TiO2 Nanoparticle/Polyimide Nanocomposite for Ultrahigh-Temperature Energy Storage.

With the development of electronic technology, there is an increasing demand for high-temperature dielectric energy storage devices based on polyimides for a wide range of applications. However, the current nanofillers/PI nanocomposites are used for energy harvesting at no more than 200 °C, which does not satisfy the applications in the oil and gas, aerospace, and power transmission industries that require an operating temperature of 250-300 °C. Therefore, we introduced a nanocomposite based on nonsolid TiO2 nanoparticles and polyimide (PI) with high energy storage performance at an ultrahigh temperature of 300 °C. The synergy of excellent dielectric properties and a high breakdown strength endowed the nanocomposite with a low loading content of 1 wt% and a high energy storage density of 5.09 J cm-3. Furthermore, we found that the nanocomposite could stably operate at 300 °C with an outstanding energy storage capability (2.20 J cm-3). Additionally, finite element simulations demonstrated that the partially hollow nanostructures of the nanofillers avoided the evolution of breakdown paths, which optimized the breakdown strength and energy storage performance of the related nanocomposites. This paper provides an avenue to broaden the application areas of PI-based nanocomposites as ultrahigh-temperature energy-storage devices.

Automated real-time study of the defect-induced breakdown occurring on a film-electrode system under a high electric field.

The energy storage density of a capacitor depends on its relative permittivity and breakdown strength. Breakdown of a thin film always first occurs at weak defect spots of dielectrics under a high electric field. It is of great significance to study the defect-induced breakdown of dielectrics to improve the breakdown strength of the dielectric. The majority of studies about the defect-induced breakdown only determine a certain voltage inducing the breakdown, and the single-hole breakdown spots influence the defect-induced breakdown and the intrinsic breakdown under a high electric field, which is hard to facilitate the in-depth study of improving the breakdown strength. Herein, the self-healing breakdown techniques are applied to avoid the influence of single-hole breakdown. An automated real-time testing system is used to study the defect-induced breakdown of various complex film-electrode systems, which accomplishes the temporal and spatial localization of breakdown events according to the physical chemistry characteristics of breakdowns and intelligently displays breakdown events, and detailed classification methods of the defect-induced breakdown are discussed concisely and efficiently. This real-time testing system is effective in revealing the defect-induced breakdown of various complex film-electrode systems under a high electric field, paving the way for uncovering the breakdown mechanism and studying how to improve the capacitor's breakdown strength and energy density.