Flexible BaTiO3/PVDF gradated multilayer nanocomposite film with enhanced dielectric strength and high energy density

Organic-inorganic 0-3 nanocomposites, which combine the potentially high dielectric strength of the organic matrix and the high dielectric permittivity of the inorganic filler, are extensively studied as energy-storage dielectrics in high-performance capacitors. In this study, a gradated multilayer BaTiO3/poly(vinylidene fluoride) thin film structure is presented as a means to achieve both a higher breakdown strength and a superior energy-storage capability. The central layer of this film, designed to provide high electric displacement, is composed of a high volume fraction of 6-10 nm BTO nanocrystals produced by a TEG-sol method. The small particle size contributes to a high dispersibility of the nanocrystals in polymer media, as well as a high interfacial area to mitigate the local electric field concentration. The outer layers of the structure are predominantly PVDF, with a significantly low volume fraction of BTO, taking advantage of the high dielectric strength of pure PVDF at the electrode-nanocomposite interface. The film is mechanically flexible, and can be removed from the substrate, with total thicknesses in the range of 1.2-1.5 mm. Parallel plate capacitance devices exhibit highly improved dielectric performances with low-frequency permittivity values of 20-25, a maximal discharge energy density of 19.37 J cm(-3) and dielectric (breakdown) strengths of up to 495 kV mm(-1).