Fang Wang,Xianhong Zhang,Yuhong Ma,Dong Chen,Wantai Yang
A novel flexible dielectric composite with halloysite nanotube-poly(3,4-ethylenedioxythiophene) (HNTs-PEDOT) hybrid as conductive filler and poly(vinylidene fluoride) (PVDF) as polymer matrix were prepared via a blending and hot-pressing technique. HNTs-PEDOT hybrid, with PEDOT coated onto both the negatively charged inner and out surfaces of the HNTs tubes, were fabricated by chemical oxidative polymerization of EDOT with unmodified HNTs as templates. The conductivity of HNTs-PEDOT hybrid with 50 wt% HNTs is up to 12.89 S/cm, which is 100 times greater than that of pure PEDOT (about 0.12 S/cm) synthesized under the similar condition. With PEODT as outside organic layer, HNTs-PEDOT could be easily dispersed in PVDF matrix uniformly. In addition, with the introduction of HNTs-PEDOT into PVDF matrix, it makes a phase transformation of PVDF from α to electroactive β phase. HNTs-PEDOT/PVDF shows good dielectric performance. At close to the percolation threshold value ( f HNTs-PEDOT = 0.11), the dielectric constant of HNTs-PEDOT/PVDF is up to 641 at 1000 Hz, which is attractive to prepare flexible materials.
Xiangcong He,Wenna Liu,Hui Fu,Chris R. Bowen,Jizhong Liu,Xie Li,Abdul Rehman Akbar,Jinju Zheng,Weiyou Yang
Incorporating perovskite nanocrystals (PNCs) into poly(vinylidene fluoride) (PVDF) is an effective method to improve the performance of PVDF-based piezoelectric nanogenerators (PENGs). The conventional techniques are typically performed via a two-step process, namely, the synthesis of PNCs and then introducing them into the PVDF matrix. Here, we report the exploration of flexible PENG with boosted performance by in situ growth of Zr-doped Cs2Ag0.3Na0.7InCl6 double perovskites (ZCDP) within the PVDF matrix (PENGin). The as-constructed PENGin delivers an open-circuit voltage of 44.4 V and a short-circuit current density of 10 μA cm–2, both of which are more than 2 times those of PENGs built by a conventional two-step process and ∼6 and ∼9 times the best ones of in situ grown Cs2InI6@PVDF-based PENGs ever reported, respectively. The enhanced performance could be ascribed to the optimized spontaneous polarization, thanks to the uniform dispersion of PNCs with a solid ZCDP/PVDF interface within the matrix, which collectively facilitates the electron migration and aggregation, thereby establishing a strong built-in electric field to amplify the dipole spontaneous polarizability. Additionally, the PENGin exhibits excellent performance with robust stability in pressure sensing, wearable energy harvesting, and DC power applications, representing its promise toward practical use.
Porous membranes fabricated from poly(vinylidene fluoride) (PVDF) and a star polymer with linear poly(ethylene glycol) (PEG) arms and cycloPEG cores were fabricated via the phase-separation method. The porous gel polymer electrolytes (PGPEs) were obtained by immersing the porous membranes in the electrolyte solution. When the additive amount of star polymer was up to 20 wt %, the prepared membrane had the largest porosity and the pores were uniformly distributed in the membrane. The star polymer can not only decrease the crystallization of PVDF and enhance the absorption of liquid electrolyte but also offer ion conduction channels (cycloPEG cores). Therefore, the PGPE with 20 wt % star polymers exhibited competitive ionic conductivities of 1.27 mS cm–1 at 30 °C and 2.89 mS cm–1 at 80 °C. To stabilize the liquid electrolyte in the holes of porous membranes, a gelator was introduced in the liquid electrolyte to form gelled porous gel polymer electrolytes (GPGPEs), and the leakage of liquid electrolytes was thus remarkably reduced. The ionic conductivity of GPGPEs with 20 wt % star polymer and 1.5 wt % gelator was importantly improved at high temperatures (6.02 mS cm–1 at 80 °C). We systematically investigated the electrochemical performances of PGPEs without star polymer, PGPEs with star polymer, and GPGPEs with star polymer. The incorporation of star polymers with linear PEG arms and cycloPEG cores into the PGPEs and GPGPEs significantly improved the electrochemical performances of the lithium metal/LiFePO4 cell assembled with the PGPEs or GPGPEs.
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