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

Abstract

Separation between two recycled electrode active materials from spent Li-ion batteries by a conventional froth flotation method has been challenging due to similarity in their surface hydrophobicity. In this study, a new coarse flake particle flotation technology has been developed to separate the electrode active materials from Li-ion batteries. The new process separates the recycled electrode flake particles effectively at a size range of 212−850 μm by taking advantage of a significant difference in densities between the anode flake materials and cathode flake materials. At a feed size of 212 μm or less, a fraction of recycled cathode particles is floated in the froth layers resulting in a loss of cathode materials in the sink product. At a feed size of 850 μm or above, a small fraction of anode flakes becomes non-floatable, resulting in a decrease in the grade of cathode materials in the sink product. The mechanism has been investigated by induction time measurements, bubble−flake detachment, contact angle measurements, and force analysis. The anode flakes are more hydrophobic than cathode flakes, which is consistent with the result obtained from induction time measurements. A force analysis reveals that the critical size for electrode flake particles being attached to air bubbles varies with advancing contact angle and density. Maintaining a desirable feed size is essential to achieve an optimum separation performance. In this regard, a flotation column is superior to mechanical flotation cells in minimizing size reduction during the flotation process. Lab-scale column flotation trials showed that a good separation between anode and cathode flake particles has been achieved by column flotation with 98−99% purity of cathode flake materials in the sink product at a recovery rate of 96−99%. The present study demonstrates a new process in separating two electrode flake materials from spent Li-ion batteries.

Engineering Polymer-Based Porous Membrane for Sustainable Lithium-Ion Battery Separators

“…Polyolefin materials such as PE and PP are preferred due to their exceptional mechanical properties, chemical stability, mature manufacturing processes, and low cost; thus, they have been frequently employed as separator components in LIBs research and development [ 28 , 34 ]. While some recent investigations have delved into the utilization of substitute materials (e.g., PVDF) [ 145 , 146 , 147 , 148 ], as the primary polymer in phase inversion methods and cellulose-based composite membranes in LIBs [ 83 , 102 , 149 , 150 , 151 , 152 , 153 ], commercial polyolefin-based LIB separators still predominated the overall LIBs markets, encompassing PE, PP, and UHMWPE [ 7 , 34 ]. Preparation procedures can be segregated into dry and wet methods, based on the varying formation mechanisms of microporous structures [ 30 , 34 ] ( Figure 5 ).…”

“…recent investigations have delved into the utilization of substitute materials (e.g., PVD [145][146][147][148], as the primary polymer in phase inversion methods and cellulose-based com posite membranes in LIBs [83,102,[149][150][151][152][153], commercial polyolefin-based LIB separato still predominated the overall LIBs markets, encompassing PE, PP, and UHMWPE [7,3 Preparation procedures can be segregated into dry and wet methods, based on the varyi formation mechanisms of microporous structures [30,34] (Figure 5). Industrially, the manufacturing focus has been on wet-processed biaxially stretch PE membranes and dry-processed uniaxially stretched PP membranes.…”

The Recycling of Spent Lithium-Ion Batteries: Crucial Flotation for the Separation of Cathode and Anode Materials

“…A new coarse-flake particle flotation technology was studied for the separation of cathode and anode active materials in black mass [ 65 ]. By taking advantage of the significant density difference between anode and cathode flake materials, effective separation and recovery of electrode flake materials could be achieved in the range of 212–850 μm, as shown in Figure 6 c. It was found that the adsorption of flakes and bubbles depended on the combined action of capillary force and gravity.…”

“…2022, MDPI, ( c ) coarse flake particle flotation Reprinted with permission from Ref. [ 65 ]. 2023, ACS.…”