Achieving Superior Energy Storage Performance for All-Organic Pvdf/Mg Crosslinked Composite Dielectric Films Through the Cooperation of Crosslinking and Hydrogen Bonding Networks

Abstract

Poly(vinylidene fluoride) (PVDF) based polymer dielectrics showcase great value and prospects for energy storage applications by reason of their excellent dielectric properties. Nevertheless, the high loss of PVDF itself results in low discharge efficiency, which inevitably generates Joule heat, and leads to low breakdown strength (Eb). In order to overcome these problems, abundant studies have been conducted on the fact that the introduction of linear dielectrics into PVDF polymers can effectively suppress its loss and confer a high Eb. To further enhance the energy storage performance of the composites, in this contribution, poly(vinylidene fluoride)/methyl methacrylate-co-glycidyl methacrylate (PVDF/MG) composite was used as the matrix, small molecule 2,5-dihydroxyterephthalic acid (DHTA) was chosen as the crosslinking agent to form the crosslinking network with MG, so the novel all-organic crosslinked composite dielectric films were prepared by chemical crosslinking and multiple hydrogen bonding network. The MG crosslinked network and extra hydrogen bonding interactions can effectively restrain dielectric loss (tanδ) and improve the Eb of PVDF/MG to endow crosslinked composites with higher discharged energy density (Ue), and efficiency. For all-organic crosslinked composites, the optimal Ue of 24.4 J/cm3 along with the discharge efficiency of ~73% was achieved under 640 MV/m as the content of DHTA reached 1%, which was nearly 2.4 times higher than that of the pristine PVDF/MG composite film. The enhancement of energy storage performance is attributed to the fact that cross-linking points and hydrogen bonds can act as charge deep traps, which can capture carriers and boost the Eb by the theoretical and experimental results. In this research, the design of novel all-organic crosslinked structures provides a new strategy for obtaining dielectric materials with high Ue.

Keywords: Energy density, Crosslinking, hydrogen bond, dielectric, breakdown strength