A simple surface engineering approach to enhance the Schottky barrier of polymer dielectrics for superior energy storage performance

To address the escalating demands for energy storage and conversion in harsh environments, polymer dielectrics, which are critical in electrostatic capacitors, must function effectively under high electric fields and at elevated temperatures. However, low discharge energy density (U_d) and performance degradation at elevated temperatures present significant barriers to further application and development of polymer dielectrics. This paper describes a simple method to improve the high-temperature breakdown strength (E_b) and energy storage performance (ESP) of a polyethylene terephthalate (PET) film. A wide bandgap SiO₂ inorganic nanolayer is deposited onto the PET surface using a one-step immersion coating process. The wide bandgap layer effectively reduces the charge injected into the polymer dielectric and conductivity of the dielectric surface. At 25 °C, coated films exhibit significant E_b (∼728.4 MV m⁻¹) and high U_d (∼9.1 J cm⁻³), along with excellent charge-discharge efficiency (η) (∼88.9%). At 125 °C, the E_b of PET improves significantly from 509.8 MV m⁻¹ to 623.3 MV m⁻¹, with a corresponding maximum U_d of 6.6 J cm⁻³. This work introduces a practical and efficient interface design strategy for high-temperature polymer dielectric materials.