▎ 摘　　要

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.