The Simultaneous Improvement of Energy Storage Density and Self-Healing Property of Metallized Film

In the present study, to improve the energy storage density and the self-healing property simultaneously, the double layer structure metalized film with the polyvinyl alcohol (PVA) coated on BOPP was proposed. With the increasing thickness of the PVA layer, the dielectric constant was raised, and the DC breakdown strength of the PP/PVA films first rising and then decreasing. Besides, the breakdown strength showed polarity dependence, and thus the highest breakdown strength 727.9 kV/mm was achieved with the PVA thickness of 2 μm, and the positive voltage applied on the PP side. The highest energy storage density of 5.97 J/cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> was obtained that was 63.56% higher than the neat PP film. Moreover, the self-healing energy and the equivalent conductivity decreased as the thickness of PVA went up, corresponding to the reduced capacitance loss and the suppressed temperature-rise of metalized film capacitor. The improvement of energy storage density and the self-healing properties were originated from the interface of PP and PVA layer and the optimized ingredients of the lower ratio of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{C}/(\mathbf{H}+\mathbf{O})$</tex>. The present study provides the new orientation for the development of dielectric material for metalized film capacitors.