Lithium-ion batteries could soon be replaced as the power source of choice in electronic devices as researchers have discovered how to build rechargeable zinc-air batteries.

Zinc-air batteries are batteries powered by zinc metal and oxygen from the air, which, thanks to the global abundance of zinc metal, are much cheaper to produce than lithium-ion batteries and can also theoretically store five times more energy than that of lithium-ion batteries.

Zinc-air batteries are also much safer and more environmentally friendly.

However, their widespread use has been hindered by the fact that, up until now, recharging them has proved difficult. This is due to the lack of electrocatalysts that successfully reduce and generate oxygen during the discharging and charging of a battery.

In the journal Advanced Materials, researchers from the University of Sydney have outlined a new three-stage method to overcome this problem.

“Up until now, rechargeable zinc-air batteries have been made with expensive precious metal catalysts, such as platinum and iridium oxide. In contrast, our method produces a family of new high-performance and low-cost catalysts,” said the study’s lead author Professor Yuan Chen, from the University of Sydney’s Faculty of Engineering and Information Technologies.

University of Sydney researchers used a new method – creating bifunctional oxygen electrocatalysts – which allowed them to build rechargeable zinc-air batteries from scratch.

The researchers also replaced precious metal catalysts with low cost variations, which were produced through the simultaneous control of the composition, size and crystallinity of metal oxides in earth-abundant elements such as iron, cobalt and nickel.

The study’s co-author Dr Li Wei, also from the University’s Faculty of Engineering and Information Technologies, said trials of zinc-air batteries developed with the new catalysts had demonstrated excellent rechargeability – including less than a 10% battery efficacy drop over 60 discharging and charging cycles of 120 hours.

“We are solving fundamental technological challenges to realise more sustainable metal-air batteries for our society,” Chen added.