J. Huang, G.G. Yadav, S. Banerjee
Urban Electric Power Inc.,
Keywords: zinc, manganese dioxide, alkaline, graphene oxide, separator
Summary:Rechargeable alkaline Zn/MnO2 battery is currently an attractive candidate for grid-scale energy storage due to its low cost, safety characteristics, and high gravimetric capacity. However, a long cycle life is only achievable with restricted depth of discharge (DOD). One of the major factors that limit its rechargeability is the poisoning effect caused by the zincate ions. Zincate is the soluble discharge product of a Zn anode. It traverses to the cathode compartment during discharge and reacts to form a highly resistive and electrochemically inactive spinel phase (ZnMn2O4), which leads to rapid energy density loss and battery failure. Therefore, inhibiting ZnMn2O4 formation remains a major challenge for the long-term cycling of an energy dense Zn/MnO2 battery. In this talk, we report a zincate blocking membrane with two-dimensional graphene oxide (GO) sheets as the main building blocks. A water-soluble polymer poly(vinyl alcohol) (PVA) is also introduced to modify the membrane’s physicochemical properties. The structure of the membrane is characterized, and its selectivity towards zincate ions is investigated. We demonstrate the superiority of the GO-based membrane in suppressing zincate ion crossover while minimally impairing hydroxide conduction, and report near full utilization of MnO2 electrode’s 2-electron capacity (~617 mAh/g-MnO2) both in a primary cell setup for a single discharge and in a secondary cell setup for more than 300 cycles.