A Solid-Phase Conversion Sulfur Cathode with Full Capacity Utilization and Superior Cycle Stability for...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium-sulfur (Li-S) batteries offer high theoretical energy density but suffer from poor cyclability due to soluble polysulfide intermediates.
• Developing sulfur cathodes that suppress these intermediates and utilize sulfur efficiently remains a significant challenge.

Purpose of the Study:

• To engineer a solid-phase conversion sulfur cathode that enhances sulfur utilization and battery cycle life.
• To overcome the limitations of sulfur's insulating nature and polysulfide shuttle effect in Li-S batteries.

Main Methods:

• Fabrication of a coaxially assembled sulfur/carbon (CA-S/C) composite by encapsulating sulfur within CMK-3 carbon mesoporous channels.
• Utilizing vinyl carbonate (VC) as an electrolyte co-solvent to form a dense solid electrolyte interface (SEI) on the CA-S/C composite.
• Testing the electrochemical performance of the CA-S/C cathode in a Li-S battery system.

Main Results:

• The CA-S/C cathode demonstrated full capacity utilization (1667 mA h g⁻¹, ≈100%) and high rate capability (2.0 A g⁻¹).
• The battery exhibited excellent long-term cyclability, exceeding 500 cycles, even at a high sulfur loading of 75%.
• The in-situ formed SEI effectively suppressed polysulfide dissolution and enabled solid-phase conversion.

Conclusions:

• The proposed CA-S/C cathode strategy effectively addresses polysulfide issues and sulfur insulation in Li-S batteries.
• This approach shows significant promise for developing high-energy-density and stable Li-S batteries for practical applications.