New cathode chemistry slashes self-discharge in grid-scale zinc-iodine batteries

The formula powering aqueous zinc-iodine batteries has been brought under the microscope, with researchers from the University of Adelaide finding a way to enhance their performance.

Rechargeable aqueous zinc batteries are growing as potential replacements for large energy storage systems made of lithium-ion for its low cost, affordable density and high safety.

However, the conventional hosts for iodine cathodes often show slow reactions and poor electrochemical reproducibility, so the research team, led by Professor Shizhang Qiao, Chair of Nanotechnology at the School of Chemical Engineering, sought to use ferrocene in the cathodes.

Their findings were published in the journal Nature Chemistry.

“The conversion of iodine in aqueous zinc-iodine batteries accompanies the polyiodides shuttle effect, but the conversion of ferrocene, an organometallic compound, can precipitate the polyiodides which gives it a low self-discharge,” says Professor Qiao, who is also the Director, Center for Materials in Energy and Catalysis.

“Since ferrocene is composed of low-cost elements, it offers favorable scalability and potentially low cost for large-scale production.

“Simulation results show that incorporating it reduces the total battery cost by 9% compared to that without ferrocene.”

Professor Qiao said use of ferrocene essentially eliminated the shuttle effect, a problem common in zinc-iodine batteries, where intermediate polyiodides dissolve in the electrolyte and shuttle back and forth between the cathode and anode.

“Not only does using ferrocene improve energy density but it also lowers the overall cost, making the coupling a practical, economical, and scalable strategy for advancing aqueous zinc-iodine battery technologies,” says Professor Qiao.

“Our findings also show the active mass in the cathode can reach 88%, minimizing the capacity loss of inactive hosts.”