Dielectric Performance Improvement of Polypropylene Film by Constructing Charge Injection Suppression Layers

In this paper, terephthalaldehyde/PP layer and parylene/PP layer are introduced into the membrane near the anode side and cathode side for improving the dielectric properties of polypropylene (PP) films. The results indicate that the composite film with 0.02 wt% terephthalaldehyde and 0.015 wt% parylene in the corresponding functional layer exhibits best. The leakage conductivity declines by 94% at 30 °C and decreases by 98% at 125 °C. The charge accumulation rate K drops from 1.74 to 1.05 at 30 °C and decreases from 2.48 to 1.28 at 125 °C. The DC breakdown strength is improved by 26%-32%, and the discharged energy density is enhanced by 89%-101%. The introduction of the functional layers will trigger charge trapping effect and form a reverse electric field near the electrode, thereby suppressing the charge injection. This method provides a reference for obtaining films with better insulation performance and energy storage characteristics from the perspective of charge transport.