The Design of the Ni₃N/Nb₄N₅ Heterostructure as Bifunctional Adsorption/Electrocatalytic Materials for Lithium–Sulfur Batteries

Abstract

Lithium–sulfur (Li-S) batteries are hindered by the sluggish electrochemical kinetics and poor reversibility of lithium polysulfides (LiPSs), which limits their practical energy density and cycle life. In order to address this issue, a novel Ni3N/Nb4N5 heterostructure was synthesized via electrospinning and nitridation as a functional coating for polypropylene (PP) separators. Adsorption experiments were conducted in order to ascertain the heterostructure’s superior affinity for LiPSs, thereby effectively mitigating their shuttling. Studies of Li2S nucleation demonstrated the catalytic role of the substance in accelerating the deposition kinetics of Li2S. Consequently, Li-S cells that employed the Ni3N/Nb4N5-modified separator were found to achieve significantly enhanced electrochemical performance, with the cells delivering an initial discharge capacity of 1294.4 mAh g−1 at 0.2 C. The results demonstrate that, after 150 cycles, the cells retained a discharge capacity of 796.2 mAh g−1, corresponding to a low capacity decay rate of only 0.25% per cycle. In addition, the rate capability of the cells was found to be improved in comparison to control cells with NiNb2O6-modified or pristine separators.

Keywords

• lithium–sulfur batteries
• heterostructure
• modified separator
• adsorption
• electrocatalysis