Achieving superior energy density in ferroelectric P(VDF-HFP) through the employment of dopamine-modified MOFs

Dielectric polymer/composites films with excellent capacitive performance has initiated enormous interest from both academic and industry because of their great potential as flexible and light-weight electrostatic capacitors for modern electric and electronic systems. In this work, we report a novel flexible dielectric composite film consisting of poly (vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) and dopamine-modified metal-organic frameworks Co3 [Co(CN)6]2 (D-M) with excellent capacitive performance for energy storage application. It is found that the D-M show good compatibility with P(VDF-HFP), permitting a high breakdown strength for composites. Meanwhile, the large specific surface area and special porous three-dimensional nanostructure of D-M also has the effect of raising dielectric performance while eliminating the inherent ferroelectric loss of P(VDF-HFP), resulting in considerably promoted discharge energy density. Furthermore, D-M is found to favor the formation of γ-phase in P(VDF-HFP), which is also advantageous to raise the discharge energy density. Upon a small loading of 0.6 wt% D-M, the composites perform a maximum discharge energy density of 11.89 J/cm3 and discharge efficiency of 71.28% at 350 MV/m, which are 3.04 times and 1.25 times those of the pure P(VDF-HFP) film, respectively. For the first time, we demonstrate that the applicability of flexible D-M/P(VDF-HFP) dielectric composites as advanced electrostatic capacitors, providing a new sight for the design of dielectrics with high capacitive performance.