Ultrahigh Energy Density Dielectric Capacitor based on 2D MXene-PVDF Heterostructure

Poly(vinylidene fluoride) (PVDF) has been widely used in dielectric capacitors due to its inherently high dielectric constant, low loss tangent, and high breakdown strength. However, a significant improvement in energy density is required owing to the rapid expansion of large-scale energy storage systems and portable electronic devices. Herein, we demonstrate that incorporating two-dimensional (2D) MXene (Ti₃C₂T_x) between thin layers of PVDF film in stacked heterostructure architecture has significantly enhanced the dielectric constant, dielectric strength, and energy density over pristine PVDF. The stacking geometry of PVDF/MXene/PVDF (PMP) capacitor has exhibited 166% improved dielectric constant (ε_av ≈ 40) compared to PVDF (ε_av ≈ 13). Also, it showed excellent discharge energy density of 100 J cm^-3 (E ≈ 467 MV/m) compared to 13 J cm^-3 (E ≈ 395 MV/m) for pristine PVDF capacitor while maintaining the efficiency of the capacitor ~78%. The enhanced interfacial polarization in the PMP heterostructure can be attributed mainly to the large surface area of MXene and the interaction of the polymer with different functional groups of MXene, which promotes efficient charge trapping and accumulation at the MXene-PVDF interface. This study proposes a promising approach to designing polymer-based capacitors using 2D MXene in a heterostructure configuration that holds significant potential for advancements beyond conventional technologies.