Electrocatalysis of polysulfide conversion by conductive RuO2 nano dots for lithium-sulfur batteries

Ni3FeN functionalized carbon nanofibers boosting polysulfide conversion for Li-S chemistry

Limiting the shuttle effect of polysulfides is an important means to realizing high energy density lithium-sulfur batteries (Li-S). In this study, an efficient electrocatalyst (CNFs@Ni3FeN) is synthesized by anchoring Ni3FeN in the carbon nanofibers (CNFs). The CNFs@Ni3FeN shows electrocatalytic activity and enhances the conversion of polysulfides. After assembling a battery, a high initial capacity (1452 mA h g-1) and favorable long-time cycling stability (100 cycles) with a capacity retention rate of 83% are obtained by the electrocatalysis of Ni3FeN. Compared with unmodified CNFs, the cycling stability of CNFs@Ni3FeN can be greatly improved. The catalytic mechanism is further deduced by X-ray photoelectron spectroscopy (XPS). Our work will inspire the rational design of CNFs@support hybrids for various electrocatalysis applications.

Embedding Fe3C and Fe3N on a Nitrogen-Doped Carbon Nanotube as a Catalytic and Anchoring Center for a High-Areal-Capacity Li-S Battery

The biggest obstacles of putting lithium-sulfur batteries into practice are the sluggish redox kinetics of polysulfides and serious "shuttle effect" under high sulfur mass loading and lean-electrolyte conditions. Herein, Fe₃C/Fe₃N@nitrogen-doped carbon nanotubes (NCNTs) as multifunctional sulfur hosts are designed to realize high-areal-capacity Li-S batteries. The Fe₃N and Fe₃C particles attached to NCNT can promote the conversion of polysulfides. Besides, NCNT can not only enhance the chemisorption of polysulfides but also increase the special surface area and electrical conductivity by constructing a three-dimensional skeleton network. Integrating the merits of high electrical conductivity, high catalytic activity, and strong chemical binding interaction with lithium polysulfides (LiPSs) to achieve in situ anchoring conversion, the Fe₃C/Fe₃N@NCNT multifunctional hosts realize high sulfur mass loading and accelerate redox kinetics. The novel Fe₃C/Fe₃N@NCNT/S composite cathode exhibits steady cycle ability and a high areal capacity of 9.10 mAh cm^-2 with a sulfur loading of 13.12 mg cm^-2 at 2.20 mA cm^-2 after 50 cycles.

MoO2 nanoparticles embedded in N-doped hydrangea-like carbon as a sulfur host for high-performance lithium–sulfur batteries

Lithium–sulfur batteries are considered to be promising energy storage devices owing to their high energy density, relatively low price and abundant resources. However, the low utilization of insulated active materials and shuttle effect have severely hindered the further development of lithium–sulfur batteries. Herein, MoO₂ nanoparticles embedded in N-doped hydrangea-like carbon have been synthesized by liquid-phase reaction followed by an annealing process and used as a sulfur host. The nitrogen-doped carbon matrix improves electrical conductivity and provides pathways for smooth electron and Li ion transfer to uniformly dispersed sulfur. Meanwhile, MoO₂ nanoparticles can absorb polysulfide ions by forming strong chemical bonds, which can effectively alleviate the polysulfide shuttling effect. These results showed a good rate performance: 1361, 1071, 925, 815 and 782 mA h g⁻¹ at the current densities of 0.1, 0.2, 0.5, 1 and 2 A g⁻¹, and capacity retention of 85% after 300 cycles at 1 A g⁻¹. The excellent performance was due to the synergistic effects of the polar MoO₂ and nitrogen-doped carbon matrix, which can effectively restrain and reutilize active materials by absorbing polysulfides and catalyzing the transformation of polysulfides.

Lithium–sulfur batteries are considered to be promising energy storage devices owing to their high energy density, relatively low price and abundant resources.