The increasing prevalence of electric vehicles and renewable energy storage has led to a sharp rise in demand for lithium-ion batteries. This trend underscores the urgent need for sustainable management of spent batteries. While most recycling methods prioritize the recovery of metals such as nickel, manganese, and cobalt from the cathode, the graphite-rich anode is frequently neglected despite constituting a significant portion of battery waste. Efficient recovery of graphite is essential for resource optimization and the advancement of a circular battery economy.
This study investigates an integrated recycling approach for recovering a carbon- rich graphite concentrate from spent nickel-manganese-cobalt lithium-ion battery black mass. The study focuses on the removal of polyvinylidene fluoride (PVDF), which masks the surface properties of electrode particles and hinders selective separation. Triethyl phosphate (TEP) and dimethyl sulfoxide (DMSO) were evaluated as lower-hazard solvent alternatives, while dimethylformamide (DMF) was used as a conventional benchmark. Because the tested solvent treatments did not achieve sufficiently complete or selective removal of PVDF, thermal pretreatment was subsequently applied before flotation.
The effects of thermal pretreatment on the surface characteristics of the composite black mass were assessed using contact-angle and zeta-potential measurements. The thermally treated sample exhibited moderate hydrophobicity, indicating that the removal of FTIR-detectable binder residues created surface conditions conducive to subsequent flotation. However, because these measurements were conducted on a heterogeneous black mass sample, they were interpreted as composite surface responses rather than separate measurements of graphite and cathode phases.
Froth flotation experiments were conducted to evaluate the individual and combined effects of kerosene, pine oil, and sodium metasilicate. Among the tested conditions, kerosene provided the highest single-stage carbon grade, and a multi-stage rougher-cleaner circuit increased the carbon content of the concentrate to approximately 94 wt.%. Subsequent purification using sulfuric acid and hydrogen peroxide increased the final total carbon content to approximately 96 wt.%.
The recovered carbon-rich material was evaluated by fabricating coin cells and conducting galvanostatic cycling tests. The material demonstrated some lithium-ion storage capability; however, it exhibited rapid capacity loss within the first five cycles. Its performance was significantly lower than that of commercial graphite. To render the material suitable for battery reuse, further purification, structural enhancements, improved electrode formulation, and extended testing are required.
In summary, this study demonstrates the technical feasibility of integrating thermal pretreatment, multi-stage flotation, and chemical purification to recover a high-carbon concentrate from spent NMC lithium-ion battery black mass. The green-solvent treatments investigated were not sufficiently effective under the tested conditions; however, their evaluation clarified the limitations of solvent-based PVDF removal. The proposed process constitutes a preliminary step toward more resource-efficient battery recycling, although further process optimization and validation are necessary prior to industrial or closed-loop implementation.

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