Direct exfoliation of the anode graphite of used Li-ion batteries into few-layer graphene sheets: a green and high yield route to high-quality graphene preparation

Recycling anode graphite remains a significant barrier to the recovery of used Li-ion batteries. In this study, we show that anode graphite in used lithium-ion batteries is a cheap and ideal candidate for the high yield production of high-quality graphene. Attributed to the reduced interlayer force after repeated charge-discharge cycles, the sonication assisted exfoliation efficiency of the used anode graphite can be 3 to 11 times that of natural graphite, with a highest mass yield of the dispersed graphene sheets of similar to 40 wt%. Importantly, the layer numbers of most of the exfoliated graphene sheets are 1-4, and their lateral sizes are over 1 mm. Their conductivity after annealing at moderate temperature (500 degrees C) is up to 9100 S m(-1), and their potential application in conductive ink was also demonstrated.