High-Temperature Dielectric Energy Storage Materials Fabricated by Crosslinking Titanium Dioxide and Polyarylene Ether Nitrile

Dielectric materials have broad application prospects in the field of high-temperature electronic power systems. Up to now, high-temperature dielectric materials are mainly prepared by using high glass transition temperature (Tg) polymers. However, the incompatibility between polymers and fillers, which are incorporated for high energy density, leads to soaring dielectric losses at high temperatures, resulting in a nosedive of discharged energy density (Ud) and efficiency (η). In this paper, we report the fabrication of high-temperature dielectric materials via the self-crosslinking of phthalonitriles from phthalonitriles modified titanium dioxide (TiO2-2CN) and phthalonitriles terminated polyarylene ether nitrile (PEN-2CN). TiO2-2CN is firstly synthesized and characterized, then incorporated into PEN-2CN to prepare TiO2/PEN nanocomposites, which transform into TiO2-PEN hybrids afterwards. The fabricated TiO2-PEN hybrids are confirmed by the change of SEM sectional morphology, as well as the increase of their Tg and thermal decomposition temperature (Td). With the addition of TiO2-2CN, both the Tg, Td, and Ud of TiO2/PEN nanocomposites are improved. In addition, due to the formation of covalent bonds within TiO2-PEN, the hybrids exhibit excellent high-temperature dielectric energy storage performance. Specifically, at 150 °C, the Ud of 10 wt% TiO2-PEN is 0.60 J/cm−3, which is over 95% of that at RT. Moreover, η is greater than 90% and remains unchanged after 10,000 charge and discharge cycles. This method used for preparing TiO2-PEN hybrids through a self-crosslinking reaction of phthalonitriles provides a new approach for preparing high-temperature dielectric materials.