Preparation and Application of PI-Based Amphiphilic Ion Exchange Membranes with High Ion Selectivity
Amphiphilic ion exchange membranes can combine the advantages of proton exchange mem-branes and anion exchange membranes to resolve the trade-off between proton transport capacity and vana-dium ion permeation capacity.In response to many reports,the anion and cation are located in the same side chain which restricts the regulation of their ratios,in the present work,sulfonated polyimide mem-brane materials containing the main chain of the benzimidazole structure were prepared by using 5-amino-2-(4-aminophenyl)benzimidazole,4,4'-diamino-2,2'-disulphonatobiphenyl,and 4,4'-diaminodiphenylsul-fone as the diamine monomers,and 1,4,5,8-naphthalenetetracarboxylic anhydride as the dianhydride monomers.By taking advantage of the easy modifiability of the benzimidazole,amphoteric polyimide membrane materials with the side chain of the long functional group were prepared,which allow the flex-ibility of the ratio of the anion to the cation to the cation to be regulated.QBISPI-x(x=0,33,67,100)series membranes were prepared by modulating the content of long side-chain cationic groups.QBISPI-0,which has the highest proton conductivity(27.462 2 mS·cm-1)and ion selectivity(6.598×105 S·min·cm-3),shows the best performance in the VRFB test,and the energy density can reach 73.6%at high current density(200 mA·cm-2).
amphoteric ion exchange membranepolyimidevanadium redox flow batteryacid-base interactionbenzimidazole
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