Co₂C/CoC₈ heterostructure towards polysulfide capture/conversion for advanced lithium-sulfur batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium-sulfur batteries (LSBs) face challenges due to slow redox kinetics and lithium polysulfide (LiPS) shuttle effects.
• These issues limit the practical application and cycle life of LSBs.

Purpose of the Study:

• To develop a nanostructured material combining cobalt carbides (Co2C/CoC8), nitrogen doping, and carbon black (NEC) to enhance LSB performance.
• To investigate the synergistic effects of Co2C/CoC8 heterostructure and nitrogen doping on LiPSs management and electrochemical activity.

Main Methods:

• Hydrothermal synthesis followed by heat treatment to prepare the Co2C/CoC8/NEC nanostructured material.
• Fabrication of LSBs using Co2C/CoC8/NEC as an electrocatalyst in the separator and cathode.
• Electrochemical testing, including cycling performance, rate capability, and long-term stability tests.
• Density functional theory (DFT) calculations to elucidate the mechanisms of Co2C and CoC8.

Main Results:

• The Co2C/CoC8/NEC material demonstrated enhanced LiPSs trapping and catalytic conversion.
• LSBs equipped with Co2C/CoC8/NEC showed high initial discharge capacity (1131 mAh g-1 at 0.5 C) and excellent capacity retention (86% after 300 cycles).
• Remarkable long-term stability was achieved with a decay rate of 0.023% per cycle over 1500 cycles at 1 C, even under demanding conditions (high sulfur loading, lean electrolyte).

Conclusions:

• The Co2C/CoC8/NEC nanostructure effectively addresses LiPS shuttle and redox kinetics issues in LSBs.
• This work highlights the potential of transition metal carbides (TMCs) in designing high-performance LSBs.
• The developed strategy offers a promising pathway for advancing secondary battery technologies.