Graphite recovery and synthesis of graphene oxide from end-of-life Li-ion batteries: Impact of thermal, mechanical, and mechanochemical pretreatments

This study investigates how common pretreatments for recovering black mass from end-of-life (EoL) electric vehicle (EV) lithium-ion batteries (LIBs) influence graphene oxide (GO) synthesis. Black mass was obtained through (i) industrial-scale carbothermal reduction of whole EV battery packs, (ii) industrial-scale mechanical processing, and (iii) lab-scale mechanochemical treatment via reactive ball milling. Characterizations assessed the impact of these pretreatments, along with conventional acid leaching, on graphite properties such as interlayer spacing, oxidation degree, and defectivity—key factors for potential anode reuse. The mechanochemically treated sample achieved an outstanding GO yield of 92 %, whereas other black masses reached up to 30 %. GO yields were further analysed using the Hummers’ method after acid leaching for metal removal. This approach enhanced yields, reaching 96 % for the mechanochemically treated sample and up to 46 % for the others. The improvements were attributed to reduced reagent consumption and the partial exfoliation and oxidation of graphite during leaching. Additionally, lithium intercalation/deintercalation during battery cycling increased GO yield compared to commercial pristine graphite. These findings highlight mechanochemical pretreatment as a promising strategy to integrate high-yield GO production into LIB recycling workflows. The black masses recovered from three different pretreatments were used as a graphite source for the synthesis of GO. By applying the Hummers' method to the mechanochemically treated black mass, a GO yield of 92 % is achieved. For the other black masses, the GO yield can be increased by applying conventional acid leaching generally performed during hydrometallurgical recycling.