Synergistic Site Engineering in Trimetallic Spinel Sulfides for High-Loading Lithium-Sulfur Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Lithium-sulfur batteries face performance limitations due to polysulfide shuttling and slow redox kinetics.
• Efficient catalysts are crucial for mediating polysulfide adsorption and conversion in these batteries.
• Precise control and mechanistic understanding of active sites are key for designing effective catalysts.

Purpose of the Study:

• To systematically investigate the distinct roles of octahedral and tetrahedral sites in spinel sulfides.
• To establish a dual-site cooperative mechanism for polysulfide adsorption and conversion.
• To provide rational design guidance for advanced lithium-sulfur battery catalysts.

Main Methods:

• Engineered site-selective doping in spinel sulfides using X-ray absorption spectroscopy.
• Fabrication of symmetric cells with tailored electrolytes and galvanostatic intermittent titration technique (GITT) analysis.
• Theoretical calculations to elucidate the electronic interactions and bonding mechanisms at active sites.

Main Results:

• Demonstrated site-selective doping to control octahedral and tetrahedral site occupation.
• Revealed stage-resolved catalytic roles: octahedral sites stabilize long-chain polysulfides, while tetrahedral sites convert short-chain polysulfides.
• Optimized Fe-Co-Ni trimetallic spinel sulfides achieved high initial capacity (1347.3 mAh g⁻¹) and excellent cycling stability (81.6% retention after 300 cycles at 0.2 C) with high sulfur loading (7.5 mg cm⁻²).

Conclusions:

• Established a dual-site cooperative adsorption-conversion mechanism in spinel sulfides.
• Provided fundamental insights into the distinct functions of octahedral and tetrahedral sites.
• Offered a rational design strategy for developing high-performance catalysts for lithium-sulfur batteries.