Environmental-friendly and effectively regenerate anode material of spent lithium-ion batteries into high-performance P-doped graphite

Recycling graphite from spent lithium-ion batteries has been largely ignored. In the present work, we propose a novel purification process, which modifies the structure of graphite through phosphoric acid leaching-calcination to obtain high-performance phosphorus (P)-doped graphite (LG-temperature) and lithium phosphate products. The content analysis of X-ray photoelectron spectroscopy (XPS), X-ray fluorescence (XRF) and scanning electron microscope focused ion beam (SEM-FIB) indicates that the LG structure is deformed by the doped P atom. The results of In-situ fourier transform infrared spectroscopy (In-situ-FTIR), density functional theory (DFT) calcu-lation and XPS analysis show that the surface of the leached spent graphite contains rich oxygen groups, which react with phosphoric acid at high temperatures and form stable C-O-P and C-P bonds, making it easier to form stable solid electrolyte interface (SEI) layer. The increase of layer spacing is confirmed by X-ray diffraction (XRD), Raman and transmission electron microscope (TEM), which is conducive to the formation of efficient Li+ transport channels. What is more, Li/LG-800 cells possess high reversible specific capacities of 359, 345, 330 and 289 mA h g+1 at 0.2C, 0.5C, 1C and 2C, respectively. After 100 cycles at 0.5C, the specific capacity is as high as 366 mAh g+1, demonstrating the outstanding reversibility and cycle performance. This study proves and high-lights a promising recovery route for exhausted lithium-ion batteries anodes, making complete recycling possible.

Automated summary

This study proposes a new method for recycling graphite from spent lithium-ion batteries through phosphoric acid leaching-calcination. The modified graphite exhibits high-performance phosphorus-doped graphite and lithium phosphate products. This research provides a promising recovery route for exhausted lithium-ion battery anodes, enabling complete recycling.