Efficient process for recovery of waste LiMn2O4 cathode material precipitation thermodynamic analysis and separation experiments

Abstract

An efficient process is proposed for recovery of waste LiMn₂O₄ cathode material, which is one of the most commonly used cathode materials in LIBs. This report constitutes the precipitation thermodynamic analysis and separation experiments based on the water-leaching solutions during the processes of low-temperature calcination with (NH₄)₂SO₄ and water-leaching. Precipitation thermodynamic analysis is undertaken to investigate the effects of initial concentration of the target solution, [N]_T1, excess precipitant, and addition of (NH₄)₂SO₄ on the manganese precipitation in the Mn²⁺-Li⁺-SO₄^2--NH₃-NH₄⁺-CO₃^2--H₂O system. Moreover, the effects of initial concentration of the target solution, [N]_T2, and excess precipitant on the lithium precipitation in the Li⁺-SO₄^2--NH₃-NH₄⁺-CO₃^2--H₂O system are investigated. All these factors clearly influence the manganese and lithium precipitation, particularly the [N]_T and the presence of excess precipitant in the system. The precipitation experimental results demonstrate that the optimal conditions are: a precipitation temperature of 35 °C; an excess coefficient of the precipitant of 2.4; the use of NHC-3 to precipitate the ML-3 solution; a maximum precipitation percentage of manganese of 99.96%; and an absence of Li₂CO₃ precipitation. The double-sulfate salts (Li(NH₄)SO₄ & (NH₄)₂SO₄) evaporated and crystallised from the Li⁺/NH₄⁺ solution are mixed with the waste LiMn₂O₄ cathode material for calcination and water leaching, for which the efficiencies of Li and Mn are 100% and 96.89%, respectively. The double-sulfate salts are calcined at 550 °C for 45 min to obtain the Li₂SO₄ product. Finally, the complete recovery and separation of Mn and Li in the waste LiMn₂O₄ cathode material are achieved.

Keywords: Complete recovery and separation of Mn and Li; Precipitation thermodynamic analysis; Separation experiments; Waste LiMn(2)O(4) cathode material.