A superior nanolaminate dielectric barrier coating for high breakdown strength

Exfoliated montmorillonite nanosheets were self-assembled with poly(vinyl alcohol) on the surface of polymer films to form an organic/inorganic hybrid nanocoating. It was experimentally demonstrated that the highly oriented and aligned laminates of the nanocoating has a remarkable positive effect on the breakdown strength of the substrate polymer films including polyethylene, polystyrene and Kapton®. The improvement is attributed to the geometric confinement of the multilayer structure within the coating, which forms barriers to prevent the charge injecting into the polymer bulk and dissipate charge laterally. Pre-breakdown conduction measurement revealed that the coated polystyrene and Kapton films showed highly suppressed resistive current and higher inception field for charge injection compared with the blank films. Besides, biased-probe-induced charge injection into the film and the subsequent surface charge decay were investigated by Kelvin probe force microscopy, indicating a significantly suppressed charge injection in coated films which then dissipated away much faster. These barrier effects of the nanocoating provide a promising solution to increase the energy density of polymer capacitor films by increasing their breakdown strength without altering their intrinsic properties.