2D nanoarchitecture-engineered polyetherimide dielectrics with thermally stable permittivity-breakdown dual enhancement

Abstract

To address the increasing demand for capacitive energy storage in high-temperature environments, the development of polymer dielectrics with high energy storage density, energy efficiency, and excellent thermal stability is critical. Here, ultra-low loadings (<0.5 wt%) of wide-bandgap (∼3.43 eV) two-dimensional CaBi₂Nb₂O₉ (CBN) flakes are incorporated into a polyetherimide (PEI) polymer matrix. The addition of CBN flakes increases Young's modulus and bandgap of the nanocomposite, which helps to block the propagation of electrical trees, as indicated by the simulation results. This also suppresses carrier migration and effectively reduces high-temperature leakage current density, leading to a significant improvement in the breakdown strength and energy density of the CBN/PEI nanocomposites at high temperatures. For instance, the PEI nanocomposites with 0.3 wt% achieve an energy density of 3.24 J/cm³ with an efficiency (η) exceeding 90 % at 150 °C. Even at 200 °C, with η > 90 %, the discharge energy density remains as high as 2.22 J/cm³, which is 90 % higher than that of PEI. Notably, after 10⁵ charge-discharge cycles, no degradation in energy density or efficiency is observed at elevated temperatures. This study presents a straightforward and broadly applicable strategy for developing high-temperature polymer dielectrics.