High Dielectric Constant Polycarbonate/Nylon Multilayer Films Capacitors with Self-Healing Capability

Abstract

With the fast development of high-temperature metal oxide semiconductor field effect transistors for power electronics in electric vehicles, current state-of-the-art biaxially oriented polypropylene (BOPP) film capacitors need further improvement because they have a temperature rating of only 85 °C without derating the voltage to maintain a long lifetime. If a high-temperature polymer can replace BOPP without sacrificing the overall dielectric performance and cost, it is possible to remove the current water-cooling system for capacitors and significantly reduce the cost of the power electronic unit. In this work, we demonstrated new polycarbonate (PC)/nylon multilayer films (MLFs), which has a potential for even higher temperature rating because of the higher melting temperature for nylons (e.g., nylon-6). Structural and dielectric studies showed that these PC/nylon MLFs had a similar dielectric performance, such as dielectric constant, dielectric loss, and breakdown strength, as the PC/poly(vinylidene fluoride) PVDF MLFs, which were developed in the past. These PC/nylon MLFs could perform well up to 120 °C, which was limited by the glass transition temperature of PC at 145 °C. More intriguingly, packaged PC/nylon-12 MLF capacitors exhibited a self-healing capability, which had been difficult for packaged high-temperature film capacitors. Because self-healing is such a fundamental requirement for polymer film capacitors, our PC/nylon MLFs offer a potential for next-generation high-temperature and high-energy density film capacitors.