Binder-free 3D hierarchical Bi Nanosheet/CNTs arrays anode for full sodium-ion battery with high voltage above 4 V

Aiming to the repetitively large volume change and the inevitably loss of volumetric capacity of bismuth (Bi) based sodium-ion battery (SIB) during cycling, a binder-free Bi anode based on one-step electrochemical co-deposited three-dimensional Bi nanosheets and conductive carbon nanotube networks (Bi NS/CNTs) was developed. Compared with the sole Bi anode achieved via the same strategy, the co-deposition of 3D hierarchical Bi nanosheet/CNTs arrays manifests the strong interfacial adhesion and accommodates the volume change upon sodium alloying/dealloying. Such structural feature endows the Bi NS/CNTs anode a long-term cycling stability (383.72 mAh g−1 at 0.1 A g−1 after 200 cycles, 311.68 mAh g−1 at 1 A g−1 after 1000 cycles) and a good rate performance. A full SIB assembled with Bi NS/CNTs anode and Na3(VOPO4)2[email protected] cathode shows a high operating voltage (above 4 V) and a high energy density of 221.99 Wh kg−1, which outperforms many reported Bi-based analogues. This work may open a new opportunity for developing efficient SIB with high energy and good practicability.