Bismuth (Bi) is an attractive material as anodes for both sodium-ion batteries (NIBs) and potassium-ion batteries (KIBs), because it has a high theoretical gravimetric capacity (386 mAh g −1 ) and high volumetric capacity (3800 mAh L −1 ). The main challenges associated with Bi anodes are structural degradation and instability of the solid electrolyte interphase (SEI) resulting from the huge volume change during charge/discharge. Here, a multicore-shell structured Bi@N-doped carbon (Bi@N-C) anode is designed that addresses these issues. The nanosized Bi spheres are encapsulated by a conductive porous N-doped carbon shell that not only prevents the volume expansion during charge/discharge but also constructs a stable SEI during cycling. The Bi@N-C exhibits unprecedented rate capability and long cycle life for both NIBs (235 mAh g −1 after 2000 cycles at 10 A g −1 ) and KIBs (152 mAh g −1 at 100 A g −1 ). The kinetic analysis reveals the outstanding electrochemical performance can be attributed to significant pseudocapacitance behavior upon cycling.

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.