Pulickel Ajayan, a scientist at Rice's lab of materials, used an environmentally friendly deep eutectic solvent to extract valuable elements from the metal oxides commonly used as cathodes in lithium-ion batteries, according to a statement from the university.
A deep eutectic solvent is made by mixing two or more compounds and freezes at temperatures much lower than each of its components. One could literally obtain a liquid from a simple combination of solids.
Researchers said they aimed to curtail the use of harsh processes to recycle batteries and keep them out of landfills.
“Rechargeable battery waste, particularly from lithium-ion batteries, will become an increasingly menacing environmental challenge in the future as the demand for these through their usage in electric vehicles and other gadgets increases dramatically,” said Ajayan.
“It’s important to recover strategic metals like cobalt that are limited in supply and are critical for the performance of these energy-storage devices.
“Something to learn from our present situation with plastics is that it is the right time to have a comprehensive strategy for recycling the growing volume of battery waste.”
“This has been attempted before with acids,” said Rice graduate student and lead author Kimmai Tran. “They’re effective, but they’re corrosive and not eco-friendly. As a whole, recycling lithium-ion batteries is typically expensive and a risk to workers.”
Other processes that have been tried also had drawbacks: pyrometallurgy involves crushing and mixing at very high temperatures, and the harmful fumes require scrubbing. Hydrometallurgy needs caustic chemicals, while other “green” solvents that extract metal ions often need additional agents or high-temperature processes to fully capture them.
“The nice thing about this deep eutectic solvent is that it can dissolve a wide variety of metal oxides,” Tran said. “It’s literally made of a chicken feed additive and a common plastic precursor that, when mixed together at room temperature, form a clear, relatively nontoxic solution that has effective solvating properties.”
A paper about the research has been published in Nature Energy.