S-decorated Mo₂C as efficient catalyst for Li-O₂ battery system

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium-oxygen (Li-O2) batteries offer high theoretical energy density but suffer from poor kinetics, high overpotential, and instability.
• Current cathode materials limit the practical application of Li-O2 batteries.

Purpose of the Study:

• To enhance the electrochemical performance of Mo2C cathode materials for Li-O2 batteries.
• To investigate the effect of sulfur doping on Mo2C's electronic structure and catalytic activity.

Main Methods:

• Hydrothermal synthesis was used to prepare sulfur-modified Mo2C (S@Mo2C) cathode materials.
• Characterization techniques included X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS).
• Electrochemical performance was evaluated through specific capacity, overpotential, and cycling stability tests.

Main Results:

• S@Mo2C demonstrated a specific capacity of 3955 mA h g-1, significantly higher than commercial Mo2C (508 mA h g-1).
• The charge and discharge overpotential was reduced by 53.6% to 0.26 V.
• Capacity retention remained at 77.8% after 250 cycles, indicating improved stability.
• Sulfur doping formed a MoS2/MoS3 heterostructure, enhancing conductivity and oxygen reduction/precipitation (ORR/OER) activity.
• Sulfur doping promoted amorphous Li2O2 formation and inhibited insulating Li2O2 accumulation.

Conclusions:

• Sulfur doping is an effective strategy to improve the performance of Mo2C-based cathode materials for Li-O2 batteries.
• The S@Mo2C material exhibits superior electrochemical performance, including high capacity, low overpotential, and excellent cycle stability.
• This study provides a new pathway for designing efficient catalysts for advanced energy storage systems.