Charge‐Regulating Two‐Dimensional Interfacial Nanocoatings Enable Ultrahigh Discharge Energy Density in Layered Polymer Nanocomposite Dielectrics

Polymer dielectric films are widely investigated for electrostatic energy storage in power electronics and pulsed‐power technologies because of their high power density and rapid charge–discharge capability. However, under high electric fields, leakage conduction arising from electrode‐induced charge injection and field‐driven carrier transport limits the discharge energy density ( U e ) and charge–discharge efficiency ( η ). Herein, an interface‐engineered layered polymer nanocomposite incorporating spatially differentiated two‐dimensional nanocoatings is designed to regulate charge transport and improve breakdown resistance. Montmorillonite nanosheets (MMT NSs) are selectively assembled at the electrode‐dielectric interfaces, whereas boron nitride nanosheets (BN NSs) are introduced between adjacent dielectric layers. The internal BN NSs interlayers confine carriers and impede through‐thickness transport, while the external MMT NSs coatings promote lateral charge redistribution and reduce persistent electrode‐side charge accumulation. This coordinated interfacial regulation suppresses leakage conduction, local electric‐field intensification, and the development of electrical breakdown pathways. Consequently, the best‐performing multilayer structure among the investigated configurations achieves a discharge energy density of ≈37.3 J cm −3 at 740 MV m −1 . It also maintains a variation in discharge energy density of less than 3% over 60 000 cycles at 200 MV m −1 . This design provides a framework for charge regulation in existing and emerging layered polymer nanocomposite dielectrics.