Ion conductivemembranes (ICMs) are frequently used as separators for energy conversion and storage technologies of fuel cells

flowbattery

and hydrogen pump

because of their good ion-selective conduction and lowelectronic conductivity. Firstly

this feature article reviews the recent studies on the development of new nonfluorinated ICMs with low cost and their macro/micro-structure control. In general

these new non-fluorinated ICMs have lower conductivity than commercial per-fluorinated ones

due to their poor ion transport channels. Increasing ion exchange capacity (IEC) would create more continuous hydrophilic channels

thus enhancing the conductivity. However

high IEC also expands the overall hydrophilic domains

weakens the interaction between polymer chains

enhances the mobility of polymer chains

and eventually induces larger swelling. The micro-scale expansion and macro-scale swelling of the ICMs with high IEC could be controlled by limiting the mobility of polymer chains. Based on this strategy

some efficient techniques have been developed

including covalent crosslinking

semi-interpenatrating polymer network

and blending. Secondly

this review introduces the optimization of macro/microstructure of both per-fluorinated and non-fluorinated ICMs to improve the performance. Macro-scalemultilayer composite is an efficientway to enhance the mechanical strength and the dimensional stability of the ICMs

and could also decrease the content of perfluorosulfonic acid resin in the membrane

thereby reducing the cost of the per-fluorinated ICMs. Long side chain

multiple functionalization

smallmolecule inducing micro-phase separation

electrospun nanofiber

and organic-inorganic hybrid could construct more efficient ion transport channels

improving the ion conductivity of ICMs.