Synergistically depressed dielectric loss and elevated breakdown strength in core@double-shell structured Cu@CuO@MgO/PVDF nanocomposites

To synergistically bolster breakdown strength (Eb) and restrain dielectric loss in the copper (Cu)/poly(vinylidene fluoride, PVDF) presenting a giant dielectric constant (ε), we explore the PVDF nanocomposites with a serial of core@double-shell Cu@CuO (copper oxide)@MgO (magnesium oxide ) nanofillers with various MgO shell thicknesses. The double-shell CuO@MgO not only improves the interface compatibility between filler and matrix but also increases the energy barrier height for charge migration across the nanocomposites and facilitates the formation of charge traps, thus impeding long-distance carrier transport and resulting in restrained dielectric loss. Further, the MgO shell with appropriate ε and wide bandgap effectively alleviates the strong dielectric mismatch between neat Cu and PVDF, which significantly lessens the local electric field distortion thereby resulting in elevated Eb. Moreover, the overall dielectric performances of the Cu@CuO@MgO/PVDF can be modulated via altering the MgO shell thickness. This core@double-shell strategy offers a new paradigm for the design and preparation of percolating nanocomposites with desirable integrated dielectric performances.