A redox flow battery at a power plant in Japan. New process could replace rare metals in these batteries with industrial byproducts
Photo by Alessandro Gandolfi/Panos
Industrial waste has been reborn as a battery component that can stably store a large amount of electrical charge. Such batteries could serve an important function for the power grid by smoothing out the peaks and valleys of renewable energy.
A redox flow battery (RFB) stores energy as two liquids called an anolyte and a catholyte in a pair of tanks. When these fluids are pumped into a central chamber separated by a thin membrane, they chemically react to generate electrons and generate energy. This process can be reversed to recharge the battery by passing an electric current through the membrane.
Although such batteries are cheap, they also have drawbacks. They are bulky, often as large as shipping containers, and require regular maintenance because they involve moving parts in pumping liquids. It also relies on metals such as lithium and cobalt, which are in short supply.
now, Emily Mahoney and colleagues at Northwestern University in Evanston, Illinois, have discovered a simple process that can turn previously useless industrial waste into useful anolyte. This could potentially replace these rare metals.
Their process converts triphenylphosphine oxide, which is produced during the manufacture of products such as vitamin tablets, to cyclic triphenylphosphine oxide, which is more likely to accumulate negative charges. When used as an anolyte, no loss of effectiveness is observed after 350 charging and draining cycles.
“Using an anolyte with a very negative potential increases the potential across the cell and therefore increases the efficiency of the battery,” Mahoney says. “But often the increased potential comes with stability issues, so it's exciting to have a stable yet highly negative compound.”
Mahoney said RFBs are designed to be safe and high-capacity, so they could potentially be used to store energy from wind and solar power, but their bulk makes them unsuitable for lithium-ion batteries in cars and smartphones. It is unlikely that they will be replaced.
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Source: www.newscientist.com
