Researchers in the UK have found a way to enhance hybrid flow batteries and drastically reduce the potential cost of stationary storage systems to as low as £15 ($20) per kilowatt hour.
The team from WMG at the University of Warwick, in collaboration with Imperial College London, enhanced three hybrid flow cells— developed by Imperial’s spin-out company RFC Power— using nitrogen doped graphene (exposed to nitrogen plasma) in a binder-free electrophoresis technique (EPD).
EPD involves the migration of electrically charged particles through a fluid that is under the influence of an electric field generated by applying the right potential.
The cost of the flow battery could be a game changer for stationary applications as the US Department of Energy suggests an affordable grid battery should cost £75/kWh ($102/kWh)— lithium-ion batteries cost around £130/kWh ($177/kWh).
The new system could cost around £15 ($20) to £20 ($27) per kilowatt hour.
The technology combines carbon-based electrodes with manganese or sulphur electrolytes by means of electrophoretic deposition of nano-carbon additives (nitrogen-doped graphene). The method enhances the electrode durability and performance in highly acidic or alkaline environments.
The findings were published in a paper entitled ‘Hybrid Redox Flow Cells with Enhanced Electrochemical Performance via Binderless and Electrophoretically Deposited Nitrogen-Doped Graphene on Carbon Paper Electrodes’ in the journal ACS Applied Materials & Interfaces.
Dr Barun Chakrabarti, a Research Fellow in WMG at the University of Warwick and one of the lead authors on the paper, said: “This EPD technique is not only simple but also improves the efficiencies of three different economical hybrid flow batteries thereby increasing their potential for widespread commercial adoption for grid-scale energy storage.”
These batteries are useful for grid-scale, load-levelling applications.
The energy density of a hybrid flow battery, especially the polysulphide/air system (S-Air), is 500 times higher than pumped hydroelectric storage, say the researchers.
Development of the EPD technology began in 2013 when professor John Low joined WMG as an assistant professor and researched industrial lithium-ion battery manufacturing processes.