Significantly enhancing the dielectric constant and breakdown strength of linear dielectric polymers by utilizing ultralow loadings of nanofillers

Dielectric polymers with high electrostatic energy storage capability are the enabling technology for advanced electronics and electric power systems. However, the development of dielectric polymers is rather limited by their undesired discharged energy density (U_e) due to the intrinsic low dielectric constant (K). Although large improvements ofKcan be achieved in dielectric polymers by introducing high filling ratios (>10 vol%) of high-Kinorganic fillers, this approach has had only limited success in enhancing energy density due to the negative impact on the breakdown strength (E_b) and charge-discharge efficiency (η). Herein, we report that the incorporation of ultralow amounts (<1 vol%) of low-Kquantum dot (QD) nanofillers into a linear polymer leads to pronounced and concurrent enhancements in bothKandE_b, yielding a highU_eof 17.6 J cm⁻³with anηof >87% at 800 MV m⁻¹. The improvement ratios ofK(∼69%) andE_b(∼60%) reported in this work represent the record values in linear dielectric polymer composites with low filler content (≤5 vol%). The observed dielectric enhancement is rationalized by the significant contributions of the interface including enhanced polymer chain mobility and induced interfacial dipoles as revealed in the interphase dielectric model and interface simulations based on density functional theory (DFT). The improved mechanical strength and raised interface charge barriers are responsible for the highE_b. This contribution paves a new avenue for designing scalable polymer-based dielectric materials exhibiting high energy densities and efficiencies and provides fundamental insights into the dielectric behaviors at the interfaces in polymer nanocomposites.