Effect of sol–gel-derived core–shell MXene@TiO2 fillers on the dielectric properties of PVDF-based composites

TiO 2 was deposited on the surface of Ti 3 C 2 T x MXene by the sol–gel method to construct core–shell structured MXene@TiO 2 fillers, which were then introduced into the PVDF matrix to prepare dielectric composite films. The effects of TiO 2 deposition ratio and filler loading on the dielectric properties of the composites were systematically investigated, and the thermal and mechanical properties of the optimized system were further evaluated. The results showed that the TiO 2 coating layer could construct an effective interfacial insulating structure, which enhanced interfacial polarization while suppressing carrier migration and the formation of leakage pathways, thereby enabling the synergistic regulation of dielectric constant and dielectric loss. When the TiO 2 deposition mass ratio reached 50%, the composites showed a more effective overall interfacial modulation effect. Under these conditions, the 15 wt% composite delivered the optimal overall dielectric performance, with a dielectric constant of 29.1 and a dielectric loss as low as 0.051, representing a significant reduction compared with that of the unmodified MXene/PVDF composite (0.59), and it also exhibited superior dielectric stability. At the same time, the thermal stability and mechanical performance of the composites were also enhanced. The study confirms that building a TiO 2 interfacial insulating layer is an effective approach to enhancing the dielectric performance of PVDF-based composites while realizing the coordinated optimization of multiple properties.