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Diels alder polyphenylene anion exchange membrane for nonaqueous redox flow batteries

Journal of the Electrochemical Society

Small, Leo J.; Pratt, Harry P.; Fujimoto, Cy F.; Anderson, Travis M.

Here highly conductive, solvent-resistant anionic Diels Alder polyphenylene (DAPP) membranes were synthesized with three different ionic contents and tested in an ionic liquid-based nonaqueous redox flow battery (RFB). These membranes display 3-10× increase in conductivity in propylene carbonate compared to some commercially available (aqueous) anion exchange membranes. The membrane with an ion content of 1.5 meq/g (DAPP1.5) proved too brittle for operation in a RFB, while the membrane with an ion content of 2.5 meq/g (DAPP2.5) allowed excessive movement of solvent and poor electrochemical yields (capacity fade). Despite having lower voltage efficiencies compared to DAPP2.5, the membrane with an intermediate ion content of 2.0 meq/g (DAPP2.0) exhibited higher coulombic efficiencies (96.4% vs. 89.1%) and electrochemical yields (21.6% vs. 10.9%) after 50 cycles. Crossover of the electroactive species was the primary reason for decreased electrochemical yields. Analysis of the anolyte and catholyte revealed degradation of the electroactive species and formation of a film at the membrane-solution interface. Increases in membrane resistance were attributed to mechanical and thermal aging of the membrane; no chemical change was observed. Improvements in the ionic selectivity and ionic conductivity of the membrane will increase the electrochemical yield and voltage efficiency of future nonaqueous redox flow batteries.

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TYPE Journal Article YEAR 2016
ScopusOSTIDOI

Poly(phenylene)-based anion exchange membranes for alkaline fuel cells

ECS Transactions

Hibbs, M.R.; Fujimoto, Cy F.; Cornelius, C.J.

Cationic polymer membranes that conduct free anions comprise an enabling research area for alkaline membrane fuel cells and other solid-state electrochemical devices that operate at high pH. The synthesis of anion exchange membranes based on a poly(phenylene) backbone prepared by a Diels-Alder reaction is demonstrated as a potential material for alkaline fuel cells. The poly(phenylene)s have benzylic methyl groups that are converted to bromomethyl groups by a radical reaction. Cationic polymers result from conversion of the bromomethyl groups to ionic moieties by quaternization with trimethylamine in the solid state. The conversion to benzyltrimethyl ammonium groups is incomplete as evidenced by the differences between the IEC values measured by titration and the theoretical IECs based on 1H NMR measurements. The anion exchange membranes formed from these polymers have hydroxide ion conductivities as high as 50 mS/cm in liquid water and they are stable under highly basic conditions at elevated temperatures. ©The Electrochemical Society.

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TYPE Conference YEAR 2009
ScopusOSTI
Results 26–50 of 57
Results 26–50 of 57