UNSW researchers cook up recipe for better, more sustainable batteries

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Researchers at the University of New South Wales (NSW) have developed a battery component using food-based acids that is found in off-the-shelf sherbet or winemaking.

UNSW School of Chemistry lead researcher Professor Neeraj Sharma said his team has developed an electrode that can significantly increase the energy storage capability of lithium-ion batteries by replacing graphite with compounds derived from food acids, such as tartaric acid, which occurs naturally in many fruits, and malic acid found in some fruits and wine extracts.

“Using food acids to produce water-soluble metal dicarboxylates – electrode materials – presents a competitive alternative to graphite used in the majority of lithium-ion batteries that can, as we’ve demonstrated, optimise battery performance, renewability and cost to better support battery demand,” Sharma said.

A prototype has been found to reduce environmental impacts across its materials and processing inputs while increasing energy storage capability and is a springboard to upscale the technology transitioning from a small coin cell to larger pouch cell capability.

“The next step will be running use/re-charge cycles at different temperatures to demonstrate industry viability and allow for further optimisation. The technology is also applicable to sodium-ion batteries that present another cheaper, greener alternative to lithium-ion batteries,” Sharma said.

The research has been driven by examining reported inconsistencies in food acid performance in the lab.

“Food acids are readily available, typically less aggressive and contain the necessary functional groups or chemical characteristics and the single-layer pouch cell currently being optimised is similar to what you’d use in a mobile phone, only smaller,” Sharma said.

“We realised the acid actually reacts with the metal surface of the battery component. It’s one of the first things we teach in first year chemistry – a metal plus an acid gives you a salt and hydrogen. And it’s that salt that’s now been stabilised that gives you that improved performance,” Sharma said.

“We experimented to understand what was happening, designing reactions to maximise performance and characterising the resulting compounds and their performance.”

“As a result, we have the versatility to change the combination to suit different supply streams and desired performance. For example, while we have got lots of iron in Australia, in other regions, manganese or zinc, for example, might be more accessible, and therefore these can be used as the metal component,” he said.

Professor Sharma is collaborating with another UNSW research team, that is pyrolyzing coffee grounds as a carbon source for lithium-sulphur battery anodes.

Image: ANTSO

Considering food waste as a source to formulate new electrode microstructures, the UNSW team have worked with colleague Professor Veena Sahajwalla who is pyrolyzing coffee grounds to use them as a carbon source to make anodes within lithium-sulphur batteries.

More than eight million tons of waste coffee grounds enter landfill globally every year, and food waste in Australia costs $36.6 billion (USD 25.1 billion) and is 3% of the country’s annual greenhouse gas emissions (GHG).

Recycling is a further motivator for Sharma’s team, who are researching a recyling process that doesn’t require harsh chemicals, but could potentially reuse the recycled waste material from current metal extraction processes.

“The remaining black mass is shipped offshore, to be dropped back down to its pure elements. We’re asking are there clever routes to reuse that mass in new batteries, minimising the chemicals involved, to create a closed loop,” Sharma said.

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