Green method to recycle spent batteries' lithium

The rise of lithium-ion batteries in electric vehicles and energy storage systems has led to a growing number of retired batteries, posing a significant challenge for sustainable energy development. Chinese scientists have introduced a green recycling strategy that extracts lithium with more than 95 percent efficiency under mild conditions.

The study, recently published in the journal Nature Communications, reveals an innovative "fizzy" method using only carbon dioxide and water. The approach not only recovers lithium but also transforms other metals into high-value catalysts while capturing carbon dioxide.

"Lithium-ion batteries typically degrade after five to eight years, making recycling essential for conserving strategic metals like lithium, cobalt and nickel, while preventing pollution and managing safety risks," said Sun Zhi, a professor at the Institute of Process Engineering at the Chinese Academy of Sciences and the study's corresponding author.

Sun noted that traditional recycling methods often consume large amounts of energy and chemicals, generate pollution, involve complex procedures and yield low-value products. These include pyrometallurgical processes, which require prolonged melting at temperatures exceeding 1,000 C, and hydrometallurgical processes, which involve multiple chemical steps that often produce wastewater and hazardous waste.

To address these issues, the research team developed a method using carbon dioxide as the sole reagent. They grind the cathode material from spent batteries to disrupt its crystalline structure, causing lithium atoms to migrate to the particle surface and form a lithium-rich layer, while other metals, such as nickel and cobalt, remain in the crystal structure. This separation enhances lithium extraction efficiency.

Scientists then soak the material in water and introduce carbon dioxide, a process similar to producing carbonated beverages. Trace hydrogen ions from dissolved carbon dioxide react with the lithium, dissolving it into a lithium bicarbonate solution while leaving other metals unaffected.

By heating the lithium bicarbonate solution, scientists obtain lithium carbonate — a key material for lithium batteries — with a purity exceeding 99.5 weight percent. The solid residue left after lithium extraction is not waste. It has a unique structure that makes it a high-performance catalyst, maintaining stability for more than 200 hours of operation.

"This process, which operates at low chemical consumption, offers an innovative green solution for recycling spent lithium-ion batteries," Sun said, emphasizing its potential to support China's dual carbon goals of peaking carbon emissions before 2030 and achieving carbon neutrality before 2060.

"In the future, we plan to explore the direct use of industrial flue gas containing low concentrations of carbon dioxide in this process, further enhancing its environmental and economic benefits," he added.

limenghan@chinadaily.com.cn