Researchers from Rice University developed a new solution to deal with excess of used lithium-ion batteries, according to a report published on April 1, 2019.
Researchers extracted valuable elements from the metal oxides that are commonly used as cathodes in lithium-ion batteries by using a deep eutectic solvent, which is environment-friendly. The main aim was to reduce the use of harsh processes to recycle batteries and keep them out of landfills.
Over 90 percent of cobalt could be extracted from powdered compounds by using the solvent, which is made of commodity products choline chloride and ethylene glycol. Also, a smaller but still significant amount was extracted from used batteries. The process that use acid is not preferred, as it has major drawbacks like many other processes.
A mixture of two or more compounds that freezes at temperatures much lower than each of its precursors is called as deep eutectic solvent. In that way, she said, one can literally obtain a liquid from a simple combination of solids. When Kimmai Tran, lead author, joined, researchers had already started testing a eutectic solution as an electrolyte in next-generation high-temperature supercapacitors.
Trans tested deep eutectic solvents on metal oxides at different temperatures and time scales. When the tests were conducted with lithium cobalt oxide powder, a wide spectrum of blue-green colors that indicated the presence of cobalt dissolved within were yielded by the clear solvent. Around 90 percent of lithium ions were extracted by the solvent at 180 degrees Celsius. Moreover, up to 99 percent of cobalt ions were extracted from the powder when certain conditions were satisfied.
Small prototype batteries were built by researchers, which were then cycled 300 times before exposing the electrodes to the same conditions. They found that the solvent easily dissolved the cobalt and lithium while separating the metal oxides from the other compounds present in the electrode.