Reduced conductivity in sandwich-structured BFT@DA/PVDF flexible nanocomposites for high energy storage density in lower electric field

The Ba(Fe_(0.5)Ta_(0.5))O_(3)@DA/PVDF flexible composite films with sandwich-structured are prepared by solution-casting method.According to SEM image,the thickness of the composite film is about 15 mm and the each layer is about 5 mm.The sandwich-structured nanocomposite films not only have higher permittivity but also lower AC conductivity.The high permittivity is due to the large permittivity of BFT and the enhanced interface polarization between ceramic particles and polymer matrix.The low AC conductivity is due to the absence of conductive pathways in the PVDF layer.At low electric field strength of 150 MV/m,the energy density of sandwich-structure composite films filled with 1 vol% is 1.93 J/cm^(3).When the breakdown strength is 250 MV/m,the maximum energy storage density is increased to 4.87 J/cm^(3).The sandwich-structure Ba(Fe_(0.5)Ta_(0.5))O_(3)@DA/PVDF flexible composite films with outstanding energy storage properties in lower electric field can be used for wearable devices in the future.

Improved thermal conductivity and breakdown strength of PVDF-based composites by improving the dispersion of BN

In order to adapt to the development of electronic devices,it is necessary to improve the thermal conductivity and breakdown strength of composites.Boron nitride(BN)is an ideal candidate material with high breakdown strength and thermal conductivity.There-fore,the introduction of BN nanosheets into the polyvinylidene fluoride(PVDF)matrix can improve the thermal conductivity and breakdown strength of the composites at the same time.However,BN nanosheets can easily agglomerate in the matrix,which limits the improvement of the properties of the composites.To overcome this difficulty,appropriate water-bath heating was used to improve the fluidity of PVDF.Therefore,the dispersion of the filler is improved.When the volume fraction of BN nanosheets is 3%and the preparation temperature is 45℃,the energy storage density of the compos-ites reached 18.5 J/cm^(3) at 540 kV/mm.At this point,the thermal conductivity was 0.49 W/(m⋅K),3.5 times that of the pure PVDF film.