The ultrahigh discharge efficiency and energy density of P(VDF-HFP) via electrospinning-hot press with St-MMA copolymer

Abstract

Poly(vinylidene fluoride) (PVDF) based fluoropolymers possess high permittivity and breakdown strength (E_b), and have been extensively studied because of their dielectric applications. However, their practical applications are greatly hampered by the low energy density (U_e) and efficiency (η). Herein, using an electrospinning-hot press strategy, a novel P(VDF-HFP)/MS (poly(vinylidene fluoride-hexafluoropropylene)/poly(methyl methacrylate-co-styrene)) composite film with concomitantly enhanced U_e of 20 J cm⁻³ and discharge efficiency (η ≈ 81%) was fabricated. Due to the strong electrostatic force and confining effect during electrospinning, two polymers exhibit substantially enhanced compatibility and form a much more homogeneous microstructure as compared with the blend control, leading to higher E_b and more even electric field distribution as simulated by the finite element analysis. Strikingly, composite films containing 30 wt% MS copolymer exhibit typical relaxor polarization behaviors (and thus improved E_b and U_e), which are 157% and 262% that of the pristine P(VDF-HFP), respectively. Moreover, the η of composite films can be well retained, even if it is under a high E_b of 550 MV m⁻¹, and is still greater than previous reported values. This work provides a straightforward and scalable strategy to achieve PVDF-based dielectrics with both high U_e and η for the applications of energy storage capacitors.