Appreciable amelioration in the dielectric and energy storage behavior of the electrospun fluoropolymer PVDF-HFP thick films: Effect of hot-pressing

Abstract

Prospects of applicability of electrospun Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) films for high energy density capacitors operable under harsh conditions (30 °C - 80 °C) has been investigated. The dielectric and energy storage behavior of structurally and morphologically characterized electrospun hot-pressed PVDF-HFP film has been thoroughly studied and analyzed in the temperature range of 30 °C - 80 °C. The pristine film, film hot-pressed at 110 °C and 150 °C are nominated as H-0, H-110 and H-150. The dielectric constant (ε) and dielectric loss (tanδ) of H-150 film at 1 kHz is found to be ∼13.4 and ∼ 0.04 respectively; whereas the respective values for H-110 films are ∼9.8 and ∼ 0.08. The dielectric properties of H-150 film are relatively more thermally stable as compared to H-110 film up to 80 °C. Discharge energy density, energy efficiency and breakdown strength for H-150 film are 3.7 J/cm³, 56 % and 1189 kV/cm respectively, which is remarkably higher as compared to H-0 with respective values as 0.128 J/cm³, 20 % and 352 kV/cm and H-110 film with respective values as 0.598 J/cm³, 42 % and 771 kV/cm. The superior dielectric properties, breakdown strength and energy storage behavior of PVDF-HFP film hot-pressed at 150 °C is attributed to the formation of a micro capacitive network caused by interfacial connectivity and alignment of the nanofibers. Hot-pressing of nanofiber polymeric films is a simple yet effective technique that could be a futuristic approach to develop dielectric films for high energy density capacitors.