Adding additives is the most convenient and effective way to induce polar poly(vinylidene fluoride) (PVDF) crystals which exhibit excellent ferroelectronic, piezoelectric, and dielectric properties. In this work, a kind of environmentally friendly additive, deep eutectic solvent (DES), is introduced to induce the crystallization of polar phases and accelerate the α‐to‐γ phase transition, which enables the fraction of γ(γ′)‐phase crystals to exceed 90% in the PVDF/DES composite containing only 1 wt% DES. The ion–dipole interaction between PVDF and hydrogen bond acceptor in DES induces the polar molecular conformation, thus bringing about the formation of polar phase crystals. However, hydrogen bond donor promotes the dispersion of hydrogen bond acceptor in PVDF matrix, contributing to the flexibility of the composites.

The high dielectric constant of PVDF is very important for its high-performance energy storage dielectrics, but it is more critical to strike a proper balance between high dielectric constant and low dielectric loss. In this work, deep eutectic solvent (DES) and montmorillonite (MMT) have been used together to prepare γ-phase PVDF composite films with excellent dielectric properties. It is found that DES significantly induces crystallization of γ-phase and increases the dielectric constant of the composite due to the incremental ion motion. Meanwhile, DES greatly promotes the stripping and dispersion of MMT layers, which in turn inhibits the long-range ion migration and therefore suppresses the dielectric loss of the composite to a very low level. The dielectric constant of PVDF/MMT/DES composite films can increase to 32, while the dielectric loss remains as low as 0.06 at 1 kHz. Moreover, the synergistic effect of MMT/DES also contributes to enhancing the toughness and optical transmittance of composite films.