In recent years, PbZrO₃ (PZO) films have become favorable electric storage materials due to the unique electric field-induced phase transition behavior, but the severe hysteresis effect leads to low energy storage density and efficiency. In this work, inserting Al₂O₃ (AO) insulation nanolayers is proposed to tune the polarization behavior of flexible PZO films, anticipating optimization of energy storage performance. The results show that the thickness of the AO nanolayers has a deep influence on the polarization behavior of the PZO films, and PZO/AO/PZO (PAP) sandwiched films with 8 nm AO interlayer deliver relaxor ferroelectric-like polarization instead of antiferroelectric counterpart. To further utilize the AO nanolayers as top/bottom layers, the linear-like polarization and the highest breakdown strength are achieved in the AO/PZO/AO/PZO/AO (APAPA8) multilayer films, leading to both high discharged energy storage density of 35.2 J/cm³ and efficiency of 92.9%, as well as excellent fatigue and bending endurance, good temperatures, and frequency stability. The tunable polarization induced by growing the AO nanolayers makes antiferroelectric PZO films have great potential to be used as energy storage dielectrics.

Biaxially oriented polypropylene (BOPP) is one of the most commonly used commercial capacitor films, but its upper operating temperature is below 105 ℃ 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 ℃, 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.

Commercial biaxially oriented polypropylene (BOPP) film capacitors have been widely applied in the fields of electrical and electronic engineering. However, due to the sharp increase in electrical conduction loss as the temperature rises, the energy storage performance of BOPP films seriously degrades at elevated temperatures. In this study, the grafting modification method is facile and suitable for large-scale industrial manufacturing and has been proposed to increase the high-temperature energy storage performance of commercial BOPP films for the first time. Specifically, acrylic acid (AA) as a polar organic molecular is used to graft onto the surface of commercial BOPP films by using ultraviolet irradiation (abbreviated as BOPP−AA). The results demonstrate that the AA grafting modification not only slightly increases the dielectric constant, but also significantly reduces the leakage current density at high-temperature, greatly improving the high-temperature energy storage performance. The modified BOPP−AA films display a discharged energy density of 1.32 J/cm³ with an efficiency of >90% at 370 kV/mm and 125 °C, which is 474% higher than that of the pristine BOPP films. This work manifests that utilizing ultraviolet grafting modification is a very efficient way to improve the high-temperature energy storage performance of commercial BOPP films as well as provides a hitherto unexplored opportunity for large-scalable production applications.