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 [email protected] (N−[email protected]/G) composites as anode materials for SIBs by a two-step hydrothermal and thermal treatment method to solve the above problems. The N−[email protected]/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−[email protected]/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−[email protected]/G composite are revealed, which provides an important theoretical basis for the application of SIBs.