Novel Bismuth Nanoflowers Encapsulated in N‐Doped Carbon Frameworks as Superb Composite Anodes for High‐Performance Sodium‐Ion Batteries

Bismuth (Bi) has attracted attention as a promising anode for sodium-ion batteries (SIBs) owing to its suitable potential and high theoretical capacity. However, the large volumetric changes during cycling leads to severe degradation of electrochemical performance and limits its practical application. Herein, Bi nanoflowers are encapsulated in N-doped carbon frameworks to construct a novel Bi@NC composite via a facile solvothermal method and carbonization strategy. The well-designed composite structure endows the Bi@NC with uniformly dispersed Bi nanoflowers to alleviate the attenuation while the N-doped carbon frameworks improve the conductivity and ion transport of the whole electrode. As for sodium-ion half-cell, the electrode exhibits a high specific capacity (384.8 mAh g-1 at 0.1 A g-1 ) and excellent rate performance (341.5 mAh g-1 at 10 A g-1 ), and the capacity retention rate still remains at 94.9% after 5000 cycles at 10 A g-1 . Furthermore, the assembled full-cell with Na3 V2 (PO4 )3 cathode and Bi@NC anode can deliver a high capacity of 251.5 mAh g-1 at 0.1 A g-1 , and its capacity attenuates only 0.009% in each cycle after 2000 times at 5.0 A g-1 . This work offers a convenient, low-cost, and eco-friendliness approach for high-performance electrodes in the field of sodium ion electrochemical storage technology.