Morphology and Electrochemical Properties of a Gel Blend Polymer Electrolyte Based on PVDF-HFP/PEO Blend

Document Type : Research Paper

Authors

1 1Mahshahr Campus, Amirkabir University of Technology, Department of Polymer Engineering, P.O. Box 63517-13178, Mahshahr, Iran

2 3Department of Polymer Engineering and Color Technology, Amirkabir University of Technology, P.O. Box 15875-4413, Tehran, Iran

3 Department of Plastics, Faculty of Processing, Iran Polymer and Petrochemical Institute, P.O. Box 14975-112, Tehran, Iran

4 5Department of Applied Chemistry, Faculty of Science, South Tehran Branch, Islamic Azad University, P.O. Box 177761-13651, Tehran, Iran

5 Department of Research and Development, Avrand Pishro Company, P.O. Box 196694-4714Tehran, Iran

6 Department of Chemistry, Materials and Chemical Engineering “Giulio Natta,”, Politecnico di Milano, Milano, Italy

Abstract

Hypothesis: In recent years, gel polymer electrolytes (quasi-solid state electrolytes) have attracted great attention as a suitable substitute for liquid electrolytes. On the other hand, ionic liquids could dramatically enhance the ionic conductivity of electrolytes. In this work, gel polymer electrolytes based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)/poly(ethylene oxide) (PEO) blends (for application in dye-sensitized solar cells (DSSCs)) and imidazolium-based ionic liquids were prepared. It is supposed that blending these two polymers could reduce the degree of crystallization and increase the porosity of the electrolyte blend to yield a higher electrolyte uptake and ionic conductivity.   
Methods: Polymer blend electrolytes were prepared in different blend ratios and in the presence of either one of the ionic liquids including BMII or BMIMBF4 through phase inversion method and their properties were investigated by differential scanning calorimetry (DSC), mercury porosimetry, electrolyte uptake, and morphology to optimize the blend ratio.  
Findings: It was found that the blend ratio of 60/40 (w/w) PVDF-HFP/PEO has the highest porosity and electrolyte uptake. Crystallization investigations by DSC showed that there is a direct relationship between the decrease of crystallinity of two polymers and the increment of electrolyte ionic conductivity. Electrolyte uptake gradually increased with increasing PEO component concentration up to 40 wt%, and reached a maximum of 98.49% and 89.48% for BMIMBF4 and BMII, respectively. Beyond this concentration, a decrease in electrolyte uptake was seen, which is an undesirable feature for the produced samples. In this blend ratio ionic conductivity was measured as 2.07 mS/cm and 1.78 mS/cm for PVDF-HFP/PEO/BMIMBF4 and PVDF-HFP/PEO/BMII electrolytes, respectively.

Keywords


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