Large size nitrogen-doped graphene-coated graphite for high performance lithium-ion battery anode†
The reversible capacity of commercial graphite anodes for lithium-ion batteries (LIBs) is in the range of 340–360 mA h g−1, which is lower than the theoretical value (372 mA h g−1). Pure graphene anodes with high reversible capacity (>372 mA h g−1) are still not used for industrial production due to their high discharge-voltage plateau, low initial coulombic efficiency, low tap density, etc. Herein, we synthesized new carbon anodes using large-size nitrogen-doped graphene-coated commercial graphite anodes (named LGAs) in which the commercial graphite was wrapped by a number (<5) of nitrogen-doped graphene (LNG) layers. The electrochemical performance of the LGAs was similar to that of commercial graphite, and the high tap density, low discharge potential, and high initial coulombic efficiency of graphite were maintained. However, the LGAs with 1 wt% of LNG were able to achieve a reversible capacity of about 390 mA h g−1, which surpassed the theoretical value of graphite. Meanwhile, the LGAs delivered a reversible capacity of about 164 mA h g−1 at the rate of 5C, which was more than two times higher than that of the pure commercial graphite anodes. The production cost could be kept low only at a very low weight percentage of graphene (1 wt%) in LGA, enabling the large-scale commercial application of graphene in LIBs. Such a simple and scalable method may also be applied to other anode systems, boosting their energy and power densities.