Selective recovery of graphite from spent lithium-ion battery black mass using froth flotation

Abstract

Rapid electric vehicles and electronics growth have driven a sharp rise in Lithium-ion battery (LIBs) production and are expected to increase spent battery waste. The ‘black mass’ derived from the shredding of spent LIBs is a heterogeneous mixture comprising cathode active materials (lithium cobalt oxide (LCO), nickel-manganese-cobalt oxides (LMCO), lithium iron phosphate (LFP)), anode graphite, current collector foils (aluminum and copper), binders (PVDF), and residual electrolytes and lithium salts. Graphite, a critical anode material in LIBs, has gained prominence as a valuable secondary resource, making its recovery from end-of-life batteries essential for sustainable resource management. Flotation, a proven beneficiation method for natural graphite ores, is now being explored for recovering graphite from secondary sources like spent LIB black mass. This study investigates the selective recovery of graphite from two black mass samples, BM-1 and BM-2, originating from spent LIBs with LFP and LCO chemistries, respectively, through laboratory-scale froth flotation tests using customized collector and frother, namely collector ‘C’ and frother ‘F’, which are synthetic, organic, and proprietary reagents. Collector ‘C’ was varied between 100–500μL, while frother ‘F’ was varied between 10–50μL to evaluate their influence on carbon (graphite) recovery and grade. Comparative flotation tests revealed distinct behaviors between the two samples, attributed to their unique physical and chemical characteristics and carbon content. For BM-1, flotation under optimal conditions (collector ‘C’: 100μL; frother ‘F’: 10μL) achieved a high carbon grade of 87.17% but with modest recovery of 43.44%. Conversely, BM-2, under the same conditions, yielded a lower carbon grade of 66.49% but a much higher recovery of 53.98%. This preliminary investigation demonstrates the feasibility of substantial graphite recovery from black mass; however, further studies involving pretreatment or additional cleaning stages could significantly enhance both recovery and grade.