Ni(OH)2 as an novel shell layer material for core-shell dielectric filler based on barium titanate and their dielectric polymer composites in P(VDF-HFP) matrix

Abstract Dielectric capacitors with high dielectric constant and energy density are of great importance for electronic devices. Barium titanate(BaTiO3) have been widely explored for polymer-based dielectric composites owning to its ultrahigh dielectric constant and commercial availability. However, due to the large difference of dielectric constant between BaTiO3 and polymer matrix, the interface becomes fragile under electric field, which is not conducive for the improvement in breakdown strength and energy storage density. Herein, a flower like barium titanate/nickel hydroxide(BTO/Ni(OH)2) core-shell structured filler has been fabricated to provide a novel approach to modify the interface between BTO and P(VDF-HFP) matrix for dielectric polymer composites. Ni(OH)2 nanoflakes have grown in-situ on the surface of hydroxylated BaTiO3 particles to form the flower like core-shell assemblies via hydrothermal reaction. Then, these synthetic BTO/Ni(OH)2 particles with specific flower-like core-shell structure can be uniformly dispersed in P(VDF-HFP) without any additional surface modification due to their surface –OH groups. Meanwhile, Ni(OH)2 shell triggered beta phase of P(VDF-HFP) near core-shell filler based on the interfacial interaction between Ni(OH)2 and P(VDF-HFP). Thus, the intensity of the local electric field can be gradually reduced due to the formation of a dielectric constant gradient. Besides, these Ni(OH)2 nanoflakes shell are able to cut down the local electric field and prevent the growth of electrical trees on the surface of BaTiO3 during breakdown process. When the composite filler content is 10 wt%, the dielectric constant and breakdown strength increases to 14.8 and 330 kV/mm from 11 to 260 kV/mm, respectively. And the calculated energy density is 7.13 J/cm3, which is 1.5 times that of 10 wt% BTO/P(VDF-HFP) composite film. This study provides a novel shell material Ni(OH)2 for the preparation of BTO core-shell structure filler, which has good compatibility with polymer substrates.