Highly Transparent PVDF Films with Enhanced Dielectric and Energy Storage Properties Tailored by a PMMA-co-GMA Copolymer

High losses and low efficiency have been the main defects limiting poly(vinylidene fluoride) (PVDF) as an energy storage film capacitor material. Herein, the linear methyl methacrylate-co-glycidyl methacrylate (MG) copolymer was prepared to improve the dielectric and energy storage performance of PVDF. FTIR spectroscopy and XRD results showed that the introduction of MG induced the crystal phase transformation of PVDF. Polarized optical microscopy and DSC tests proved the smaller crystal size and lower crystallinity of PVDF in the composites. The introduction of MG decreased the permittivity of PVDF and suppressed dielectric and conductive losses. The composites showed higher breakdown strength, which increased from 300 MV/m for PVDF to 540 MV/m for the PVDF/MG-40% composite. Despite the weak polarity of MG, the complementary breakdown strength endowed excellent discharge energy density and efficiency for the PVDF/MG composites. The discharge energy density increased from 3.75 J/cm3 for PVDF to 9.2 J/cm3 for the PVDF/MG-40% composite. Meanwhile, the PVDF/MG-40% composite still maintained a high efficiency of 84% even at a 540 MV/m electric field. This research provides a feasible design idea for all-organic composite membranes. More importantly, the reactive activity of epoxy groups on the MG copolymer can be utilized for later performance optimization of PVDF/MG dielectric membrane through regulation strategies.