Graphene‐Encapsulated Nitrogen‐doped Carbon@Bi Enables Rapid, Ultrahigh and Durable Sodium Storage

Abstract Bismuth (Bi) has promising applications as anode in sodium‐ion batteries (SIBs) due to its suitable alloy voltage, unique lattice structure and high volumetric specific capacity. However, the severe structural degradation and poor cycling performance of Bi‐anode during cycling limits its practical application. Here, we designed and synthesized graphene‐encapsulated nitrogen‐doped carbon@bismuth (N−C@Bi/G) composites as anode materials for SIBs by a two‐step hydrothermal and thermal treatment method to solve the above problems. The N−C@Bi/G composite anode material exhibits excellent sodium storage performance, high capacity (280 mAh g⁻¹ at 0.1 A g⁻¹ and an initial coulombic efficiency of 78.87 %) and long‐term cycling stability (260 mAh g⁻¹ after 1000 cycles at 2 A g⁻¹). Electrochemical analysis and DFT calculations show that the fast reaction kinetics of N−C@Bi/G is directly related to the introduction of nitrogen‐doped carbon enriching the pore structure and increasing the active sites. Meanwhile, through the aid of in‐situ X‐ray diffraction (XRD), the reaction mechanism and interphase evolution of N−C@Bi/G composite are revealed, which provides an important theoretical basis for the application of SIBs.