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

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.