SPENT BATTERY FLOWS, CHARACTERIZATION AND RECYCLING PROCESSES

Spent batteries are an important waste flow regarding the recovery of the contained metals motivated by economic, environmental and strategic reasons. The portable battery market is dominated by primary Zn-Mn cells, but the market of secondary batteries are continuously growing, with particular relevance for Li-ion batteries, used in practically all electronic devices. The batteries are metal concentrates, having metal grades such as 20%–30% of Zn, Mn, Co, Ni, depending on the battery system. These metals are specifically concentrated in the electrodes, which are the most important component of a battery. The most usual chemical forms of these metals in the electrodes are oxides or hydrated oxides, but other solid phases can be found such as metal alloys. The recycling of batteries can be done by pyrometallurgical and hydrometallurgical processes. The first one usually involves the distillation of some more volatile metals, such as Zn in Zn-Mn cells and Cd in Ni-Cd cells. For Ni-MH and Li-ion batteries, some pyrometallurgical approaches involve the melting and recovery of Ni or Co, but with losses of other metals (like lithium and rare earths). The hydrometallurgical alternative allows higher metal recovery rates, as practised industrially for Zn-Mn and Li-ion batteries. Many studies on alternative processes for recycling Li-ion batteries have been intensively carried out due to the special interest on these batteries nowadays and in the future.