N-Doped carbon encapsulating Bi nanoparticles derived from metal–organic frameworks for high-performance sodium-ion batteries

Abstract

Bismuth (Bi), as an alloy-based material, has been demonstrated as a promising anode for sodium-ion batteries (SIBs) due to its high theoretical capacity. However, the large volume change of the Bi anode during the sodiation/desodiation process results in poor cycling performance, which limits its practical application. In the present work, a simple one-step route was realized to fabricate Bi nanoparticles embedded into a N-doped carbon matrix (Bi@NC) by calcining Bi-containing metal–organic framework (Bi-MOF) precursors. Benefitting from the synergistic effect of Bi nanoparticles and the conductive N-doped carbon matrix, the composite can not only reduce the ion/electron diffusion pathways and enhance the reaction kinetics, but can also effectively alleviate the volume expansion during alloying/dealloying processes. As a result, the Bi@NC electrode displayed an excellent electrochemical performance with a superior rate capability of 86% capacity retention at 10 A g⁻¹ and a high capacity of 326.9 mA h g⁻¹ after 5000 cycles at 2 A g⁻¹. Furthermore, the assembled full cell with a Na₃V₂(PO₄)₃ cathode and a Bi@NC anode also delivered an impressive electrochemical performance with a high energy density of 125 W h kg⁻¹ (based on the total mass of cathode and anode materials). Furthermore, the sodium storage mechanism was also elucidated through in-depth fundamental investigation using in situ X-ray diffraction (XRD) and density functional theory (DFT) calculations.