A green process for recycling and synthesis of cathode materials LiMn2O4 from spent lithium-ion batteries using citric acid.

Abstract

In view of the reducing reagent consumption and secondary pollution caused by recycling spent lithium-ion batteries (LIBs), a relatively green process has been proposed, because the complex process to separate metals and the use of a large number of environmentally unfriendly chemical reagents are not involved. This process combines acid leaching with the resynthesis of the cathode material to recycle LiMn2O4 (LMO) from spent LIBs. The leaching efficiencies of Li and Mn exceeded 94% under the conditions of 1.0 M citric acid concentration, solid–liquid ratio of 60 g L−1, and 60 min leaching time. After the leaching process, spinel LMO was successfully resynthesized by the sol–gel process using leachate. The sample calcined at 700 °C has the best electrochemical performances, and the initial discharge capacity at a 2C rate and capacity retention after 100 cycles were 87.85 mA h g−1 and 93.63%, respectively. The resynthesized cathode material possessed excellent cycling performance, which may result from Al doping. Furthermore, the mechanism of overall reaction and the formation process of complex Mn(C6H6O7)·H2O in the leaching process were explored. This study indicates that citric acid is an effective reagent for recycling cathode materials and the process is feasible.