As electric vehicle use rises worldwide, discarded battery packs are rapidly turning into a significant waste source. Lithium is expensive to extract, and most existing recycling techniques consume substantial energy and chemicals, typically yielding lithium carbonate that still requires additional processing to become reusable lithium hydroxide.
Instead of smelting or leaching shredded battery material (“black mass”) with harsh acids, engineers at Rice University have devised a cleaner method: they electrochemically “recharge” the spent cathode material, prompting lithium ions to move into water, where they react with hydroxide to form high-purity lithium hydroxide.
“We posed a simple question: if charging a battery extracts lithium from a cathode, why not use that same process for recycling?” said Sibani Lisa Biswal, chair of Rice’s Department of Chemical and Biomolecular Engineering and the William M. McCardell Professor of Chemical Engineering. “By combining that chemistry with a compact electrochemical reactor, we can recover lithium cleanly and generate the exact salt manufacturers need.”
Electrochemical Recycling of Lithium from Spent Cathodes
In a functioning battery, charging draws lithium ions out of the cathode. Rice’s system applies this mechanism to spent cathodes such as lithium iron phosphate. As the reaction starts, lithium ions pass through a thin cation-exchange membrane into flowing water. At the counter electrode, water splitting produces hydroxide. The lithium and hydroxide then merge in the water stream, forming lithium hydroxide without the use of strong acids or additional reagents.
The work, published recently in Joule, showcases a zero-gap membrane-electrode reactor that runs solely on electricity, water, and battery waste.
In certain operating modes, the method used just 103 kilojoules of energy per kilogram of black mass—roughly ten times less than typical acid-leaching approaches, even before their extra processing steps are considered. The researchers also scaled their reactor to 20 square centimeters, completed a 1,000-hour durability test, and treated 57 grams of industrial black mass.
“Producing high-purity lithium hydroxide directly streamlines the route back into new batteries,” said Haotian Wang, associate professor of chemical and biomolecular engineering and co-corresponding author with Biswal. “It cuts down processing steps, reduces waste, and strengthens the supply chain.”
High-Purity, Energy-Efficient Lithium Recovery Across Multiple Cathodes
The method yielded lithium hydroxide at over 99% purity—suitable for immediate use in battery production. It was also highly energy-efficient, requiring only 103 kilojoules of energy per kilogram of waste in one mode and 536 kilojoules in another. Over 1,000 hours of continuous operation, the system remained stable and scalable, achieving an average lithium recovery rate of nearly 90%.
The technique proved effective with several cathode chemistries, including lithium iron phosphate, lithium manganese oxide, and nickel–manganese–cobalt materials. Notably, the team also demonstrated roll-to-roll processing of whole lithium iron phosphate electrodes straight from aluminum foil, eliminating the need for scraping or other pretreatment.
“The roll-to-roll demonstration shows how this technology could integrate seamlessly into automated battery-disassembly lines,” Wang said. “You feed in the electrode, power the reactor with low-carbon electricity, and collect battery-grade lithium hydroxide on the other end.”
The team’s next steps include scaling the system with larger-area stacks, increasing black-mass loading, and creating more selective, hydrophobic membranes to maintain high efficiency at elevated lithium-hydroxide concentrations. They also view downstream processing—concentrating and crystallizing the lithium hydroxide—as a major opportunity to further reduce energy use and emissions.
“We’ve made lithium extraction cleaner and more straightforward,” Biswal said. “Now the next bottleneck is obvious. Solve the concentration challenge, and sustainability improves even more.”
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