Enhanced High‐Temperature Energy Storage Properties of BOPP Capacitor Films by Coating Heterostructural Ceramics Layers

ABSTRACT Biaxially oriented polypropylene (BOPP), the dielectric material of choice for polymer film capacitors, is widely used in advanced electronic devices and power grids, among other applications. However, the nonlinear growth of the conduction loss at high temperatures leads to a rapid deterioration of its energy storage performance, which seriously hinders the development trend of miniaturisation and high integration of power systems. In this study, inorganic nanolayers with heterogeneous structure were grown on the surface of BOPP films by magnetron sputtering using high dielectric constant BaZrTiO 3 and wide bandgap Al 2 O 3 ceramic targets. Experimental and theoretical analyses show that the use of wide bandgap Al 2 O 3 as the heterojunction outer layer can effectively impede carrier injection and transport, leading to a significant reduction in the leakage current density of the composite film, effectively enhancing the high temperature energy storage performance of the composite films. The synergistic enhancement of the inorganic heterojunction structure on the dielectric properties and insulating strength of the polymer film is attributed to the ability of the Al 2 O 3 /BaZrTiO 3 /BOPP/BaZrTiO 3 /Al 2 O 3 (O‐B‐P‐B‐O) composite films to exhibit a discharge energy density of 2.49 J/cm 3 and a charge/discharge efficiency of 77.6% at 125°C and 500 MV/m.