A Titanium Manganese Redox Flow Battery-Electrolyser with Lead-Dioxide Positive Electrode

Redox flow battery electrolysers can act as both batteries for long-duration energy storage and as electrolysers for the production of hydrogen and oxygen. The hydrogen is an additional energy storage vector whose production can make use of renewable electricity generation that would otherwise be curtailed. This paper presents a titanium-manganese redox flow battery electrolyser. Charging and electrolysis functions use one cell stack with lead dioxide positive plates to withstand the high voltages and highly acidic conditions. Discharging takes place in a second cell stack using electrodes made of low-cost carbon materials. The charging cell exhibits good Faradic efficiency when fully charged and operating as an electrolyser (near 100%) but only poor efficiency when cycling as a redox flow battery (17%). This technology could be combined with a lead-acid battery-electrolyser so that the energy capacity and duration of electricity storage can be expanded independently of power rating. The combined device can be fully discharged, fully charged, over-charged and indefinitely cycled without oxidation imbalance. Five cycles have been demonstrated in the laboratory, each consisting of 17 hours charging and 5 hours discharging. The raw materials are cheaper and have lower environmental impact than the market leading all-vanadium redox flow batteries.