Dielectric Properties’ Synergy of Stretched P(VDF-HFP) and P(VDF-HFP)/PMMA Blends Creates Ultrahigh Capacitive Energy Density in All-Organic Dielectric Films

Dielectric capacitors with a high energy-storage density and efficiency are urgently required for miniaturization and integration of power electronics and pulsed power system. Herein, single-layered stretched P(VDF-HFP) with a certain content of poly(methyl methacrylate) (PMMA) and two kinds of sandwich-structured films are prepared to optimize and compare energy-storage performance. The results revealed that the crystallization transition behavior of stretched P(VDF-HFP) films contributed to enhance its electric polarization, while the introduction of linear type PMMA resulted in an enhancement of voltage tolerance of stretched films by improving the mechanical properties and suppressing leakage current. What’s more, the effects of crystalline orientations and structure design on the breakdown mechanism of stretched films were revealed by finite element theoretical simulation. As a consequence, the stretched sandwich-structured 0-25-0-S (pure P(VDF-HFP) serves as the outer layer, and blends represent the middle layer; the digit representing PMMA content in the P(VDF-HFP)) displayed a high Ue of 28.71 J/cm3 and η of 74% under 680 MV/m. This work provides a workable and effective method for developing capacitive films with great energy-storage performance.