Li+Extraction from Spinel-Type LiMn2O4in Different Eluents and Li+Insertion in the Aqueous Phase

In order to afford a possible way to avoid manganese dissolution during Li+ extraction/insertion of spinel-type LiMn2O4, the elution properties of HCl, (NH4)2S2O8, and Na2S2O8 were studied and the adsorption performance of Li+-extracted samples was characterized in Li+-containing solution. The results showed that Li+ was extracted by two different pathways: with manganese loss and without manganese loss. In the Li+ extraction process with manganese loss, ionic sieve was obtained after extracting Li+ from its precursor LiMn2O4, with accompanying partial transformation of Mn3+ to Mn4+ and Mn2+ by disproportionation reaction. This change caused the destruction of the framework and weight loss of ionic sieve due to the dissolution of Mn2+ in the solution. In the Li+ extraction process without manganese loss, Li+ was extracted with the reaction that part of Mn3+ was oxidized to Mn4+ by S2O82-. The Li+-extracted sample contained a small number of H+ which should exchange Li+ during this type of elution. The two Li+ extraction pathways also indicated that Li+ could not be completely eluted from the ionic sieve precursor. The uptake of Li+ on the ionic sieve was incomplete.