(ii) Hydrometallurgical method: Hydrometallurgical processes are focused on dissolving valuable metals in order to separate, purify and finally obtain precursors of new active materials. The active materials are concentrated in the black mass through the discharge, crushing and fractionation of spent batteries, followed by lixiviation (mainly inorganic or organic acids) and purification steps (selective precipitation ion-exchange and/or solvent extraction, etc.), which enables high purity of the products. However, this approach requires sorting and mechanical pre-treatments which are dangerous. In general, this route is more complex than pyrometallurgical one and overall costs are higher .