rGO@TiO_2-x Schottky heterojunction for enhanced bidirectional catalysis in polysulfide conversion

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Lithium-sulfur batteries (LSBs) suffer from poor cycling performance and low energy efficiency due to lithium polysulfide (LiPS) shuttling and slow conversion kinetics.
• Developing effective catalysts is crucial to overcome these limitations and improve LSBs' practical viability.

Purpose of the Study:

• To synthesize and characterize a novel hierarchically structured nanocomposite catalyst for LSBs.
• To investigate the catalytic activity of the nanocomposite in inhibiting LiPS shuttling and enhancing redox kinetics.
• To evaluate the electrochemical performance of LSBs utilizing the developed catalyst.

Main Methods:

• Surfactant-directed hydrothermal growth followed by dopamine-protected pyrolysis to synthesize the N-doped reduced graphene oxide (rGO)/TiO2-x nanocomposite.
• Formation of 2D/0D Schottky heterojunctions (rGO/TiO2-x) via interfacial N-Ti and C-Ti bonding.
• Density functional theory (DFT) calculations and in situ Raman characterization to study LiPS interaction and redox kinetics.

Main Results:

• The rGO/TiO2-x nanocomposite effectively inhibits LiPS shuttling and accelerates redox kinetics.
• Achieved high sulfur cathode utilization and improved overall reversibility in LSBs.
• Demonstrated a high initial specific capacity of 1010 mAh g⁻¹ at 0.2C with 86.4% retention over 100 cycles at high sulfur loading and low electrolyte/sulfur ratio.

Conclusions:

• The developed rGO/TiO2-x nanocomposite acts as a bidirectional catalyst, significantly improving LSB performance.
• The unique Schottky heterojunction structure is key to suppressing LiPS shuttling and enhancing electrochemical kinetics.
• The LSBs show great potential for practical applications, as evidenced by powering an LED screen.