Proton Exchange Membrane for Iron Air/Flow Battery Application
Authors: Phela Manoko , Msomi Phumlani Fortune , Sigwadi Rhudzani 
Published: November 2022

Iron air/redox flow battery is the next promising battery system that can bridge the drawbacks of a static battery, at least in medium to high storage systems, due to the distinguishing difference from its static counterpart. It comes with the main advantages: the high current discharge and a flowing electrolyte, which can significantly suppress the formation of dendrite and passivation without imposing permanent damage to the cell structure. Iron, the fourth most abundant metal on the earth's crust, comes at a lower cost and requires less corrosion protection.
This technology has received less attention than others due to overpotential/overvoltage and high Hydrogen evolution reaction on the anode. Different promising approach has been explored to improve the cycling stability of iron air batteries; by adding different electrolyte additives to suppress passivation and hydrogen evolution during discharge, improving the air cathode design by including dual or bifunctional electrocatalyst, and recent modification of the anode has helped realize a better iron air battery by facilitating a high surface area iron electrode using nanosized iron particle, and these create more electrode available to electrolyte and further adding a suitable additive to the electrode and electrolyte and increase charge capacity.
Nonetheless, the battery working components begin to degrade as they interact; these cannot be stopped as batteries are consumable objects, but they can be delayed by improving the membrane separator's physical-chemical properties like conductivity, swelling ratio, selectivity, and membrane stability. Membrane's critical role aid in the improvement of the battery performance by separating the air cathode and metal anode electrode compartments to prevent short-circuiting, facilitate proton transfer, act as an electron insulator, and prevent fuel crossover, therefore improving the battery cycle life. The presentation will cover the basic working principle of the iron-air/redox flow battery and its prospective future in grid application and a brief report on the role of composite proton exchange membrane and their influence on cycle stability.
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