Sustainable and Direct Upcycling of Waste Graphite Anodes via Deep Eutectic Solvents.

Lithium-ion batteries (LIBs) have flourished in power and energy storage, followed by the waste batteries that are pouring into the market. For waste graphite anode, how to deal with high efficiency, high economic efficiency, and low environmental pollution has become a huge challenge. In the work, a deep eutectic solvent (DES), with a low melting point, low cost, and natural environmental protection, is applied as a green reagent to realize the sustainable and direct upcycling of waste graphite. Substances in DES existing in the form of ions and charged P-containing groups are more likely to attack defect-rich graphite and realize in situ phosphorus doping, and doped phosphorus participates in the construction of LiPO-rich solid electrolyte interphase (SEI). Due to the reconstruction of phosphate-rich interfacial film, the capacity of regenerated graphite maintains as high as 365 mAh g at 0.5C with a capacity retention rate of 95.5%, which is much higher than that of waste graphite and even commercial graphite. In addition, the low melting point of DES makes the regeneration temperature significantly lower, so that the strategy reduces the CO emissions of energy consumption. More importantly, the environment and economy have been optimized, which is conducive to its large-scale promotion in industry.