Orientating carbon nanotube bundles and barium titanate nanofibers in tri-layer structure to develop high energy density epoxy resin composites with greatly improved dielectric constant and breakdown strength

Abstract

Developing a high dielectric constant (high-k) composite with high breakdown strength and big energy density is still an interesting challenge with great difficulty. Herein, a new type of tri-layer composite (A-B-A) with greatly increased dielectric constant, breakdown strength and energy density was reported. The orientation of functional fillers as well as the thickness ratio of layer A to layer B in A-B-A composites were systematically investigated and correlated to dielectric properties, breakdown strengths and storage densities of multi-layer composites. With the same composition, A-B-A composites have much better integrated dielectric properties than single-layer (ACB/PDA@BTnf/EP) composite. For example, when the volume fraction of layer B is 20 vol%, the resulting tri-layer composite (A-2B-A) has the highest dielectric constant (1080.9, 100 Hz) and biggest increase in breakdown strength (150%) among all high-k multi-layer composites reported so far. In addition, A-2B-A composite has very low dielectric loss (0.55, 100 Hz) and 17.8 times increase in energy density compared with that of ACB/PDA@BTnf/EP. This contribution proposes an efficient and promising method to prepare high-k composites for energy storage.