A method for the preparation of graphene from spent graphite of retired lithium-ion batteries

Recycling spent graphite is significant for the sustainable development of the lithium-ion industry. In this study, due to the damaged structure of spent graphite, a modified Hummers' method combined with thermal reduction is proposed to achieve the preparation of graphene and the simultaneous removal of impurities from the spent graphite. In the preparation of graphene oxide, the results show that the optimum mass ratio of spent graphite to oxidizing agent (KMnO4) is 1:3, under which the C/O and ID/IG values of graphene oxide are 1.99 and 1.52, respectively. The residual contents of various metal impurities in graphene oxide are lower than 100 ppm, and the impurities removal efficiency is better than that by acid leaching with the same acid dosage. After thermal reduction, reduced graphene oxide with a disordered few-layer structure is successfully prepared. It shows that spent graphite as a raw material for the preparation of graphene is superior to commercial graphite in terms of cost, and processing one ton of spent graphite yields a profit of $52,651.4. Our research can realize the diversified and efficient utilization of spent graphite and has a broad industrial application prospect.