A highly stable membrane with hierarchical structure for wide pH range flow batteries

Abstract A membrane with high stability and ion conductivity in wide pH range is essential for energy storage devices. Here, we report a novel membrane with hierarchical core-shell structure, which demonstrates high stability and ion conductivity, simultaneously under a wide pH range applications. Spectral characterizations and theoretical calculation indicate that the non-solvent induces the chain segment configuration and eventually leads to polymer-polymer phase separation, thus forming hierarchical porous core-shell structure. Benefiting from this structure, an acidic vanadium flow battery (VFB) with such a membrane shows excellent performance over 400 cycles with an energy efficiency (EE) of above 81% at current density of 120 mA cm-2 and an alkaline zinc-iron flow battery (AZIFB) delivers a cycling stability for more than 200 cycles at 160 mA cm-2, along with an EE of above 82%. This paper provides a cost-effective and simple way to fabricate membranes with high performance for variety of energy-related devices.