A low-temperature solid-to-solid reaction for lithium-ion battery recycling and the utilization of defect-enriched Co3O4 from spent LiCoO2 batteries for efficient oxygen evolution reaction

An efficient, eco-friendly and cost-effective strategy for the recovery of precious metals from spent lithium-ion batteries (LIBs) is of great significance for the sustainable natural resource utilization and environmental protection. Herein, a low-temperature solid-to-solid reaction combined water leaching technology is proposed for the preferential extraction of Li from spent LiCoO2 batteries. In the solid-to-solid reaction, crystal water released from the oxalic acid dihydrate acts as a lubricant and initiates the reduction reaction to convert the spent LiCoO2 into water-soluble Li salts (LiHC2O4 or Li2C2O4) and water-insoluble CoC2O4. After water leaching, the collected Li-rich solution and the Co-rich residue are separately transformed into Li2CO3 and Co3O4. Additionally, a defect-enriched Co3O4 is prepared by water quenching process, exhibiting excellent performances towards oxygen evolution reaction. This work not only achieves a facile, low-cost and energy-saving strategy for recycling spent LIBs, but also proposes a vacancy-defected engineering route for electrocatalyst design in energy-related applications.