Sandwich‐structured dielectrics constructed from carbon nanotube and polyarylene ether nitrile composite layers demonstrating positive and negative permittivity.

Highlights Polymeric dielectric materials with high energy storage density have attracted plenty of attention due to their broad application prospects in electronic device fields. However, energy density of polymer dielectrics is limited originating from the difficulty in balancing permittivity and breakdown strength. Herein, we report fabrication of sandwich‐structured polyarylene ether nitrile (PEN) composites with enhanced energy density by hot pressing single layered phthalonitrile groups modified carbon nanotube (Ph‐CNT) and PEN (Ph‐CNT/PEN) composite films demonstrating positive and negative permittivity. The Ph‐CNT/PEN composites exhibit positive permittivity at Ph‐CNT content lower than 6 wt%, while shows negative permittivity at a higher Ph‐CNT concentration. Attributing to the synergistic action of the positive and negative dielectric layer, the dielectric constant is enhanced to 90.9 at 200 kHz for sandwich‐structured PEN composite T‐6‐8‐6 at a thickness ratio of 1/0.5/1. Although the breakdown strength is decreased to 147.7 kV/mm, the 1/0.5/1 sandwich‐structured film T‐6‐8‐6 demonstrates an energy storage as high as 9.1 J/cm3, which is about 10 times to that of pure PEN. This boosted energy storage density presents a fresh approach to advancing high‐performance dielectric materials, offering wide‐ranging potential applications across electronic devices. Sandwich‐structured PEN composites with enhanced energy density are fabricated. Sandwich‐structured films consists of positive and negative dielectric layer. Ph‐CNT/PEN exhibit negative permittivity at a higher Ph‐CNT concentration. Dielectric constant increases due to synergistic action of dielectric layers. Sandwich‐structured film demonstrates an energy storage as high as 9.1 J/cm3. [ABSTRACT FROM AUTHOR]