Enhancing Bidirectional Sulfur Conversion Through p-d Orbital Hybridization via Vacancy Engineering

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Lithium-sulfur batteries (LSBs) offer high energy density but suffer from the shuttle effect and slow redox kinetics.
• These limitations hinder their practical application in energy storage.

Purpose of the Study:

• To develop a strategy for accelerating polysulfide kinetics in LSBs.
• To investigate the role of oxygen vacancy concentration in CoWO4 as a catalyst.

Main Methods:

• Experimental synthesis and characterization of CoWO4 with modulated oxygen vacancies (CWO-M).
• Density functional theory (DFT) calculations to understand catalytic mechanisms.
• Electrochemical testing of CWO-M/S cathodes in LSBs.

Main Results:

• CWO-M exhibits optimal adsorption energy and catalytic capacity for polysulfides due to p-d orbital hybridization.
• Demonstrated a bidirectional catalytic effect, accelerating both sulfur reduction and Li2S oxidation.
• Achieved excellent rate performance (768 mAh g⁻¹ at 2 C) and high capacity retention (91.1% after 100 cycles at 0.2 C).
• Stable cycling with high capacity (4 mAh cm⁻²) at high sulfur loading (8.02 mg cm⁻²) and low E/S ratio (8 µL mg S⁻¹).

Conclusions:

• Modulating oxygen vacancy concentration in CoWO4 provides effective bidirectional catalysis for LSBs.
• CWO-M significantly enhances the electrochemical performance and stability of LSBs.
• This approach offers valuable insights for designing advanced catalysts for high-performance LSBs.