Researchers at the University of California San Diego say they have improved the safety of a recycling process that regenerates degraded cathodes from spent lithium-ion batteries.
The research is part of a larger effort under the US ReCell Center initiative to promote ithium-ion battery recycling.
Project leader Zheng Chen (pictured), a professor of nanoengineering affiliated with the Sustainable Power and Energy Center at UC San Diego, said: “Due to the rapid growth of electric vehicle markets, the worldwide manufacturing capacity of lithium-ion batteries is expected to reach hundreds of gigawatt hours per year in the next five years.”
“This work presents a solution to reclaim the values of end-of-life lithium-ion batteries after five to 10 years of operation.”
Chen said his team previously developed a direct recycling approach to recycle and regenerate degraded cathodes that replenished lithium ions lost by cathodes over extended use and “restored their atomic structures to their original states”.
However, that process involved pressurising a hot lithium salt solution of cathode particles to around 10 atmospheres. This pressurising step raised costs and required extra safety precautions and special equipment.
Now the team has developed “a milder process” to do the same job at ambient pressure (1 atmosphere). The key was using eutectic lithium salts— a mixture of two or more salts that melts at temperatures much lower than either of its components. This combination of solid lithium salts produces a solvent-free liquid that researchers can use to dissolve degraded cathode materials and restore lithium ions without adding any extra pressure in the reactors.
The mixture is heat treated in two steps— first heated to 300C, then it goes through a short annealing process in which it is heated to 850C for several hours and cooled naturally.
Details of the research are online.
