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.

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