A chemically stabilized sulfur cathode for lean electrolyte lithium sulfur batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium-sulfur batteries (LSBs) offer high energy density but suffer from polysulfide dissolution and low Coulombic efficiency, necessitating excess electrolytes and lithium metal.
• Current quasi-solid-state LSBs have limitations in sulfur loading and utilization, hindering cell-level energy density.
• The shuttle effect of polysulfides and low Coulombic efficiency are key challenges for practical LSBs.

Purpose of the Study:

• To develop a high-performance cathode material for lithium-sulfur batteries with increased sulfur loading and utilization.
• To overcome the limitations of polysulfide dissolution and the shuttle effect in LSBs.
• To enhance the energy density and cycle life of LSBs under lean electrolyte conditions.

Main Methods:

• Dispersing sulfur at a molecular level within an oxygen-rich dense carbon host, creating strong C-S and O-S chemical interactions.
• Utilizing an all-fluorinated organic lean electrolyte.
• Investigating the solid-state lithiation/delithiation reaction after solid electrolyte interphase formation.

Main Results:

• Achieved a high sulfur loading of 60 wt % and sulfur utilization of approximately 87%.
• The chemically stabilized C/S composite demonstrated a high reversible capacity of 541 mAh·g⁻¹ (total composite weight).
• Maintained high performance for 200 cycles under lean electrolyte conditions, achieving an energy density of 974 Wh·kg⁻¹.

Conclusions:

• The developed chemical bonding-stabilized C/S composite effectively suppresses the shuttle reaction and enhances LSB performance.
• This material is a promising cathode for high-energy and long-cycle-life lithium-sulfur batteries.
• The molecular-level dispersion and chemical stabilization are key to overcoming LSB limitations.