Hybrid flow batteries modified to enhance efficiency

UK researchers have found a way to enhance hybrid flow batteries, utilising nitrogen-doped graphene (exposed to nitrogen plasma) in a binder-free electrophoresis technique (EPD). Described in the journal ACS Applied Materials & Interfaces, the new approach can store electricity in these batteries for very long durations for about 20% of the price of current technologies, with minimal location restraints and zero emissions.

Wind and solar power are increasingly popular sources for renewable energy, but intermittency issues keep them from connecting widely to the national grid. One potential solution to this problem involves the deployment of long-duration battery technology, such as the redox flow battery, but the current costs of this system are a key determining factor to real-world adoption. An affordable grid battery should cost £75/kWh, according to the US Department of Energy; lithium-ion batteries, which lead the charge for grid storage, cost about £130/kWh.

Researchers from WMG at the University of Warwick, in collaboration with Imperial College London, have now found a way of enhancing hybrid flow batteries or regenerative fuel cell (RFC) technology that could store electricity for very long durations for about one-fifth the cost of current storage technologies, with flexibility in siting and with minimal environmental impact. Their technology combines carbon-based electrodes with economically sourced electrolytes (manganese or sulfur, which are abundant chemicals in the planet) by means of a simple and yet highly effective electrophoretic deposition of nano-carbon additives (nitrogen-doped graphene) that enhance the electrode durability and performance significantly in highly acidic or alkaline environments.

The hybrid flow battery’s total chemical cost is about 1/30th the cost of competing batteries, such as lithium-ion systems. Scaled-up technologies may be used to store electricity from wind or solar power, for multiple days to entire seasons, for about £15 to £20/kWh. The batteries are also useful for grid-scale load levelling applications as their design is very flexible, due to the fact that they size their power independently of their energy.

“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,” said WMG Research Fellow Dr Barun Chakrabarti, a lead author on the paper.

Image credit: ©stock.adobe.com/au/corund

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