Lithium-Ion Battery Recycling─Influence of Recycling Processes on Component Liberation and Flotation Separation Efficiency

Abstract

Recycling is a potential solution to narrow the gap between the supply and demand of raw materials for lithium-ion batteries (LIBs). However, the efficient separation of the active components and their recovery from battery waste remains a challenge. This paper evaluates the influence of three potential routes for the liberation of LIB components (namely mechanical, thermomechanical, and electrohydraulic fragmentation) on the recovery of lithium metal oxides (LMOs) and spheroidized graphite particles using froth flotation. The products of the three liberation routes were characterized using SEM-based automated image analysis. It was found that the mechanical process enabled the delamination of active materials from the foils, which remained intact at coarser sizes along with the casing and separator. However, binder preservation hinders active material liberation, as indicated by their aggregation. The electrohydraulic fragmentation route resulted in liberated active materials with a minor impact on morphology. The coarse fractions thus produced consist of the electrode foils, casing, and separator. Notwithstanding, it has the disadvantage of forming heterogeneous agglomerates containing liberated active particles. This was attributed to the dissolution of the anode binder and its rehardening after drying, capturing previously liberated particles. Finally, the thermomechanical process showed a preferential liberation of individual anode active particles and thus was considered the preferred upstream route for flotation. However, the thermal treatment oxidized Al foils, rendering them brittle and resulting in their distribution in all size fractions. Among the three, the thermomechanical black mass showed the highest flotation selectivity due to the removal of the binder, resulting in a product recovery of 94.4% graphite in the overflow and 89.4% LMOs in the underflow product.

Sorting Lithium-Ion Battery Electrode Materials Using Dielectrophoresis

“…As about one-half of the weight of LIBs consists of the active material of anodes and cathodes, their recycling is desirable . Cathode active materials typically are lithium metal oxides (e.g., LiCoO 2 , LiFePO 4 , or LiNi 1/3 Mn 1/3 Co 1/3 O 2 ), whereas graphite is common for anodes. , Anodes and cathodes consist, among carbon black as a conductive additive and a polymer binder, of a current collector (Cu or Al foil) to which the active material adheres. − The current collector and the active material can be separated by both chemical and mechanical approaches, such as crushing and sieving. ,− Typically, one product of these processes is the so-called black mass, a mixture of anode and cathode active materials . Current recycling techniques for black mass are, for example, pyro- or hydrometallurgical and focus on the recovery of the cathode active material because of its higher value than that of graphite.…”

“…Current recycling techniques for black mass are, for example, pyro- or hydrometallurgical and focus on the recovery of the cathode active material because of its higher value than that of graphite. Graphite might be lost or burned as an energy source within the recycling process. ,,− Yet processes exist where graphite can be recovered. In hydrometallurgical approaches, lithium metal oxides are dissolved in acid during a leaching step and recovered in subsequent unit operations.…”

“…One approach that is well established for particulate systems and capable of handling large amounts of product is flotation, which was also applied to separate black mass. This works because anode and cathode materials show different wettability. ,,− However, according to Neumann et al, the process needs to be optimized further, as the achievable recovery rates are currently too low. Other direct approaches that utilize, for example, eutectic salts or ionic liquids can be found in two recent reviews , that elaborate these techniques in more detail than the scope of this study.…”

Improved Separation between Recycled Anode and Cathode Materials from Li-Ion Batteries Using Coarse Flake Particle Flotation

“…36 As a result, flotation separation efficiency for spent LIBs and manufacturing scraps may vary. 29,37,38 It has been previously demonstrated that the separation of pristine anode and cathode active materials can be easily accomplished by the froth flotation method. 34 Both the PVDF binders and carbon additive affect and complicate the flotation separation performance between the anode and cathode materials.…”

“…These factors include (a) surface degradation on active materials after battery cycling, (b) the presence of hydrophobic polyvinylidene fluoride (PVDF) binders in cathode composite materials, and (c) the presence of various binders in anode composite materials . As a result, flotation separation efficiency for spent LIBs and manufacturing scraps may vary. ,, It has been previously demonstrated that the separation of pristine anode and cathode active materials can be easily accomplished by the froth flotation method . Both the PVDF binders and carbon additive affect and complicate the flotation separation performance between the anode and cathode materials. , Furthermore, the presence of electrolytes and binders causes entrainment, limiting the separation efficiency of the process …”