Applications of lithium-ion batteries (LIBs) are growing. Therefore, their efficient and green recycling is of great interest. Zheng Chen, University of California San Diego, La Jolla, USA, and colleagues have developed a non-destructive method to regenerate cathode materials by hydrothermal treatment of cycled electrode particles followed by short annealing: Degraded cathode particles from a used battery were pressurized in a hot alkaline solution with lithium salt, then annealed at 800 °C, cooled, and used in new lithium-ion batteries.

According to the team, storage capacity, charging time, and battery lifetime were restored to their original levels. The regenerated LiCoO₂ particles show much better rate capability than particles regenerated through the solid-state synthesis approach. The process uses 5.9 MJ to restore 1 kg of the cathode material. This is less than half the amount used by other cathode recycling techniques. Conventional chemical leaching or solid-state synthesis require either complicated steps of leaching, precipitation, and waste treatment or rely on the chemical analysis of the Li/Co ratio from cell to cell.

According to the researchers, their environmentally friendly, simple approach can be widely used to recycle and regenerate LiCoO₂ cathodes on a large scale, and it can be potentially applied to other types of cathode materials in LIBs and mixed cathode chemistry.

• Effective regeneration of LiCoO₂ from spent lithium-ion batteries: a direct approach towards high-performance active particles,
  Yang Shi, Gen Chen, Zheng Chen,
  Green Chem. 2018.
  https://doi.org/10.1039/C7GC02831H