Black mass is the powdered material resulting from shredding end-of-life lithium-ion vehicle batteries. For effective recycling, lithium must be efficiently separated from this material, but conventional methods, such as smelting at high temperatures or dissolving in strong acids, require large amounts of energy and chemicals, and generate substantial volumes of liquid waste.
Now, researchers at Rice University (Houston, Tex.; www.rice.edu) have taken a step toward a lower-energy and more environmentally friendly method with an electrochemical approach that uses the battery’s own chemistry to isolate lithium in a form (highly pure LiOH) that can be reused in new batteries.
“We essentially ‘recharge’ the cathode materials… prompting them to release Li,” the researchers say. By pairing this reaction with simple processes, like splitting water, the team directly produced LiOH, a highly pure raw material for making new batteries. “The process only needs electricity, water and the battery waste itself, without harsh chemicals,” the Rice team says.
By leveraging the intrinsic delithiation chemistry of battery cathode materials as a separation mechanism, the researchers created a more sustainable, scalable and cost-effective approach. They devised a zero-gap membrane electrode assembly (MEA) reactor to recover lithium from black mass that came from end-of-life LiFePO4 (LFP) batteries.
The team reports that its method achieved a Faradaic efficiency of 96.4% for lithium extraction, yielding high-purity (around 99.0 wt. %) LiOH. Also, the energy consumption was reduced to as low as 103 kJ per kg of black mass. A 20-cm2 MEA reactor built by the Rice research team, along with partner TotalEnergies (Corbevoie, France; www.totalenergies.com), demonstrated stable operation for 1,000 h, processing about 57 g of LFP black mass and maintaining an average Li recovery rate of 89.8%.
“Additionally, the MEA reactor can be adapted to a roll-to-roll fashion to produce 0.98 M LiOH and can be extended to other cathode materials,” such as those made with nickel, manganese and cobalt, the researchers point out.
The project was described in a recent issue of the journal Joule.