer operating temperature. However, current high‐T_g polymers have limitations, and it is difficult to meet the demand for high‐temperature energy storage dielectrics with only one polymer. For example, polyetherimide has high‐energy storage efficiency, but low breakdown strength at high temperatures. Polyimide has high corona resistance, but low high‐temperature energy storage efficiency. In this work, combining the advantages of two polymer, a novel high‐T_g polymer fiber‐reinforced microstructure is designed. Polyimide is designed as extremely fine fibers distributed in the composite dielectric, which will facilitate the reduction of high‐temperature conductivity loss for polyimide. At the same time, due to the high‐temperature resistance and corona resistance of polyimide, the high‐temperature breakdown strength of the composite dielectric is enhanced. After the polyimide content with the best high‐temperature energy storage characteristics is determined, molecular semiconductors (ITIC) are blended into the polyimide fibers to further improve the high‐temperature efficiency. Ultimately, excellent high‐temperature energy storage properties are obtained. The 0.25 vol% ITIC‐polyimide/polyetherimide composite exhibits high‐energy density and high discharge efficiency at 150 °C (2.9 J cm⁻³, 90%) and 180 °C (2.16 J cm⁻³, 90%). This work provides a scalable design idea for high‐performance all‐organic high‐temperature energy storage dielectrics.