The recipe for sustainable battery recycling

Researchers at Chalmers University of Technology, in Sweden, have discovered a new way to recycle metals from spent electric car batteries. The method allows recovery of 100% of the aluminium and 98% of the lithium in electric car batteries, minimising the loss of nickel, cobalt and manganese. The process uses oxalic acid from plants, requiring no expensive or harmful chemicals.

Léa Rouquette, PhD student at the Department of Chemistry and Chemical Engineering, said this process is the first of its kind to find the right conditions to separate this much lithium using oxalic acid while also removing all the aluminium.

In Chalmers’ battery recycling lab, Rouquette and Martina Petranikova, research leader, showed how the method works. The lab has spent car battery cells and their pulverised contents, which takes the form of a finely ground black powder dissolved in oxalic acid. Rouquette produces both the powder and the liquid in something reminiscent of a kitchen mixer. Although it looks as easy as brewing coffee, the exact procedure is unique. By fine-tuning temperature, concentration and time, the researchers have come up with a recipe for using oxalic acid — an environmentally friendly ingredient that can be found in plants such as rhubarb and spinach.

Petranikova said there is need for alternatives to inorganic chemicals. In today’s processes, a major bottleneck is removing residual materials like aluminium. This method can offer the recycling industry new alternatives, helping to solve problems that hinder development.

The aqueous-based recycling method is called hydrometallurgy. Traditionally, all the metals in an EV battery cell are dissolved in an inorganic acid, then all impurities such as aluminium and copper are removed. Lastly, the valuable metals such as cobalt, nickel, manganese and lithium are recovered. Even though the amount of residual aluminium and copper is small, it requires several purification steps and each step in the process can cause lithium loss. With the new method, the researchers reverse the order and recover the lithium and alluvium first, reducing the waste of valuable materials which can be used to make new batteries.

The latter part of the process sees the black mixture filtered. While aluminium and lithium end up in the liquid, the other metals are left in the ‘solids’. The next step in the process is to separate aluminium and lithium.

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

“As the method can be scaled up, we hope it can be used in industry in future years,” Petranikova said.

Petranikova’s research group has spent many years conducting research in the recycling of metals found in lithium-ion batteries. The group is involved in various collaborations with companies to develop electric car battery recycling and is a partner in major research and development projects, such as Volvo Cars’ and Northvolt’s Nybat project.

Image: Chalmers University of Technology/Anna-Lena Lundqvist