Preparation of carbon nanosheets from petroleum asphalt via recyclable molten-salt method for superior lithium and sodium storage

Carbon nanosheets were successfully prepared from easily available and low-cost petroleum asphalt via a facile and recyclable molten-salt method. The as-made carbon nanosheets exhibit excellent performance on energy storage both for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs): as the anode of LIBs, they provide a high reversible specific capacity (729 mAh g(-1) at 100 mA g(-1)), excellent cyclability (600 mAh g(-1) at 1 A g(-1) after 500 cycles), and improved rate performance (280 mAh g(-1) at 5 A g(-1)). For SIBs, they also display a reversible capacity of 300 mAh g(-1) at 50 mA g(-1), remarkable rate capability (90 mAh g-1 at 5 A g(-1)) and retain as high as 95 mAh g(-1) after 10000 cycles at 2 A g(-1). The superior electrochemical performance of carbon nanosheets could be attributed to their peculiar structural characteristics that integrate a variety of advantages: fast electronic and ionic conductivity, easy penetration of the electrolyte, shortened path for Li+/Na+ migration and structural stability. This approach paves the way for industrial scale-up due to its eco-friendliness, simplicity and versatility. (C) 2017 Elsevier Ltd. All rights reserved.