Energy Storage and Mechanical Performance of PVDF-HFP/SWCNT Composites with Low Permeability

Polymer dielectric capacitors, with their high energy storage density and fast release of energy, have recently received increasing attention for their ability to meet the critical requirements of pulsed power devices in low-consumption systems. In this context, this paper reports that surface-modified single-walled carbon nanotubes (SWCNT) were successfully synthesized and used as fillers to improve the energy storage and mechanical performance of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based composites. The PVDF-HFP/SWCNT composites realize high dielectric constants and low percolation thresholds of 62 and 0.25, respectively. In particular, when composites possess an SWCNT content of only 0.4 vol.%, an acceptable energy storage density of 0.24 J/cm 3 at a low electric field of 700 kV/cm along with a high energy storage efficiency (74%) is also observed. Meanwhile, the tensile strength and breaking elongation are 44 MPa and 8.1%, respectively. According to detailed characterization results, SWCNT with low filling are uniformly dispersed and show a certain orientation in PVDF-HFP after surface modification, which is the key to improve the composite performance. These results provide an effective method for fabricating flexible-polymer composites with a high density of energy storage.