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

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.

Automated summary

In this study, Bi nanoparticles embedded in N-doped carbon matrix composite Bi@NC were successfully prepared using a simple one-step method. The composite exhibited excellent electrochemical performance, effectively alleviating the volume expansion issue during sodiation/desodiation processes, and showing outstanding cycling stability and rate performance.