Characteristics of Spent Lithium Ion Batteries and Their Recycling Potential Using Flotation Separation: A Review

At the end of their efficient functionality in energy production/storage applications, spent lithium-ion batteries need to be recycled. Recycling remains the most preferred economic option with benefits such as prevention/reduction of environmental issues due to landfilling and more efficient use of natural resources. In this paper, characteristics of lithium-ion battery components before and after being spent are presented, together with highlights of various extractive options suitable for recycling. The main emphasis of this review is on the direct recycling approach, which employs the physical separation of anode and cathode materials. Since flotation is the most common processing method successfully applied to the physical separation of minerals in the mining industry, researchers have given a lot of attention to this area. The success of recycling by flotation is mainly dependent on wettability differences between the anode (hydrophobic) and cathode (hydrophilic) components. However, such components are subjected to surface modifications due to the intimate organic coating introduced in battery production. As such, the hydrophobic entities of the solid electrolyte in battery assembly, which are so essential for the electrochemical functionality of the battery during its life cycle, present main challenges on the selectivity of flotation as a recycling option. Thus, the restoration of the original hydrophobicity/hydrophilicity level of each electrode has been the main focus area for many investigations. This paper also provides an up-to-date review of proposed pretreatment options.