Tuning aggregation state in PTMA/PVP blends for high energy storage

Abstract

Dielectric capacitors supported by all-organic materials show great potentials in advanced electronic and electric devices. However, the contradiction between increases in dielectric constant and breakdown strength severely prevents the development of high-performance all-organic materials. Here, simultaneous increases in dielectric constant and breakdown strength are achieved in the blend of poly(2,2,6,6-tetramethylpiperidinyloxy) (PTMA) and poly(N-vinyl-2-pyrrolidone) (PVP) by tuning the aggregation state. Given the film formability and polarity, PVP is blended into the high-dielectric constant PTMA as a binder to further improve the dielectric properties. An energy density of 8.6 J cm−3 is eventually obtained in the blend with 10% PVP loading owing to its excellent dielectric properties. Combination of the enhanced dipole polarization from the discontinuous PVP aggregations and space charge polarization resulting from the charge transfer between nitroxide radicals (-NO·) leads to high dielectric constant of 14.6 for the blend. The maximum optical direct energy band gap derived from the discontinuous PVP aggregation in the blend also allows for the highest breakdown strength of 365 MV m-1. These results demonstrate that high dielectric constant and high breakdown strength of the blend are attributed to the discontinuous PVP aggregations. It opens a new avenue for exploring all-organic blends with excellent energy storage performance.