The process, which aims to solve bottlenecks and wastage in EV battery recycling – an important factor in their sustainability – was developed at Chalmers University of Technology in Sweden.
The method also minimises the loss of valuable raw materials such as nickel, cobalt and manganese, the research announcement said. No expensive or harmful chemicals are required in the process because the researchers use oxalic acid – an organic acid that can be found in plants such as rhubarb and spinach.
“So far, no one has managed to find exactly the right conditions for separating this much lithium using oxalic acid, whilst also removing all the aluminium. Since all batteries contain aluminium, we need to be able to remove it without losing the other metals,” said Léa Rouquette, PhD student at Chalmers.
In the university laboratory, the pulverised contents of used car battery cells, which takes the form of a finely ground black powder, is dissolved in the acid. By fine-tuning the temperature, concentrations and time taken, the researchers say their new process has provided “remarkable” results.
“We need alternatives to inorganic chemicals. 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,” said Martina Petranikova, associate professor at Chalmers.
The aqueous-based recycling method is called hydrometallurgy. In traditional hydrometallurgy, all the metals in an EV battery cell are dissolved in an inorganic acid. The ‘impurities’ such as aluminium and copper are then removed, followed by separate recovery of valuable metals such as cobalt, nickel, manganese and lithium. Even though the amount of residual aluminium and copper is small it requires several purification steps, the researchers said, and each step in this process can cause lithium loss.
With the new method, the researchers reverse the order and recover the lithium and aluminium first. The mixture of pulverised waste and oxalic acid is filtered, leaving aluminium and lithium in the liquid and other metals in the solid.
This reduces the waste of valuable metals needed to make new batteries, the researchers said.
The next step in the process is to separate the 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,” said Rouquette.
“As the method can be scaled up, we hope it can be used in industry in future years,” added Petranikova.
The group is involved in various collaborations with companies to develop EV battery recycling. It is a partner in major R&D projects, such as Volvo and Northvolt's Nybat project.
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