To improve the dielectric performance
of polyvinylidene fluoride
(PVDF), BaTiO
3
/MWNTs/PVDF ternary composites were prepared
by the solution casting method. The percolation threshold (fraction
of MWNTs) has dropped greatly below 0.4 vol %, with the enhancement
of dielectric constant and breakdown field. For the BaTiO
3
/MWNTs/PVDF (11.5/0.35/88.15) composite, the dielectric constant
is 59, the loss is below 0.055, and the maximum operating electric
field is 324 MV/m, so the discharged energy density can be of up to
10.3 J/cm
3
with the efficiency of above 77.2%. The reason
of improvement was revealed by the scanning electron microscope images
and the X-ray diffraction data. It is found that uniform distribution
of filler in the composites and the increase of the β phase
of polymers result in the enhancement of polarization and improvement
of dielectric constant of PVDF. The third-phase spherical inorganic
particles prevent the formation of conductive networks and improve
the uniformity of local electric field, so the breakdown strength
of composites can be enhanced greatly. Here, this paper provides a
method to get the composites with high energy storage density for
supercapacitors.
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