Efficient regeneration of anode graphite from spent lithium-ion batteries using a deep eutectic solvent method

Herein, a rational-designed green deep eutectic solvent method is employed for efficient regeneration of the anode graphite from the spent batteries. The solid electrolyte interphase layer and metal ions coats on the graphite surface can be efficiently removed through the proton-donor effect from the Lewis acid-assisted deep eutectic solvent, leading to well-preserved bulk graphite, greatly reduced electrochemical impedance and polarization. The regenerated graphite exhibits an initial specific capacity of 344.5 mAh g −1 at a current density of 0.2C, with a capacity retention rate of 98.9 % after 160 cycles. The specific capacity is close to 96.7 % of the commercial graphite (356.5 mAh g −1 ) at that condition. Further, the regenerated graphite also possesses a high specific capacity of 218.0 mAh g −1 at 1C, approximately 3.3 times the improvement of the spent graphite (66.5 mAh g −1 ). Moreover, an economic analysis of the regenerated graphite suggests that the utilization of the green solvent to regenerate the anode graphite is a cost-effective method to reduce energy consumption by 69.0 % compared to high-temperature acid leaching recycling. This work provides a promising green approach to regenerate and reutilize the anode graphite materials from industrial spent lithium-ion batteries. A green and cost-effective route is explored for the graphite recovery from the spent batteries by the proton-donor effect in Lewis acid-assisted DES solution. • The spent negative graphite is efficiently regenerated by a green deep eutectic solvent strategy. • The weak Lewis acid provides protons to remove the SEI layer on the graphite surface. • The specific capacity of regenerated graphite achieves to 96.7% of the commercial graphite. • The deep eutectic solvent can be recovered and reused in the next separation cycles.