Polyhydroxy organic molecule-cross-linked polyvinylidene fluoride with enhanced breakdown strength and energy density

Abstract

Polyvinylidene fluoride (PVDF) has been extensively studied for dielectric energy storage applications owing to its excellent dielectric properties. There remains a persistent demand to enhance its breakdown strength and achieve higher energy storage density. In this work, a hydrogen-bonding cross-linking strategy is demonstrated to effectively enhance the breakdown strength and energy storage performance of PVDF. Tris(hydroxymethyl)nitromethane (THNM), containing multiple hydroxyl groups, was employed as a cross-linking agent to form multiple hydrogen bonds with the C–F groups in PVDF chains via a facile solution-casting process. The establishment of a hydrogen-bonding cross-linked network significantly enhances the mechanical strength and introduces charge traps into the PVDF matrix, thereby increasing the breakdown strength from 572 MV/m for the pristine PVDF film to 744 MV/m for the THNM-cross-linked-PVDF film (T-c-PVDF). Consequently, the T-c-PVDF film achieves a high energy storage density of 21.83 J/cm3, representing a 150% improvement over the pure PVDF film, while maintaining a charge–discharge efficiency exceeding 70%, and the energy storage performance stands out among PVDF-based dielectric materials from state-of-the-art works. This work highlights the significant potential of constructing a hydrogen-bonding cross-linked network within dielectric polymers in enhancing their breakdown strength and energy storage performance.