A general strategy towards carbon nanosheets from triblock polymers as high-rate anode materials for lithium and sodium ion batteries

In this work, the triblock copolymer F127 has been used as the carbon precursor to fabricate carbon nanosheets (CNSs) by a sodium chloride surface-assisted bottom-up strategy. The CNSs possess a thickness of about 6 nm and an oxygen content of 15.6 at%. As an anode for lithium-ion batteries, CNSs exhibit reversible capacities of 830 mA h g−1 after 500 cycles at 1 A g−1 and 240 mA h g−1 at 20 A g−1, which is among the best of the reported lithium storage performances of carbon materials. When used as an anode material in sodium-ion batteries, the CNS electrode exhibits a reversible capacity of 367 mA h g−1 at 50 mA g−1 after 60 cycles and still delivers 112 mA h g−1 at 20 A g−1. The high reversible capacity and excellent rate performance would be ascribed to the synergistic effect of the 2D structure, defects, and expanded crystallites. This work extends the sodium chloride template method to prepare thin CNSs by using a suitable carbon precursor and provides some insights into the relationship between the structure of CNSs and the electrochemical performance.