Researchers at Chalmers University of Technology, Sweden, are presenting a new and efficient way to recycle metals from spent electric car batteries. The method, which uses the organic acid oxalic acid, allows recovery of 100% of the aluminum and 98% of the lithium in electric car batteries. At the same time, the loss of valuable raw materials such as nickel, cobalt and manganese is minimized. An open-access paper on the method is published in the journal Separation and Purification Technology.

Rouquette et al.

Currently, there are two main families of recycling processes. Historically, pyrometallurgy is a well-settled process, capable of handling large volumes and inhomogeneous feed material, but this goes along with gas emission and high energy consumption. Moreover, the lithium is lost as it ends up in the slag after the treatment along with aluminum and manganese.

Research is ongoing for its recovery from the slag using hydrometallurgy, but a feasible process is not expected in the upcoming years. On the other hand, hydrometallurgy allows to achieve higher recovery rates and requires lower energy consumption, but it is a more complex and chemically intensive process.

A traditional flowsheet starts with the dissolution of valuable metals from the black mass during an acidic leaching operation assisted with a reducing agent such as hydrogen peroxide, followed by separation steps where the metals can be selectively recovered one after the other using solvent extraction or precipitation. Finally, purification technologies are needed to obtain products that can be reintegrated into the battery production. Some robust processes already exist but lithium is very little recovered and suffers losses all along the recycling process since its recovery is commonly addressed at the end of the recycling circuit.

In this work, the feasibility of an early selective and complete recovery of lithium by leaching with oxalic acid was investigated using a black mass sample from spent EV batteries (which was industrially produced using crushing and mechanical sorting). A design of experiments was used to define the best operating conditions, which were validated with a scale-up of the operation under optimal conditions. The objective was to optimize the acid consumption and to define the mechanism of the leaching process using oxalic acid.

Lithium was separated from the rest of the valuable elements, cobalt, nickel, and manganese as their respective oxalate without any addition of reductant. This selective lithium recovery with a reduction of impurities in the leachate is the main achievement of this study.

—Roquette et al.

By fine-tuning temperature, concentration and time, the researchers coame up with a new recipe for using oxalic acid—an environmentally friendly ingredient that can be found in plants such as rhubarb and spinach.

We need alternatives to inorganic chemicals. One of the biggest bottlenecks in today’s processes is removing residual materials like aluminum. This is an innovative method that can offer the recycling industry new alternatives and help solve problems that hinder development.

—Martina Petranikova, Associate Professor at the Department of Chemistry and Chemical Engineering at Chalmers

In traditional hydrometallurgy, 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. Even though the amount of residual aluminum and copper is small, it requires several purification steps and each step in this process can cause lithium loss. With the new method, the researchers reverse the order and recover the lithium and aluminum first. Thus, they can reduce the waste of valuable metals needed to make new batteries.

The research 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.

The research was funded by the Swedish Energy Agency (52009-1), BASE Batteries Sweden, Vinnova (2019-00064) and the experiments were conducted with spent electric car batteries from Volvo Cars, processed by Stena Recycling and Akkuser Oy.

Resources

• Léa M.J. Rouquette, Martina Petranikova, Nathália Vieceli (2023) “Complete and selective recovery of lithium from EV lithium-ion batteries: Modeling and optimization using oxalic acid as a leaching agent,” Separation and Purification Technology, Volume 320, doi: 10.1016/j.seppur.2023.124143.