Rooting bismuth oxide nanosheets into porous carbon nanoboxes as a sulfur immobilizer for lithium–sulfur batteries

Abstract

Building a sulfur host cathode with high electronic transfer ability and strong confinement effect towards intermediate polysulfide is pivotal to develop advanced lithium–sulfur (Li–S) batteries. Herein, a MOF-driven strategy has been employed to synthesize a hierarchical architecture constructed by rooting bismuth oxide nanosheets into Co/N-co-doped porous carbon nanoboxes (Bi₂O₃@Co/N-PC). After a process of sulfur infiltration, the hierarchical architecture turns into a hybrid composed of sulfur embedded within the Bi₂O₃@Co/N-PC host (Bi₂O₃@Co/N-PC@S). When used as the cathode material for Li–S batteries, the as-prepared Bi₂O₃@Co/N-PC@S not only exhibits a high initial discharge capacity of 1302 mA h g⁻¹ at a current density of 0.25 C, but also maintains a capacity of 732 mA h g⁻¹ after 500 cycles at the current density of 1.5 C. Moreover, the high rate test also demonstrates its exceptional rate capability with a capacity as high as 451 mA h g⁻¹ after 1500 cycles at the current density of 10 C. Such excellent performance can be attributed to the high conductivity and favourable surface structure of the Co/N-doped carbon framework as well as its strong charge coupling with bismuth oxide nanosheets, resulting in low polarization, fast redox reaction kinetics, and high immobilization ability towards intermediate polysulfide.