Nitrogen/Sulfur Co-doped Nb2O5-modified biomass-derived porous carbon as a high-performance cathode for lithium–sulfur batteries

Lithium–sulfur (Li–S) batteries are regarded as one of the most promising next-generation energy storage technologies owing to their ultrahigh theoretical specific capacity and energy density. Nevertheless, their practical application is still hampered by severe polysulfide shuttling, poor electrode conductivity, and large volume variation during cycling. Herein, medical-grade cotton wool was employed as a sustainable carbon precursor to construct a porous carbon framework, followed by solvothermal and thermal treatment to obtain orthorhombic Nb 2 O 5 /PC (T-Nb 2 O 5 /PC). Furthermore, thiourea was introduced as a dopant source to achieve nitrogen and sulfur co-doping, generating nitrogen/sulfur co-doped T-Nb 2 O 5 -modified biomass-derived porous carbon (NS-T-Nb 2 O 5 /PC) with synergistic catalytic activity and enlarged surface area. Comprehensive structural analyses reveal that N/S co-doping not only induces abundant lattice defects and active sites but also optimizes the electronic configuration and ion-transport channels while preserving the crystal integrity. Benefiting from these features, the NS-T-Nb 2 O 5 -1/PC/S electrode delivers a high initial discharge capacity of 1263.5 mAh g −1 at 0.1 C and maintains 685.5 mAh g −1 after 200 cycles, together with outstanding reversibility and rapid kinetics in the 0.1–1 C range. This work offers an effective strategy to regulate the electronic structure and interfacial chemistry of Nb 2 O 5 -PC host via in situ heteroatom doping, thereby enabling suppressed shuttle effect and enhanced Li–S battery performance.