Partially unzipped carbon nanotubes-CaCu₃Ti₄O₁₂ /ferroelectric polymer nanodielectric composites with high permittivity, high energy storage capacity and low dielectric loss

Carbon nanotubes (CNTs) due to their outstanding features, such as unique electronic properties and large specific surface areas, have been intensively studied as nanoscale fillers to improve the permittivity of polymer dielectrics. However, due to the unfavourable formation of conductive channels, these CNTs-derived nanocomposites usually suffer from high dielectric loss and low breakdown strength, therefore greatly restricting their practical applications. In this work, we modified pristine multiwalled carbon nanotubes (MWCNTs) by chemical oxidation to prepare partially unzipped carbon nanotubes (PUCNTs), which not only retained excellent electrical properties but also enhanced inter- facial interactions with polymers. The obtained PUCNTs/poly(vinylidene fluoride) (PVDF) nanocomposites exhibit higher permittivity and lower dielectric loss compared to raw MWCNTs added. To further alleviate the detrimental influence of conductive channels, we have designed a new class of hybrid composed of PUCNTs-decorated CaCu₃Ti₄O₁₂ nanoparticles (PUCNTs-CCTO) and their PVDF-based nanocomposites. At 1 kHz, the PUCNTs-CCTO/PVDF nanocomposite filled the ternary nanocomposites also possess strong resistance to electric field failure and achieve significantly enhanced energy storage capability. With 3 vol% PUCNTs and 30 vol% CCTO, the breakdown strength of the nanocomposite can still be maintained at 125 kV mm^-1 and the theoretical maximum energy density reaches to 15.5 J cm^-3, which is nearly 3 times compared to neat PVDF (5.1 J cm^-3). These merits of the PUCNTs-CCTO/PVDF nanocomposites suggest that the strategy proposed herein is a promising avenue for the development of dielectric materials with high energy storage capacity. (author)