Cheaper, cleaner and with five times more energy: Researchers discover new method for building zinc-air batteries

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.

Featured image courtesy of the University of Sydney

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.

The ocean is the answer to future food security but we’re not using it: scientists

The vast majority of coastal countries on Earth are missing out on a valuable resource to ensure future food security, according to newly published research.

Published in the journal Nature Ecology and Evolution, the research has found that the world’s oceans contain numerous “hot spots” for marine aquaculture, or ocean-based fish farms, which could produce 15 billion tonnes of fish every year: over 100 times current seafood consumption globally.

“There are only a couple of countries that are producing the vast majority of what’s being produced right now in the oceans,” said lead author Rebecca Gentry, from UC Santa Barbara’s Bren School of Environmental Science and Management. “We show that aquaculture could actually be spread a lot more across the world, and every coastal country has this opportunity.”

However, an unwillingness by governments to seriously explore aquaculture could seriously jeopardise this.

“There is a lot of space that is suitable for aquaculture, and that is not what’s going to limit its development,” said Gentry. “It’s going to be other things such as governance and economics.”

A fish farm in Dugi Otok, Croatia

At present, many countries choose to import much of their seafood, despite significant potential to meet their own needs.

The US, for example, imports over 90% of its fish, resulting in a trade deficit for seafood alone that tops $13bn. However, it could produce its entire domestic supply using just 0.01% of its ocean territory.

Worldwide, the story is similar: aquaculture could match the entire seafood production of every wild-caught fishery using a combined area the size of Lake Michigan: less than 1% of the total ocean surface.

And with food security under increasing threat, it is only a matter of time before countries take aquaculture seriously.

“Marine aquaculture provides a means and an opportunity to support both human livelihoods and economic growth, in addition to providing food security,” said co-author Ben Halpern, executive director of the National Center for Ecological Analysis and Synthesis (NCEAS). “It’s not a question of if aquaculture will be part of future food production but, instead, where and when. Our results help guide that trajectory.”

Cages used in marine aquaculture

With such potential, it is no surprise that aquaculture is already on the increase.

“Aquaculture is expected to increase by 39% in the next decade,” said study co-author Halley Froehlich, a postdoctoral researcher at NCEAS. “Not only is this growth rate fast, but the amount of biomass aquaculture produces has already surpassed wild seafood catches and beef production.”

However, if aquaculture is going to be a core part of future food production, it needs to be managed properly, something that hasn’t always happened in the past. In the 90s, the poor management of shrimp farming in Thailand led to a boom and bust that left vast coastal areas barren.

“Like any food system, aquaculture can be done poorly; we’ve seen it,” said Froehlich. “This is really an opportunity to shape the future of food for the betterment of people and the environment.”