Enhanced Capacitive Energy Storage Performance of Polyetherimide Nanocomposites Enabled by 2D Layered Nanostructures and Electrostatic Shielding Mechanisms

The rapid evolution of pulsed-power systems and microelectronic modules, which are demanding ever-higher energy-storage densities, has intensified the search for polymer dielectrics that can deliver both high discharged energy density ( U d ) and robust charge–discharge efficiency ( η ). To address the low energy storage density of polyetherimide (PEI). Two-dimensional montmorillonite nanosheets were synthesized by the liquid-phase intercalation method in this study. Herein, organophilic montmorillonite (OMMT) nanosheets were homogeneously dispersed in polyetherimide (PEI) via solution casting. At only 0.5 wt% OMMT, the resultant film exhibits a relative permittivity of 4.20 while maintaining an ultralow dielectric loss (tan δ < 0.015) across 10 2 –10 5 Hz. Weibull statistics yield a characteristic breakdown strength of 542.98 MV/m, corresponding to a 36.5% increase over neat PEI, and deliver a discharge energy density of 5.68 J cm −3 -an enhancement of 95.9% with charge–discharge efficiency remaining above 80.0%. Finite-element simulations (COMSOL) reveal that the OMMT layers establish an electrostatic shield that impedes electrical-tree propagation, rationalizing the superior breakdown endurance. These results underscore the high-temperature potential of OMMT/PEI nanocomposites for next-generation dielectric capacitors.