New spin on EV battery recycling plants

A new study out of Chalmers University of Technology, Sweden, presents a possible new and efficient way to recycle metals from spent electric vehicle batteries that uses an organic compound found naturally in plants – oxalate.

Before the push for clean energy or renewable technologies, methods to recycle metal operated much like manufacturing metal, melting it. However, due to the carbon-intensive impacts of smelters or foundries, cleaner solutions to recycling have exploded on the scene.

Solvometallurgy, hydrometallurgy, and electrometallurgy are some of the growing techniques scientists, researchers, and businesspeople have been exploring to reclaim as much material as possible without waste and pollution.

While great strides have been made with nearly 100% reclamation of materials, inevitable degradation or reduction of the metals and minerals used in batteries and other applications has not yet been perfected.

In pursuit of a viable solution that does not rely on chemicals that contribute to a higher carbon footprint, researchers from Chalmers sought something found in abundance in the plant kingdom: oxalate, otherwise known as oxalic acid.

Now, acids used to break down materials are not a new concept; however, like melting recyclables, acids are not specific in what they break down. Clever chemistries have narrowed down what is and isn't separated but remain unperfected.

The growing popularity of hydrometallurgy, an aqueous-based recycling method that dissolves battery cells in inorganic acid, is a leading contender for maximizing recycling. However, even this highly precise chemical process leaves behind residual quantities of aluminum and copper, which requires further purification steps that lead to lithium loss with each additional step.

Ultimately, this reduces the final total of materials needed in new batteries, especially during a time when demand has never been higher and supply cannot keep up.

"So far, no one has managed to find the right conditions for separating this much lithium using oxalic acid, whilst also removing all the aluminium," said Léa Rouquette, a Ph.D. student at the Department of Chemistry and Chemical Engineering at Chalmers. "Since all batteries contain aluminium, we need to be able to remove it without losing the other metals."

Their new method purportedly allows for the recovery of 100% of the aluminum and 98% of the lithium in EV batteries while simultaneously minimizing the loss of valuable raw materials such as nickel, cobalt, and manganese.

And it's largely available everywhere there are plants.

Oxalic acid

Oxalic acid is an organic compound found naturally in many plants, such as leafy greens, vegetables, fruits, nuts, seeds, fungi, etc. For our green friends, oxalate functions as a calcium regulator, a defensive system against insects or grazing animals, or for detoxification.

This is essentially a pH dial in plants that can regulate their health as well as destabilize foreign invaders.

Outside of flora uses, oxalic acid is often called an anti-nutrient. Due to its ability to bind with certain minerals, such as calcium or iron, it becomes a new compound and is lost upon excretion, thus losing its initial benefits.

Aside from ingestion, oxalic acid has found numerous uses in industry. These include rust removal, stain removal, stripping and cleaning, wax removal, wood cleaner, and dyeing textiles. Laboratories may also use oxalic acid and oxalate salts as anticoagulants in blood specimens.

In Chalmers' battery recycling lab, Rouquette and research leader Martina Petranikova demonstrate how their new method with this organic acid works.

Using a conventional spent EV battery cell, they grind it up until it becomes a finely ground black powder. This is not unlike larger facilities that grind the recycled product into black mass.

Afterward, they take the powder and dissolve it in oxalic acid. While the research team made it look as easy as brewing a pot of coffee, simply mixing them together in something reminiscent of a kitchen mixer, Chalmers says the exact procedure is a unique and recently published scientific breakthrough.

By fine-tuning temperature, concentration, and timing, the scientists have come up with a remarkable new recipe for using oxalic acid.

"We need alternatives to inorganic chemicals," said Martina Petranikova, associate professor at the Department of Chemistry and Chemical Engineering at Chalmers. "One of the biggest bottlenecks in today's processes is removing residual materials like aluminium. This is an innovative method that can offer the recycling industry new alternatives and help solve problems that hinder development."

Recipe for success

With the groundwork already built using inorganic acids in present hydrometallurgical processes, an even more effective – practical- and cost-wise – acid may be just what renewable recyclers need to make their operations more economical.

Through Chalmers' new method, the researchers ultimately reversed the order of dissolving then purifying, which saves on lost material that may not seem like much, but over years or decades and tens of thousands to hundreds of thousands of batteries, it adds up.

Once ground up, the latter part of the process ends up filtered into the remaining liquid, while the other metals are left in the "grounds." The next step would be a separation of aluminum and lithium instead of the rare materials after the fact.

"Since the metals have very different properties, we don't think it'll be hard to separate them," said Rouquette. "Our method is a promising new route for battery recycling – a route that definitely warrants further exploration."

Spending many years conducting cutting-edge research in the recycling of metals found in lithium-ion batteries through various collaborations with companies to further develop EV battery recycling capabilities, such as Volvo and Northvolt, Petranikova's research group is certain this will bring a sweeping change for future recyclers.

"As the method can be scaled up, we hope it can be used in industry in future years," added Petranikova.