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Abstract

In order for the widely discussed advantages of redox flow batteries for electric energy storage (EES) system to be at large scale, the cost of the electrochemical stack must decrease to be developed practically. Among them, aqueous zinc-bromine redox flow batteries (ZBBs) had much attention due to its high open circuit voltage (1.82 V), theoretical energy (> 400 W h kg-1) and inexpensive redox active materials. However, no single-cell ZBBs has met the cost, lifetime, and performance targets required for successful EES system. Herein, we report membraneless, non-flowing Zn/Br battery by using nitrogen (N) doped microporous carbon electrode. Through a combination of N-doped and microporous carbon surface of positive electrode, it confirmed that well conversion of corrosive elemental bromine to polybromide anion and then strongly binds within the N-doped microporous carbon electrode. Conversion and storaging of bromine in polybromide anion form within the electrode were investigated using spectroscopic analysis and density functional theory calculation. Membrane-free battery enables energy efficiencies of 80% for over 1,000 cycles even without separator, bromine sequestration agent and supporting electrolyte.