▎ 摘　　要

The development of cost- and time-effective methods to synthesize graphene materials is very urgent in order to promote its large-scale application in electrochemical energy storage devices. Herein, graphene materials were synthesized by the electrochemical exfoliation (electrochemical oxidation) of graphite clay rods with different clay:graphite ratios in aqueous solution and in short reaction time (1 h). The dual role of electrochemical oxidation reaction was presented: (1) the electrochemical oxidation reaction facilitates the exfoliation of pencil graphite leads and in-situ forms functional groups on graphene; (2) the electrochemical oxidation reaction enhances the Faradaic reaction in supercapacitor. The in-situ electrochemical oxidation and functionalization methods can transform low purity graphite to high value graphene electrode materials for supercapacitors and lithium ion batteries. The specific capacitances of exfoliated graphene are 20-time larger than that of graphite-clay composites. This work provided a value-added way that can transform the low-purity graphite resources to high performance graphene electrode materials. (C) 2017 Elsevier Ltd. All rights reserved.