Sandwich-Architected MXene@TiOx/PVA Composite Films With Augmented Dielectric Performance and Energy Storage Capability

Flexible dielectric materials with elevated dielectric constants and enhanced electrical breakdown resistance are critical for energy storage and wearable electronics. Herein, we developed a dual-strategy approach to enhance the dielectric performance of polyvinyl alcohol (PVA) based composites: (1) surface modification of Ti 3 C 2 T x MXene via H 2 O 2 oxidation to construct insulating TiO x coatings, and (2) structural engineering via a three-layer sandwich design. The MXene@TiO x /PVA interlayer was confined between pure PVA barrier layers using sequential solution casting. Systematic characterization confirmed the formation of amorphous TiO x coatings that effectively mitigates dielectric dissipation while improving voltage endurance. Furthermore, the sandwiched structure construction further improved these properties, leading to superior dielectric properties. The optimized composite with 2 wt.% Ti 3 C 2 T x MXene@TiO x in the interlayer demonstrated a dielectric constant of 12.62 (at 100 Hz) with ultralow loss tangent of 0.059, while achieving a breakdown strength of 194.2 kV/mm and an energy density of 2.25 J/cm 3 . This synergistic strategy of surface passivation and structural engineering provides a scalable pathway for designing eco-friendly dielectric composites with balanced electrical performance.