Researchers at Chalmers University of Technology in Gothenburg in Sweden have discovered a new method of recycling used lithium batteries.
The problem with depleted EV batteries is that the black mass – the residue of the battery cell contents – is a complex mixture of chemical substances, e.g. lithium, aluminum, nickel and cobalt. To separate the valuable parts from the residue, the research team at Chalmers have used a very common chemical agent, oxalic acid, which is naturally found in rhubarb and spinach. The aqueous-based recycling method is a hydrometallurgical process.
Traditionally all the metals in an EV battery cell are dissolved in an inorganic acid. Then, you remove the “impurities” such as aluminum and copper. Lastly, you can separately recover valuable metals such as cobalt, nickel, manganese, and lithium. The method requires several purification steps causing possible lithium loss. With the new method lithium and aluminum are recovered first, reducing the waste of valuable metals. The black powder is diluted in oxalic acid and then filtered; a bit reminiscent of brewing coffee. While aluminum and lithium end up in the liquid, the other metals are left in the “solids”. The next step in the process is to separate aluminum 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 warrants further exploration,” says Léa Rouquette, PhD student at Chalmers.
“We need alternatives to inorganic chemicals. One of the biggest bottlenecks in today’s processes is removing residual materials like aluminum. This innovative method can offer the recycling industry new alternatives,” says Martina Petranikova, Associate Professor at the Department of Chemistry and Chemical Engineering at Chalmers. “As the method can be scaled up, we hope it can be used in the industry in future years.”