Batteries made from industrial waste could store renewable energy

Redox flow batteries offer a promising way to store power from wind and solar generation, and an industrial byproduct could be used in these batteries instead of lithium and cobalt, which are in short supply

By Matthew Sparkes

7 January 2025

A redox flow battery at a power plant in Japan. A new process could replace rare metals in these batteries with an industrial byproduct

Alessandro Gandolfi/Panos Pictures

An industrial waste product has been converted into a component for batteries that can stably store large amounts of charge. Such batteries could perform a vital function for power grids by smoothing out the peaks and troughs of renewable energy.

Redox flow batteries (RFBs) store 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 and produce electrons to generate energy. The process can be reversed to recharge the battery by placing a current across the membrane.

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Such batteries are cheap, but they have downsides. They are bulky, often as big as a shipping container, and require constant maintenance because of the moving parts involved in pumping the liquid. They also rely on metals like lithium and cobalt, which are in short supply.

Now, Emily Mahoney at Northwestern University in Evanston, Illinois, and her colleagues have discovered a simple process that can turn a previously useless industrial waste product into a useful anolyte, which could potentially replace these rare metals.

Their process takes triphenylphosphine oxide, created in the manufacture of products including vitamin tablets, and converts it into cyclic triphenylphosphine oxide, which has a high potential for storing negative charge. When used as an anolyte, it shows no reduction in effectiveness even after 350 charging and draining cycles.