Lithium batteries are essential to our lifestyles. From powering wireless earbuds, to providing the energy for EVs, almost all of our consumer goods rely on them for energy storage. That reliance has two drawback – the first is that in these days of throwaway goods, a lot of batteries are consigned to the dump after the product has been replaced. That creates an environmental problem as the used batteries leach toxic chemicals into the environment. The second issue is that we have a shortage of lithium as demand has increased so dramatically. Governments around the world are struggling to secure supplies for their own manufacturing.
The solution to both issues looks to be simple on the surface. Better recycling of the batteries would reclaim the raw materials, securing supply chains and keeping the batteries out of landfill. In practice though, it is proving really difficult to find a commercially viable way to efficiently extract the resources. One of the main problems is that the methods that are currently employed normally involve using a tremendous amount of power to heat the batteries before harvesting the materials. Initially, the battery waste is shredded down to a substance known as black mass, which contains all of the minerals, including lithium, cobalt, nickel, graphite, manganese and aluminum. The black mass then goes through a high temperature process that features strong acids. The results are generally not too great, as lithium is hard to recover and the graphite gets damaged during the process.
Hopefully that scenario could be coming to an end, as researchers from Rice University claim to have found a way to extract almost 95% of metals, including the lithium and graphite, from battery black mass using nothing harsher than citric acid. The new technique involves a microwave-induced plasma treatment with the citric acid and other mild solvents. The microwave-induced plasma breaks down the metal oxide particles as a pretreatment step to make their hydrometallurgical recovery in weaker acids easier. The one-step pre-treatment is designed to work alongside other industrial processes to improve efficiency and reduce impact on the environment, while recovering all critical materials, with minimal chemical and energy usage.
To test the process practically, the team used a custom microwave reactor that was built by one of the researchers. The black mass was then exposed to the plasma for 15 minutes, after which, over 90% of the minerals were recovered in a citric acid bath at room temperature, while lithium was recovered in water. The technique also had another benefit, in that it removed the residues and structural defects that occur on graphite while the battery is in use, making it suitable for reuse in new batteries.
The team has patented the technology and is working on its commercialization. Preliminary analysis suggests the process could outperform current industrial methods.
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