Simultaneously Improved Dielectric Constant and Breakdown Strength of PVDF-based Composites with Polypyrrole Nanowire Encapsuled Molybdenum Disulfide Nanosheets

High-performance dielectric polymer composites have received increasing attention due to their important applications in the field of energy storage. The rational structural design of hybrid fillers can lead to a balance between high dielectric constant and insulation in composites. In this work, novel hybrid fillers were fabricated by in situ synthesizing one-dimensional polypyrrole nanowires (PPynws) on the two-dimensional molybdenum disulfide (MoS2), which integrated the good ion polarization ability of PPynws and the high insulation and adjustable band gap of MoS2. Compared with the binary poly(vinylidene fluoride) (PVDF)/MoS2 composites, the PVDF/MoS2-PPynws composites exhibited remarkably improved dielectric constant and breakdown strength, while the dielectric loss was still maintained at a low level. An optimal ternary composite with 1 wt% MoS2-PPynws showed a high dielectric constant (15@1kHz), suppressed dielectric loss (0.027@1kHz), and high breakdown strength (422.1 MV/m). PPynws inducing strong interfacial polarization and the highly insulated MoS2 nanosheets extending the breakdown path mainly contributed to the synchronously enhanced dielectric constant and breakdown strength. This intriguing synthesis method of PVDF/MoS2-PPynws nanocomposite will open up new opportunities for fabricating nanostructured polymer composites to produce high dielectric materials.