Characterization of semi-interpenetrating polymer electrolytes containing poly(vinylidene fluoride-co-hexafluoropropylene) and ether-modified polysiloxane

This work presents a detailed study of a semi-interpenetrating polymer network (semi-IPN) consisting of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), polysiloxane-comb-propyl(triethylene oxide) (PSx) and lithium bis(trifluoromethane)sulfonimide (LiTFSI) prepared by a solution casting technique. According to differential scanning calorimetry (DSC), formation of the PVDF-HFPs crystalline phase is inhibited by the PSx which results in a significant improvement of tensile strain. A homogeneous distribution of PVDF-HFP and PSx in the membrane is analyzed using micro-FTIR mapping. Since no peak-shift due to mixing of PVDF-HFP and PSx was observed in FTIR second derivative analysis, computational models were applied to investigate the intermolecular interactions between the constituting domains of different polarity. An influence of PVDF-HFP on the Li+ transport in the ion-conducting PSx was determined by calculating the effective conductivities. The highest ionic conductivity of 7.7 × 10- 5 S cm- 1 at room temperature was reached with 15 wt.% LiTFSI. The electrochemical stability window ranges from 0.5 V to 4.6 V vs. Li/Li+ reference electrode

Highly-fluorous pyrazolide-based lithium salt in PVDF-HFP as solid polymer electrolyte

For the first time, the concept of fluorophilicity f(i) is adapted to the development of a novel solid polymer electrolyte (SPE) by computationally evaluating a new class of lithium salts, the perfluoroalkylated pyrazolides. An SPE consisting solely of poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) and different concentrations of highly-fluorous lithium [5-(perfluorobutyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl] trifluoroborate (LiPFAPB14) is reported. Membranes with a salt concentration up to 80 wt.% are prepared and are investigated by 3D laser scanning confocal microscopy, scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) concerning the correlation between the LiPFAPB14 salt concentrations with the miscibility in PVDF-HFP. Membrane performances as SPE are evaluated by impedance spectroscopy revealing ionic conductivities of 1.4 x 10(-4) S cm(-1) at 90 degrees C with 80 wt.% LiPFAPB14

3D laser scanning confocal microscopy of siloxane-based comb and double-comb polymers in PVDF-HFP thin films

Currently, atomic force microscopy is the preferred technique to determine roughness on membrane surfaces. In this paper, a new method to measure surface roughness is presented using a 3D laser scanning confocal microscope for high-resolution topographic analysis and is compared to conventional SEM. For this study, the surfaces of eight samples based on a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) host polymer with different liquid interpenetrating components were analyzed. Polymethylhydrosiloxane, triethylene glycolallylmethyether, (3,3,3-trifluoropropyl) methylcyclotrisiloxane (D-3-C2H4CF3), polysiloxane-comb-propyloxymethoxytriglycol (PSx), poly-siloxane-comb-propyl-3,3,3-trifluoro (PSx-C2H4CF3), poly [bis(2-(2-methoxyethoxy) ethoxy) phosphazene, or poly [bis(trifluoro) ethoxy] phosphazene was chosen as interpenetrating compound to investigate the impact of comb and double-comb-structured polymer backbones, as well as their dipolar or fluorous residues on the PVDF-HFP-miscibility. Different phases of the constituting ingredients were identified via their thermal properties determined by DSC. Additionally, the COSMO-RS method supported the experimental results, and with regard to computed sigma-profiles, new modified structures for polysiloxane and polyphosphazene synthesis were suggested