Efficient separation and recovery of lithium and manganese from spent lithium-ion batteries powder leaching solution

Abstract

Spent lithium-ion batteries recycling have become the key to the sustainable development of new energy vehicle industry due to its potential environmental risks and scarcity of critical metals. In this paper, rapid separation and efficient recovery of lithium and manganese were achieved through “manganese precipitation - acid leaching of manganese - impurities removal by sulfide precipitation” for the leaching solution of spent lithium-ion batteries powder. Based on the thermodynamic simulation of element precipitation behavior in Li+-Mn2+-Ni2+-Co2+-F−-SO42−-Ca(OH)2-H2O system, Ca(OH)2 was used to adjust the system pH of Li-Mn solution to 10, the elements such as Mn, Ni, Co, Ca and F were precipitated simultaneously as Mn(OH)2(s), Ni(OH)2(s), Co(OH)2(s), CaSO4(s) and CaF2(s). Whereas the loss rate of lithium was less than 0.2 %. Battery-grade lithium carbonate (Li2CO3 99.80 %) was prepared from the lithium purification solution with the carbonation method. Using 30 % H2O2 as reductant, the leaching rate of Mn from the manganese precipitate residue was 99.77 %. In order to realize the deep purification of manganic acid leaching solution, solid manganese sulfide was selected as the precipitant, and impurities such as Co, Ni, Ca and F were selectively precipitated as CoS(s), NiS(s) and CaF2(s), respectively, at pH = 5.0. Subsequently, battery-grade manganese sulfate was successfully prepared from the pure MnSO4 solution by evaporation - crystallization. In this study, the introduction of cationic impurities such as Na+ and NH4+ was avoided during Li-Mn separation and acid-leachate purification through the selection of suitable neutralizer and sulfide precipitant. As a result, the process flow was greatly simplified, and the direct yields of lithium and manganese were effectively improved.