Bi/Bi ₂ O ₃ Nanoparticles In Situ Embedded in Carbon as Anode Materials for Fast and Long‐Lasting Sodium–Ion Storage

ABSTRACT Bismuth anode materials are considered promising anode candidates for sodium–ion batteries (SIBs) due to their high theoretical capacity and appropriate working potential. Nevertheless, the significant volume expansion that occurs during the cycling process restricts its broader application in sodium–ion storage. Herein, Bi/Bi 2 O 3 nanoparticles in situ embedded in a layered carbon framework (Bi/Bi 2 O 3 ‐C‐ X , where X represents pyrolysis temperature) have been designed, which can effectively promote interfacial charge transfer, shorten the Na + diffusion path, and alleviate volume expansion during the sodiation/desodiation processes. The Bi/Bi 2 O 3 ‐C‐700 layered composite electrode has a capacity of 320.1 mAh g −1 after 2000 cycles at 5 A g −1 , and an average capacity decay of 0.0284% per cycle. In addition, it still maintains a high capacity of 365.2 mAh g −1 after 40 cycles at a low temperature of −20°C. The mechanism of the Bi/Bi 2 O 3 ‐C‐700 composite electrode was analyzed by in situ XRD. The results indicated that conversion and alloying reactions occurred during the sodiation/desodiation processes. Furthermore, the assembled Na 3 V 2 (PO 4 ) 3 //Bi/Bi 2 O 3 ‐C‐700 full‐cell maintains a high capacity of 298.4 mAh g −1 after 200 cycles at 1 A g −1 . This study provides new insights into developing fast and long‐lasting bismuth anodes for SIBs.