Sodium/Potassium‐Ion Batteries: Boosting the Rate Capability and Cycle Life by Combining Morphology, Defect and Structure Engineering

Abstract Carbon‐based materials have been considered as the most promising anode materials for both sodium‐ion batteries (SIBs) and potassium‐ion batteries (PIBs), owing to their good chemical stability, high electrical conductivity, and environmental benignity. However, due to the large sizes of sodium and potassium ions, it is a great challenge to realize a carbon anode with high reversible capacity, long cycle life, and high rate capability. Herein, by rational design, N‐doped 3D mesoporous carbon nanosheets (N‐CNS) are successfully synthesized, which can realize unprecedented electrochemical performance for both SIBs and PIBs. The N‐CNS possess an ultrathin nanosheet structure with hierarchical pores, ultrahigh level of pyridinic N/pyrrolic N, and an expanded interlayer distance. The beneficial features that can enhance the Na‐/K‐ion intercalation/deintercalation kinetic process, shorten the diffusion length for both ions and electrons, and accommodate the volume change are demonstrated. Hence, the N‐CNS‐based electrode delivers a high capacity of 239 mAh g −1 at 5 A g −1 after 10 000 cycles for SIBs and 321 mAh g −1 at 5 A g −1 after 5000 cycles for PIBs. First‐principles calculation shows that the ultrahigh doping level of pyridinic N/pyrrolic N contributes to the enhanced sodium and potassium storage performance by modulating the charge density distribution on the carbon surface.