Epoxy/PVDF/Epoxy Composite Film with Concurrent Enhancement in Energy Density and Charge-discharge Efficiency

Abstract

Charge-discharge efficiency of more than 90% is a necessary condition for electrostatic capacitors with polymer dielectrics as storage media of electrical charges considering their practical application, how to achieve high energy storage density and high charge-discharge efficiency at the same time is now a research hotspot. Film capacitors generally work under electric field strength below 200 MV/m, at which the charge-discharge efficiency of less than 80% of polyvinylidene fluoride (PVDF) films limit their application in many cases. Herein, Epoxy/PVDF/Epoxy composite films in sandwich structure with different volume ratios of epoxy resin are prepared, cross section of which is characterized by SEM and EDS, expected energy storage properties would be both high energy storage density and high charge-discharge efficiency of 95% under electric field strength below 200 MV/m. Dielectric spectrum and energy storage properties have been tested. The trilayered composite films with varied volume ratios of epoxy resin are capable of operating with equivalent level of charge-discharge efficiency (up to 96%) as biaxially oriented polypropylene (BOPP) films and concurrently delivering energy storage density (1.6 J • cm−3) which indicates an 300% enhancement over the commercial used BOPP films under electric field strength of 200 MV/m, this work provides preliminary proof of a means of using crosslinked epoxy resin to improve charge-discharge efficiency of PVDF.