Breakdown Field Strength Enhancement in Polystyrene Dielectrics from Ultra‐Dilute ZnSe and NiO Particles

ABSTRACT There is an ongoing need to increase the electric field breakdown strength of polymer capacitors to realize increased energy storage density. The incorporation of charge‐trapping nanoparticles is a constructive strategy, but is limited because of agglomeration of particles, increased dielectric loss, brittleness, and difficult scalability. Here we report the development of micron‐thick polystyrene (PS) composite capacitors (NiO:PS and ZnSe:PS) featuring dilute NiO and ZnSe nanoparticles embedded in a PS matrix. The addition of nanofillers significantly enhanced the breakdown strength of the dielectric composites compared to pristine PS, with several such compositions showing breakdown strengths on the order of 6 MV/cm. From a wide range of nanoparticle concentrations for each composite, the best‐performing samples had ultra‐low concentration levels (25 ppmw). Furthermore, the bilayer dielectric architecture was explored, and the results were consistent with trends observed in single‐layer capacitors, accompanied by additional performance improvements. Bilayer structures demonstrated better cycling stability than their single‐layer counterparts, and in some cases also had narrower breakdown field ranges. Our findings underscore the critical role of dilute nanofillers in boosting the dielectric performance of polymer‐based capacitors. Lastly, we discuss the underlying charge transfer and trapping mechanisms contributing to these enhancements.