Upcycling graphite from waste lithium-ion batteries into reduced graphene oxide hybrid composite anodes

• Black mass from end-of-life NCM batteries used for authentic recycling results. • Optimized flotation recovers 94% graphite at 80% grade from spent Li-ion batteries • Graphite recovery and grade are maximized at particle sizes of 25–106 µm and pH of 9. • Recovered graphite converted to rGO and then used in TiNb₂O₇/rGO hybrid anode. • Upcycled anodes deliver ∼138 mAh/g capacity at 0.1C The rapid growth of lithium-ion battery (LIB) usage has intensified the need for efficient recycling strategies, particularly for graphite, the predominant anode material often overlooked in current recovery processes. This study presents a novel approach to upcycling graphite from spent LIBs, focusing on flotation-based separation of graphite from black mass derived from nickel-cobalt-manganese (NCM) battery waste. Spent laptop LIBs were crushed, and the resulting black mass was size-fractionated. Flotation experiments revealed that the optimal particle size of black mass for graphite recovery was 106 – 25 µm, effectively minimizing contamination from metallic foils. Pyrolysis at 500°C efficiently removed organic binders without degrading graphite quality. Systematic flotation tests demonstrated that a slurry pH of 9 yielded the highest separation efficiency. Under these optimized conditions (particle size of 25 – 106 µm, pH 9), graphite recovery exceeded 94%, with a corresponding graphite grade about 80%. The recovered graphite was subsequently converted to graphene oxide and then composited with TiNb₂O₇ to fabricate reduced graphene oxide-based hybrid anodes. Electrochemical evaluation showed that the upcycled composite anodes delivered a reversible capacity of approximately 138 mAh g⁻¹ at a 0.1C rate within a 0.8–3.0 V window. This integrated approach offers a scalable, value-added solution for LIB waste management, supporting circular economy principles and advancing sustainable energy storage technologies.