Hot‐Stretching of Barium Titanate and Poly(Arylene Ether Nitrile) Composites for Enhanced Energy Storage Density

ABSTRACT High‐performance dielectric polymer composites are essential for advancing energy storage technologies. However, the energy storage capability of polymer dielectric composites remains restricted due to the challenge of concurrently increasing both dielectric permittivity and breakdown strength. Herein, we demonstrate improved energy storage performance in hot‐stretched composites comprising poly(arylene ether nitrile) (PEN) and sulfonated poly(arylene ether nitrile) (SPEN)‐functionalized barium titanate nanoparticles (BTNP) (SPEN@BTNP). Due to the similar main‐chain structure of SPEN to PEN, SPEN@BTNP is well dispersed in the PEN matrix. As a result, an enhanced dielectric constant of 6.60 at 10 3 Hz and an energy storage density of 1.07 J‧cm −3 with a filler content of 20 wt% are observed. Upon uniaxial hot‐stretching, both the permittivity and breakdown strength of these composites are further enhanced. Specially, at 20 wt% of filler content, the hot‐stretched composite exhibits a dielectric constant of 7.04 and a breakdown strength of 198.1 kV/mm. Therefore, an energy density of 1.22 J‧cm −3 , which is 50% higher than that of pristine PEN (0.82 J‧cm −3 ), is obtained for this hot‐stretched composite. The improved energy density of these PEN composites demonstrates that uniaxial hot‐stretching is an effective way for enhancing the energy density of dielectric polymer composites.