Engineering Poly(phthalazinone ether sulfone) Dielectric Films for Stable High-Temperature Capacitive Energy Storage

Poly(aryl ether) (PAE) dielectrics have captured widespread interest in the domain of film capacitors primarily due to their exceptional high-temperature endurance, advantageous film-forming capabilities, and superior mechanical attributes. However, the conventional PAEs had a complicated film-forming process and low discharge energy density. In order to solve this problem, a poly(phthalazinone ether sulfone) (PPES) with phthalazinone structures is synthesized. Compared to the commercial polysulfone, the PPES exhibits significantly higher discharge energy density (Ue) and breakdown strength both at room temperature and elevated temperature. In particular, the Ue value of PPES (3.66 J/cm3) at 150 °C and 500 MV/m is even superior to that of commercially available bi-oriented polypropylene dielectric films, which are only 2.71 J/cm3 at room temperature and 450 MV/m. This investigation has demonstrated that the PPES films with phthalazinone structures are highly promising for energy storage under harsh conditions.