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24. Effect of zwitterions on electrochemical properties of oligoether-based electrolytes

Author

Suematsu, Mitsutake, Yoshizawa-Fujita, Masahiro, Zhu, Haijin, Forsyth, Maria, Takeoka, Yuko, Rikukawa, Masahiro, Suematsu, Mitsutake, Yoshizawa-Fujita, Masahiro, Zhu, Haijin, Forsyth, Maria, Takeoka, Yuko, and Rikukawa, Masahiro

Abstract

Solid polymer electrolytes show great potential in electrochemical devices. Poly(ethylene oxide) (PEO) has been studied as a matrix for solid polymer electrolytes because it has relatively high ionic conductivity. In order to investigate the effect of zwitterions on the electrochemical properties of poly(ethylene glycol) dimethyl ether (G5)/lithium bis(fluorosulfonyl) amide (LiFSA) electrolytes, a liquid zwitterion (ImZ2) was added to the G5-based electrolytes. In this study, G5, which is a small oligomer, was used as a model compound for PEO matrices. The thermal properties, ionic conductivity, and electrochemical stability of the electrolytes with ImZ2 were evaluated. The thermal stabilities of all the G5-based electrolytes with ImZ2 were above 150 °C, and the ionic conductivity values were in the range of 0.8–3.0 mS cm−1 at room temperature. When the electrolytes contained less than 5.5 wt% ImZ2, the ionic conductivity values were almost the same as that of the electrolyte without ImZ2. The electrochemical properties were improved with the incorporation of ImZ2. The anodic limit of the electrolyte with 5.5 wt% ImZ2 was 5.3 V vs. Li/Li+, which was over 1 V higher than that of G5/LiFSA.

Published
2015

28. Synthesis and investigation of sulfonated poly( p -phenylene)-based ionomers with precisely controlled ion exchange capacity for use as polymer electrolyte membranes.

Author

Yoshida-Hirahara M, Takahashi S, Yoshizawa-Fujita M, Takeoka Y, and Rikukawa M

Abstract

To achieve precise control of sulfonated polymer structures, a series of poly( p -phenylene)-based ionomers with well-controlled ion exchange capacities (IECs) were synthesised via a three-step technique: (1) preceding sulfonation of the monomer with a protecting group, (2) nickel(0) catalysed coupling polymerisation, and (3) cleavage of the protecting group of the polymers. 2,2-Dimethylpropyl-4-[4-(2,5-dichlorobenzoyl)phenoxy]benzenesulfonate (NS-DPBP) was synthesised as the preceding sulfonated monomer by treatment with chlorosulfuric acid and neopentyl alcohol. NS-DPBP was readily soluble in various organic solvents and stable during the nickel(0) catalysed coupling reaction. Sulfonated poly(4-phenoxybenzoyl-1,4-phenylene) (S-PPBP) homopolymer and seven types of random copolymers (S-PPBP- co -PPBP) with different IECs were obtained by varying the stoichiometry of NS-DPBP. The IECs and weight average molecular weights ( M w s) of ionomers were in the range of 0.41-2.84 meq. g -1 and 143 000-465 000 g mol -1 , respectively. The water uptake, proton conductivities, and water diffusion properties of ionomers exhibited a strong IEC dependence. Upon increasing the IEC of S-PPBP- co -PPBPs from 0.86 to 2.40 meq. g -1 , the conductivities increased from 6.9 × 10 -6 S cm -1 to 1.8 × 10 -1 S cm -1 at 90% RH. S-PPBP and S-PPBP- co -PPBP (4 : 1) with IEC values >2.40 meq. g -1 exhibited fast water diffusion (1.6 × 10 -11 to 8.0 × 10 -10 m 2 s -1 ), and were comparable to commercial perfluorosulfuric acid polymers. When fully hydrated, the maximum power density and the limiting current density of membrane electrode assemblies (MEAs) prepared with S-PPBP- co -PPBP (4 : 1) were 712 mW cm -2 and 1840 mA cm -2 , respectively., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Published
2020
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29. Use of a High-Performance Poly( p -phenylene)-Based Aromatic Hydrocarbon Ionomer with Superacid Groups in Fuel Cells under Low Humidity Conditions.

Author

Oshima T, Yoshizawa-Fujita M, Takeoka Y, and Rikukawa M

Abstract

Aromatic ionomers with perfluoroalkyl sulfonic acid groups for fuel cell applications have been prepared mostly by the post-functionalization method. Herein, we present a direct polymerization method using a novel monomer with a perfluorosulfonic acid group to control the amount and position of the sulfonic acid groups. A poly( p -phenylene)-based aromatic hydrocarbon ionomer bearing a pendant perfluorosulfonic acid group in a substituent at the 2-position is synthesized by Ni(0)-catalyzed coupling polymerization. The direct polymerization provides M n values of up to 169 000 with a highly controlled molecular structure and allows the formation of thin membranes. These ionomers were found to combine the positive features of perfluorinated and aromatic hydrocarbon ionomers, and these thin membranes with a relatively high ion exchange capacity showed high proton conductivity and excellent fuel cell performance (907 mW cm -2 even at 80 °C and 30% RH) under low humidity conditions compared with other reported aromatic hydrocarbon ionomers., Competing Interests: The authors declare no competing financial interest.

Published
2016
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