A Facile Strategy for Reclaiming Discarded Graphite and Harnessing the Rate Capabilities of Graphite Anodes

Abstract

Graphite negative electrodes are unbeaten hitherto in lithium-ion batteries due to their unique chemical and physical properties. Thus, the increasing scarcity of graphite resources makes smart recycling or repurposing of discarded graphite particularly imperative. Herein a facile and efficient hydrometallurgical process is reported to effectively regenerate aged (39.5%, 75% state-of-health, SOH) scrapped graphite (SG) from end-of-life lithium-ion batteries. Ultimately, the first cycle reversible capacity of SG1 (SOH  39.5%) improved from 266 mAh/g to 337 mAh/g while 330 mAh/g (98%) remain after 100 cycles at 0.5 C. The reversible capacity for the first cycle of SG2 (SOH 75%) boosted from 335 mAh/g to 366 mAh/g with the capacity retention of 99.3% after 100 cycles at 0.5 C, which is comparable with the benchmark commercial graphite. RG1 and RG2 exhibit excellent output characteristics even increasing the rate up to 4 C. This is the best rate level reported in the literature to date. Finally, the diffusion coefficient of Li ions during deintercalation and intercalation in RGs are values 2 orders-of-magnitude higher than that of the spent counterparts. Taking advantage of the synergistic effect of acid leaching and heat treatment, this strategy provides a simple and up-scalable method to recycle graphitic anodes.

Keywords: State of health, Discarded graphite, Recycling, Rate-capability, Lithium-ion diffusion coefficient