New ‘Blue-Green’ Solution For Recycling World’s Batteries


Date: Apr 02, 2019

Rice University researchers literally have a solution to deal with the glut of used lithium-ion batteries left behind by the ever-increasing demand for electric vehicles, cellphones and other electronic devices.

The Rice lab of materials scientist Pulickel Ajayan used an environmentally friendly deep eutectic solvent to extract valuable elements from the metal oxides commonly used as cathodes in lithium-ion batteries. The goal, researchers said, is to curtail the use of harsh processes to recycle batteries and keep them out of landfills.

The solvent, made of commodity products choline chloride and ethylene glycol, extracted more than 90 percent of cobalt from powdered compounds, and a smaller but still significant amount from used batteries.

“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,” Ajayan said.

“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,” he said. “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.”

The results appear in Nature Energy.

“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 also have drawbacks, she said. Pyrometallurgy involves crushing and mixing at extreme temperatures, and the harmful fumes require scrubbing. Hydrometallurgy requires caustic chemicals, while other “green” solvents that extract metal ions often require 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.”

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