Recovery of spent LiCoO2 cathode material: Thermodynamic analysis and experiments for precipitation and separation of elements

A process for recycling spent LiCoO2 cathode material doped with Mn from spent LiCoO2 lithium-ion batteries is proposed in this paper. Based on the leachate obtained during calcination and water leaching, this report comprises precipitation thermodynamics analysis and separation experiments results. The results of precipitation thermodynamic analysis demonstrate that NH4HCO3 cannot achieve separation of Mn and Co in the waterleaching solution system, while using (NH4)2S2O8 can induce preferential oxidative precipitation of the Mn in the system at pH < 2 and thus achieve the separation of Mn. Moreover, some factors clearly influence Co2+ precipitation, particularly total NH4+/NH3 concentrations and the excess precipitant in the system. The results of the experiments demonstrate that the optimal conditions are a reaction temperature of 90 <degrees>C, (NH4)2S2O8 excess coefficient of 1.5, and LC-2 leachate, which yield a Mn precipitation percentage of 99.95% and only 0.85 mg/L Mn is left in the solution. After the separation of Mn from LC-2 leachate, a precipitation temperature of 45 degrees C and NH4HCO3 precipitant excess coefficient of 2.5 yield a Co precipitation percentage of 98.03% and the absence of Li2CO3 precipitation. Then, a Li-rich solution containing Li+/NH4+ is obtained after circulating enrichment and thorough Co removal. Meanwhile, a sulfate compound is produced by evaporation and crystallisation, which is then calcined at 550 degrees C for 45 min to obtain the Li2SO4 product.