PEI-Based Nanocomposite with Dual-Functionally Complementary Fillers for Synergistic Enhancement of Energy Storage Performance

Abstract

Dielectric materials with high energy storage performance are in urgent demand for the miniaturized energy storage and integration of modern power electronic devices. However, traditional polymer dielectric materials generally face the bottleneck that energy storage density (Ue) and energy storage efficiency (η) are difficult to improve synchronously, which limits their wide application, especially in extreme environments. Polyetherimide (PEI), featuring high-temperature stability and low dielectric loss, is a research hotspot in the field of energy storage currently. Nevertheless, its relatively low dielectric constant (εr) often fails to yield satisfactory Ue. Herein, using PEI as the matrix, we introduced two functionally complementary fillers, zeolitic imidazolate framework-67 (ZIF-67) and barium titanate nanoparticles (BaTiO3 NPs), and fabricated sandwich-structured BaTiO3/ZIF-67/PEI dielectric composites via a solution casting method. The composite is characterized by a middle layer with mixed distribution of BaTiO3 NPs and ZIF-67, while the outer layers are pure PEI. In this design, BaTiO3 NPs effectively enhance the polarization intensity of the composite through their high εr and the interfacial polarization among BaTiO3 NPs, ZIF-67, and PEI. Meanwhile, ZIF-67 and the PEI matrix form charge traps, which suppress charge migration and dielectric loss (tanδ). The results indicate that at room temperature, with filler contents of 0.5 wt% ZIF-67 and 24.64 wt% BaTiO3 NPs, the nanocomposite achieves a high Ue of 16.23 J/cm3 and maintains an η of 94.33% under an electric field of 527.5 MV/m, exhibiting overall performance superior to most reported polymer-based dielectric composites. Furthermore, it maintains excellent energy storage performance at 130 °C, achieving a Ue of 7.85 J/cm3 at 482.5 MV/m. The synergistic enhancement mechanism of this dual-filler system offers a new strategy for developing highperformance polymer-based dielectric composites by resolving the trade-off between Ue and η.