Designing tailored combinations of structural units in polymer dielectrics for high-temperature capacitive energy storage

Abstract

Many mainstream dielectric energy storage technologies in the emergent applications, such as renewable energy, electrified transportations and advanced propulsion systems, are usually required to operate under harsh-temperature conditions. However, excellent capacitive performance and thermal stability tend to be mutually exclusive in the current polymer dielectric materials and applications. Here, we report a strategy to tailor structural units for the design of high-temperature polymer dielectrics. A library of polyimide-derived polymers from diverse combinations of structural units are predicted, and 12 representative polymers are synthesized for direct experimental investigation. This study provides important insights into decisive structural factors necessary to achieve robust and stable dielectrics with high energy storage capabilities at elevated temperature. We also find that the high-temperature insulation performance would experience diminishing marginal utility as the bandgap increases beyond a critical point, which is strongly correlated to the dihedral angle between neighboring planes of conjugation in these polymers. By experimentally testing the optimized and predicted structures, an increased energy storage at temperatures up to 250 °C is observed. We discuss the possibility for this strategy to be generally applied to other polymer dielectrics to achieve further performance enhancement.

Increasing Twist Rigidity to Prepare Polyimides with Low Dielectric Constants and Dissipation Factors over a Wide Temperature Range

“…From the simulation results, it is this change in the rotational energy barrier of the imide C–N bond that leads to a more rigid distortion of the 6FDA-GB backbone. Here, the molecular structure with higher rotational energy barrier is more difficult to approach the coplanar state, resulting in a weakly interacting stable state, and a higher free volume fraction . On the other hand, the impeded rotation of the C–N bonds of the imine ring due to the increased rigidity of the distortion would also lead to a weakening of the deflection motion of the dipole.…”

Biaxially oriented films of grafted-polypropylene with giant energy density and high efficiency at 125 °C

“…2 Recently, with the rapid growth of high-power energy storage and pulse power systems such as renewable offshore wind energy, power grid frequency modulation, electric vehicles, advanced electromagnetic weapons, downhole oil, and outer space explorations, 3,4 more stringent temperature capabilities are demanded to overcome the challenges. 5–8 For example, in hybrid electric vehicles (HEVs), the near-engine-temperature may exceed 120 °C. However, the state-of-the-art BOPP capacitors can merely operate at 85 °C with the charge–discharge efficiency maintained at 95% near the breakdown strength.…”

Enhancing high‐temperature breakdown strength of polyetherimide dielectric nanocomposites with MgO nanosheets by inhibiting charge migration

“…Recently, the demand for polymer‐based dielectrics used in high‐temperature conditions (>140°C) has increased with the rapid evolution of numerous industrial applications such as hybrid vehicles, oil drilling, and electrified aircraft 9–11 . The biaxially oriented polypropylene (BOPP) polymer, currently leading commercial dielectric material, possesses an energy density of ~2 J cm −3 and has shown its capability to work at temperatures below 105°C 12–14 . It restricts its usage in high‐temperature applications.…”