High-performance expanded graphite regenerated from spent lithium-ion batteries by integrated oxidation and purification method.

Currently, the recycling of spent lithium-ion batteries (LIBs) has mainly been focused on the extraction of precious metals, such as lithium, cobalt and nickel from cathodes, while the waste graphite anode has been overlooked due to its low-cost production and abundant resources reserve. However, there are enormous potential value and pollution risk in the view of graphite recycling. Thus, we propose an original method to prepare expanded graphite (EG) as new anode material generated from waste graphite in LIBs which integrates the oxidation and purification in one-step. By regulating the oxidizability of potassium hypermanganate in the sulfur-phosphorus mixed acid system, the expansion of graphite and removal of impurities are realized simultaneously and thoroughly. As anticipated, the shortening of preparation process and purification procedure can also reduce the generation of polluting substances and production cost. It displays excellent electrochemical performance (reversible capacity of 435.8 mAh·g at 0.1C and long-term cycling property of 370 mAh·g at 1C after 1000 cycles), which is even higher than that of pristine commercial graphite. This delicate strategy of high-performance expanded graphite recycling achieves the integration of purification and value-added processes, providing the instructive guide to regenerate industrial-grade anode materials for the increasing LIBs demand in the future.