Record Efficiency of β-Phase PVDF-MXene Composites in Thin-Film Dielectric Capacitors

Polyvinylidene fluoride (PVDF) is a semicrystalline polymer used in thin-film dielectric capacitors because of its inherently high dielectric constant and low loss tangent. Its dielectric constant can be increased by the formation and alignment of its β-phase crystalline structure, which can be facilitated by 2D nanofillers. 2D carbides and nitrides, MXenes, are promising candidates due to their notable dielectric permittivity and ability to increase interfacial polarization. Still, their mixing is challenging due to weak interfacial interactions and poor dispersibility of MXenes in PVDF. This work explores a novel method for delaminating Ti₃C₂T_x MXene directly into organic solvents while maintaining flake size and quality, as well as the use of a non-solvent-induced phase separation method for producing both dense and porous PVDF-MXene composite films. A deeper understanding of dielectric behavior in these composites is reached by examining MXenes with both mixed and pure chlorine terminations in PVDF matrices. Thin-film capacitors fabricated from these composites display ultrahigh discharge energy density, exceeding 45 J cm^-3 with 95% efficiency. The PVDF-MXene composites are also processed using a green and sustainable solvent, propylene carbonate.