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

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.