High-Performance Lithium-Sulfur Batteries: Medium-Entropy Alloys Embedded in CeO₂ for Polysulfide/Sulfide...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Slow kinetics of sulfur reduction (SRR) and Li2S oxidation (SOR) reactions hinder lithium-sulfur battery (LSB) practical applications.
• Developing efficient catalysts is crucial for overcoming these kinetic limitations.

Purpose of the Study:

• To design and synthesize a functional interlayer for LSBs.
• To investigate the catalytic mechanism of the interlayer on SRR and SOR.
• To evaluate the electrochemical performance of LSBs utilizing the developed interlayer.

Main Methods:

• Fabrication of a functional interlayer comprising hydroxylated carbon nanotubes, NiCoMoIr medium-entropy alloys, and CeO2.
• Electrochemical characterization including cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy.
• Analysis of the catalytic mechanism through experimental data interpretation.

Main Results:

• The interlayer demonstrated a bidirectional catalytic mechanism involving Ni, Ir, Co, Mo, and CeO2.
• Ni and Ir promoted SRR, while Co and Mo promoted the conversion of Li2S to Li2S6.
• CeO2 provided synergistic effects, enhancing both SRR and SOR kinetics.
• The LSB with the interlayer achieved a specific capacity of 1535.7 mAh g-1 at 0.2 C and maintained a low decay rate of 0.051% per cycle over 1000 cycles at 1 C.
• A 2 Ah pouch cell exhibited an energy density of 436.4 Wh kg-1 with a capacity decay rate of 0.039% per cycle after 800 cycles.

Conclusions:

• The developed functional interlayer effectively catalyzes the sluggish kinetics of SRR and SOR in LSBs.
• The synergistic catalytic effects of the multi-element alloy and CeO2 contribute to enhanced battery performance and longevity.
• The results indicate significant potential for practical applications of high-performance LSBs.