Multi-Interface Polarization Modulation in Cu@TiO2@MgO/PVDF for Enhanced Dielectric Constant and Breakdown Performances.

Decoupling control and collaborative improvement in both dielectric constant (ε) and breakdown strength (Eb) while holding low loss of polymeric composites, constitutes a challenge for power electronics and energy storage systems. To realize this objective in copper (Cu)/polyvinylidene fluoride (PVDF) nanocomposites, the Cu nanoparticles were initially coated with titanium oxide (TiO2) and magnesium oxide (MgO), respectively, followed by compounding with PVDF to investigate the double‑shell' effect on dielectric performance. The results demonstrate that the Cu@TiO2@MgO/PVDF displays elevated ε and Eb, along with lower loss dissipation (tanδ) when compared to Cu/PVDF. The increased ε is attributed to the enhancement of both high-frequency intra‑particle and low‑frequency inter‑particle polarizations resulting from the double-interlayer. The TiO2@MgO not only prevents direct contact between Cu nanoparticles but also creates charge traps, reducing the tanδ and leakage conductivity. The double shell mitigates interfacial dielectric parameter mismatch, thereby enhancing the Eb. Simulations and theoretical calculations reveal the multiple polarization mechanisms and the regulated charge transport behavior in the Cu@TiO2@MgO/PVDF. The conductive core-insulating double-shell strategy provides an insightful view on promoting multiple polarizations and suppressing charge migration in percolating polymer nanocomposites. The Cu@TiO2@MgO/PVDF with boosted ε and Eb alongside suppressed tanδ showcases appealing potential applications in power electronic devices.