Ultrahigh Contentβ-Phase and SuperiorPiezoelectric Output Performance of Poly(vinylidene fluoride)-BasedFlexible Composite Films Containing Low-Loaded MoS 2 /SnO 2 Heterostructured Nanofillers

Achieving a high β-phase content in poly(vinylidene fluoride) (PVDF) using low filler loadings remains a key challenge for flexible piezoelectric composites. Herein, a heterostructured MoS2/SnO2 nanofiller was designed to efficiently induce the nonpolar α-to-polar β-phase transition via interfacial charge transfer and built-in electric field effects. SnO2 nanoparticles were grown in situ onto the exfoliated MoS2 nanosheets to construct a 0D/2D heterojunction. At the interface, the work function difference drove charge transfer and interfacial polarization, which generated a strong built-in electric field, which synergistically promoted the alignment of PVDF’s-CF2-dipoles, in the presence of increased surface area and enhanced local stress transfer, thereby efficiently inducing the β-phase crystallization. PVDF/MoS2–SnO2 composite films containing 1.0 wt % heterostructured nanofiller were prepared by solution casting, and an optimal composite of PVDF/MoS2@SnO2 exhibited an ultrahigh β-phase content of 80.2% (in comparison to a typical 10% for neat PVDF) as well as a fracture elongation above 15% (demonstrating its good flexibility). Under periodic pressure, it showed significantly enhanced electrical output: an open-circuit voltage of 5.92 V and a short-circuit current of 365.70 nA, which were averagely three times those of neat PVDF. The present work confirmed the efficacy of the MoS2/SnO2 heterostructure, which could provide a filler design strategy for high-performance, flexible piezoelectric composite films, highlighting their potential in sensing and energy harvesting.