With global demand for lithium-ion batteries fast depleting reserves of raw materials, experts are seeking safe, affordable and reliable alternatives for rechargeable batteries.

Aqueous zinc-ion batteries (AZIBs) could be the answer to producing low-cost alternatives from abundant feedstocks, and Flinders University scientists are paving the way for the production of simple and practical polymer AZIBs using organic cathodes for more sustainable energy storage technology.

"Aqueous zinc-ion batteries could have real-world applications," says Associate Professor of Chemistry Zhongfan Jia, a nanotech researcher at the College of Science and Engineering at Flinders University.

From electric vehicles to portable electronic devices, the demand and consumption of lithium-ion batteries (LIBs) have led to resource shortages and supply-chain issues of strategic metals including lithium and cobalt.

Meanwhile, millions of spent batteries, most of which are not properly recycled, have caused enormous waste and environmental risks—which future alternatives such as AIZBs promise to reduce.

"Among these alternatives, AZIBs stand out because of the much higher abundance of zinc in the earth's crust (10 times more than lithium), and their low toxicity and high safety."

AZIBs usually use zinc metal as an anode and inorganic or organic compounds as a cathode. While substantial work has been devoted to improving the stability of zinc anodes, high-performing cathodes are needed and remain a major challenge.

"Our research is building conductivity using nitroxide radical polymer cathodes made from cheap commercial polymer and optimized the battery performance using low-cost additives," says Associate Professor Jia, who leads a research group working on Sustainable Polymers for Energy and Environment.

"Our work reevaluated the use of high redox potential nitroxide radical polymers cathodes in AZIBs, and produced the highest mass loading so far," he says, about a new online journal article in the Journal of Power Resources.

The study, led by Flinders master student Nanduni Gamage and postdoc fellow Dr. Yanlin Shi, developed a lab-made pouch battery using scaled-up polymer (at approx. cost $20 / kg), a non-fluoro Zn(ClO₄)₂ electrolyte, and BP 2000 carbon black ($1 / kg) without binder to provide a capacity of nearly 70 mAh g^-1 and a middle discharge voltage of 1.4 V.

"Morphological engineering of PTAm@CNTs cathode for high-rate potassium dual-ion battery" has been published in the Journal of Power Resources and "Converting a low-cost industrial polymer into organic cathodes for high mass-loading aqueous zinc-ion batteries" has been published in Energy Storage Materials.

With a mass loading of 50 mg cm^-2, the pouch battery had a capacity of 60 mAh, which can easily power a small electric fan and a model car.

Collaborators in the study, including Dr. Jesús Santos-Peña, from the Université Paris Est Creteil CNRS in France, and other experts from the Flinders University Institute for Nanoscale Science and Technology.

In collaboration with Griffith University, the team has also recently developed organic radical/K dual-ion batteries, a technique that can also relieve dependence on lithium-ion batteries.