Next-gen batteries using food-based acids hit sustainability sweet spot

A novel battery component that uses food-based acids found in sherbet and winemaking could make lithium-ion batteries more efficient, affordable and sustainable, according to new research out of UNSW.

A prototype, developed and patented by UNSW chemists, reduces environmental impacts across its materials and processing inputs while increasing energy storage capability.

UNSW Science lead researcher Professor Neeraj Sharma says the research team is optimising a single-layer pouch cell, similar to what you’d use in a mobile phone, only smaller.

“We’ve 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 [that occurs naturally in many fruits] and malic acid [found in some fruits and wine extracts],” he said.

These food acids are readily available, typically less aggressive and contain the necessary functional groups or chemical characteristics.

“[Our battery component] could potentially use food acids from food waste streams, [reducing their environmental and economic impact],” Professor Sharma said.

“Its processing uses water rather toxic solvents, so we’re improving the status quo across multiple areas.

“By using waste produced at scale for battery components, the industry can diversify their inputs while addressing both environmental and sustainability concerns.

“Our focus is to really understand the materials [used in batteries] and their mechanism during battery operation and using this understanding we can design better materials.

“Our research ranges from synthesizing new materials, characterising new and commonly used materials and devices, to recycling and end-of-life degradation challenges.”

Professor Sharma says the need for batteries has only increased in recent years as we continue to develop renewable energy infrastructure.

“This is because replacing fossil fuel-based energy sources with renewable energy sources — for example, wind or solar — is contingent on our ability to store this energy that is generated intermittently,” he said.

“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.”

Current technological limitations demand innovation

Lithium-ion batteries make up the majority of our household and grid stationary battery energy storage to store excess solar energy.

However, Professor Sharma says the limitations of current technologies — relatively low storage capacities, expensive and environmentally unfriendly processes and inaccessible materials — are slowing down battery uptake.

Lithium-ion batteries predominantly use graphite anodes, conventionally termed the negative side of the battery. Graphite sources are relatively inaccessible and require mining, purifying and processing.

Professor Sharma says about 60% of the graphite is lost in the processing steps, which typically require high temperatures and very strong acids to reach the required purity, leading to a large environmental footprint.

“By understanding the chemistry of batteries, we can enhance their physical properties and improve their energy storage capacity [to hold more power], ionic conductivity [enabling higher rates of energy discharge or re-charge] or structural stability [extending their lifespan to improve sustainability],” he 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.

“It’s that salt [that’s now been stabilised] that gives you that [improved] performance.

“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.”

The team are currently upscaling the technology, increasing production quantities, and transitioning from 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.

The future of batteries is… coffee?

Professor Sharma says the research team is looking at diverting diverse bio-waste streams from landfill to use them as sources to formulate new electrode microstructures.

“For example, we’ve worked with Professor Veena Sahajwalla to pyrolyse coffee grounds to [use them as a carbon source to] make anodes within lithium-sulphur batteries,” he said.

The end-of-life cycle for batteries — how they degrade, safety and sustainability considerations — is also a significant concern.

Professor Sharma says recycling is a significant challenge.

“In ten to twenty years, we’re going to have a huge amount of the batteries from electric vehicles, scooters, power tools and household and grid storage possibly coming offline,” he said.

“At the moment, the [associated recycling] process is very energy-intensive, using harsh chemicals.

“Samsung batteries can be chemically very different to LG batteries to Tesla/Panasonic batteries, but they put them all together, grind them up and extract the metals — the stainless steel, copper and aluminium.

“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].

“It’s about having different battery technologies for different applications, including bringing solar and battery power together in one device.

“And asking how we can input more sustainable processes, use more sustainable materials to make it cheaper, better, faster, safer.”