Improved high-temperature energy storage properties of PEI-based films via constructing an electric potential well

Abstract

The high-temperature energy storage performance of polyetherimide (PEI) remains a challenge due to severe conduction losses and compromised breakdown strength. In this work, montmorillonite–chitosan (CMC) was incorporated into PEI films via the solution casting method to improve the high-temperature energy storage properties of PEI-based films. The effect of the CMC content on microstructure and energy storage properties of the films was studied in detail. The finite element simulation reveals that an electric potential well was formed due to the introduction of CMC, which impedes charge acceleration and deflects electrical tree propagation. Leakage current and thermally stimulated depolarization current analyses further corroborate that the addition of CMC enhances the deep electron trap effect in the films, thereby effectively improving high-temperature energy storage properties. The optimized PEI-based films with 0.025 wt% CMC exhibit an excellent discharge energy density of 5.23 J cm⁻³ with 82% efficiency at 100 °C. At 150 °C, the films still maintain an ultrahigh breakdown strength of 600 MV m⁻¹ and discharge energy density of 4.0 J cm⁻³. The study supplies a strategy to improve high-temperature energy storage properties of PEI-based films.