Ultrafast Sodium Storage through Capacitive Behaviors in Carbon Nanosheets with Enhanced Ion Transport

Abstract Sodium‐ion batteries are regarded as a promising alternative for scalable electricity storage, but the rate capability is still a scientific challenge to be solved, owing to the poor Na + kinetics in electrodes. Herein, nitrogen‐doped carbon nanosheets with rich defects, nanopores and various interlayer spacings are prepared by pre‐carbonized polymer sheets at different temperatures followed by sodium amide treatment. Combination of thin nanosheets, nanopores and large interlayer spacing can boost the rapid Na + diffusion, as proven by the calculation of the diffusion coefficient. Meanwhile, the kinetics analysis demonstrates the capacitive behaviors, which favor fast Na + storage. When applied as an anode, the material exhibits superior rate capability (111.1 mA h g −1 even at 20 A g −1 ), remarkable cycle stability (over 2000 cycles) and ultrahigh initial coulombic efficiency (81.4 %). Furthermore, this work demonstrates a new way to develop attractive high‐rate carbon anode materials for sodium‐ion batteries.