Polyetherimide composite dielectrics enhance energy storage performance by oriented one-dimensional BZCT@BT@S core–shell fillers

The advancement of dielectric capacitors toward achieving high-energy storage density requires polymer-based dielectric materials with both high breakdown strength ( E b ) and high dielectric constant ( ε r ). However, the inherent trade-off between E b and ε r limits further enhancement of energy storage density. In this study, a design approach involving inorganic fillers with gradient dielectric matching is proposed for a double core–shell structure. Barium calcium zirconate titanate (BZCT) nanofibers are utilized as fillers within a double core–shell structure (BT + SiO 2 ), embedded into a polyetherimide (PEI) matrix through electrostatic spinning with an oriented arrangement. This results in the fabrication of BZCT nanofibers PEI-based composite dielectrics with parallel double core–shell structure, demonstrating exceptional energy storage performance. Specifically, the composite dielectric (0.5%-10% BZCT@BT@S/PEI) achieves a charge/discharge efficiency ( η ) of 93.29% and a discharge energy density ( U e ) of 6.97 J/cm 3 with BT and BZCT contents of 0.5% and 10%, respectively. The results show that BZCT enhances the ε r of the composite dielectric, while the double core–shell structure of BT + SiO₂ leads to a gradient change in ε r . This strategy not only can reduce the electric field( E ) distortion caused by the dielectric mismatch between the PEI matrix and BZCT, but also the double core–shell structure shows a relatively significant synergistic effect, successfully increasing the E b of the composite dielectric, with simulation results supporting the design rationale behind the double core–shell structure. This investigation introduces an insight for designing energy storage composite dielectrics. Graphical abstract The alternative text for this image may have been generated using AI.