Tuning the Band Structure of MoS₂ via Co₉S₈@MoS₂ Core–Shell Structure to Boost Catalytic Activity for Lithium–Sulfur Batteries

Abstract

The introduction of a dual-functional interlayer into lithium−sulfur batteries (LSBs) provides many opportunities for restraining the "shuttle effect" and enhancing sluggish sulfur conversion kinetics. Tuning the band structure of the metal sulfide provides an opportunity to enhance its catalytic activity, which plays an important role in suppressing the "shuttle effect" of lithium polysulfides (LiPSs) in LSBs.Here were present a Co 9 S 8 @MoS 2 core−shell heterostructure anchored to a carbon nanofiber (Co 9 S 8 @MoS 2 /CNF), developed as an interlayer for suppressing the shuttle effect of LiPSs. The fabricated composite heterostructure is determined to be an effective alternative material that combines the synergistic relationship between chemisorption and electrochemical catalysis. We find that the band structure of the MoS 2 shell can be effectively tuned by the Co 9 S 8 core and that the Co 9 S 8 @MoS 2 /CNF can capture the LiPSs, providing excellent catalytic ability to convert LiPSs into Li 2 S 2 , with subsequent transformation from Li 2 S 2 to Li 2 S. Importantly, high capacities of 1002 and 986 mAh g −1 can be retained after 50 cycles with high-sulfur loadings of 6 and 10 mg cm −2 . Our results highlight the design of an atomic-scale heterostructure as a multifunctional interlayer providing a synergistic relationship between adsorption and catalysis. The net result is an effective retardation of the shuttling of LiPSs and an enhancement of the electrochemical redox reactions of LiPSs. This work shows great promise toward the development of practical applications of LSBs.

A Tandem Electrocatalysis of Sulfur Reduction by Bimetal 2D MOFs

“…[5,6] The catalyzed sulfur redox reaction showed faster conversion kinetics, especially for the conversion of soluble LiPSs into the insoluble final products, thus preventing the continuous accumulation of LiPSs in electrolyte that is responsible for the shuttle effect. [7,8] An increasing number of electrocatalysts have been applied to Li-S batteries, [5,[9][10][11][12] however, systematic study on the kinetic and underlying basis to evaluate the exact role of catalyst addressing the PS shuttling issues is still overlooked. The classic electrocatalysis process is mostly referred to as heterogeneous catalytic reaction [13] -catalyzing a specific reaction instead of a series of reactions-as exemplified by the wellestablished electrocatalysis in fuel cells and water splitting such as the oxygen reduction reaction, oxygen evolution reaction (OER), and hydrogen evolution reaction.…”

Rational Design of the Lotus‐Like N‐Co2VO4‐Co Heterostructures with Well‐Defined Interfaces in Suppressing the Shuttle Effect and Dendrite Growth in Lithium–Sulfur Batteries

“…As shown in Figure 3e, the N-Co 2 VO 4 -Co illustrates four valence states of Co (778.8 and 793.8 eV), Co 2+ (780.2 and 796.1 eV), Co 3+ (782.6 and 797.6 eV), and satellite Co (786.8 and 801.8 eV). [28] These results strongly manifest that nitrogen was successfully doped in the Co 2 VO 4 after annealing in the Ar/NH 3 atmosphere. Meanwhile, compared with that of the Co 2 VO 4 -Co, a new fitted peak at 531.8 eV is found in the high-resolution spectrum of O 1s, which could be attributed to the contribution from defective oxygen in the N-Co 2 VO 4 -Co. [15,29] The EPR spectra of N-Co 2 VO 4 -Co further show a stronger signal of g = 2.004 compared to that of Co 2 VO 4 -Co, implying that lots of vacancies were generated after the annealing treatment in Ar/NH 3 (Figure 4a).…”

Polysulfide Filter and Dendrite Inhibitor: Highly Graphitized Wood Framework Inhibits Polysulfide Shuttle and Lithium Dendrites in Li–S Batteries

“…g) Comparison of the areal capacities obtained in this work and reported for cells with other kinds of interlayers. [ 64–76 ]…”

“…As shown in Figure 2g, the cell with the GWF interlayer showed an areal capacity of 4.2 mAh cm −2 , which is a considerable value compared with other kinds of interlayers. [ 64–76 ]…”