Thin-Reinforced Anion-Exchange Membranes with High Ionic Contents for Electrochemical Energy Conversion Processes

Abstract

Ion-exchange membranes (IEMs) are a core component that greatly affects the performance of electrochemical energy conversion processes such as reverse electrodialysis (RED) and all-vanadium redox flow battery (VRFB). The IEMs used in electrochemical energy conversion processes require low mass transfer resistance, high permselectivity, excellent durability, and also need to be inexpensive to manufacture. Therefore, in this study, thin-reinforced anion-exchange membranes with excellent physical and chemical stabilities were developed by filling a polyethylene porous substrate with functional monomers, and through in situ polymerization and post-treatments. In particular, the thin-reinforced membranes were made to have a high ion-exchange capacity and a limited degree of swelling at the same time through a double cross-linking reaction. The prepared membranes were shown to possess both strong tensile strength (>120 MPa) and low electrical resistance (<1 Ohm cm2). As a result of applying them to RED and VRFB, the performances were shown to be superior to those of the commercial membrane (AMX, Astom Corp., Japan) in the optimal composition. In addition, the prepared membranes were found to have high oxidation stability, enough for practical applications.

Tuning the Hydrophobic Component in Reinforced Poly(arylimidazolium)-Based Anion Exchange Membranes for Alkaline Fuel Cells

“…First, 4,5-bis(4-chlorophenyl)-2mesityl-1H-imidazole (MIm) and the alkylated 4,5-bis(4chlorophenyl)-1-ethyl-2-mesityl-1H-imidazole (MEIm) monomers were prepared via the modified procedure from the literature. 36 The 1 H and 13 C NMR spectra of MIm and MEIm were consistent with the supposed structures (Figures S1 and S2). Mass spectrum and HPLC analysis revealed that MEIm had identical formula weight (M w = 435, [M + H] + ) and >99.9% purity (Figures S3 and S4).…”

“…Second, AEMs should possess dimensional stability since fuel cells produce water as a byproduct which results in membrane swelling. Such swelling often causes mechanical failure and performance loss in operating fuel cells. , Introducing clusters of the ammonium groups, cross-linking (thermal or chemical), , or reinforcement with hydrophobic porous substrates , were reported as effective strategies to address the trade-off relationship between the ion conductivity and swelling; improving ion conductivity by increasing the ion exchange capacity (IEC) mostly results in increased water absorbability and membrane swelling. − Third, AEMs (ammonium cations and polymer main chains) have to withstand nucleophilic attack by hydroxide ions. Particularly, low hydration levels (at low humidity) are known to aggravate the alkaline degradation .…”