Highly Solvating Electrolytes with Core-Shell Solvation Structure for Lean-Electrolyte Lithium-Sulfur Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Lithium-sulfur batteries offer high theoretical energy density but face challenges with low sulfur utilization and electrolyte instability.
• Existing highly solvating electrolytes (HSEs) struggle with long-term stability of sulfur redox reactions and lithium metal anodes.
• Addressing these limitations is crucial for advancing practical lithium-sulfur battery technology.

Purpose of the Study:

• To develop a novel core-shell solvation structured HSE for improved lithium-sulfur battery performance.
• To enhance sulfur utilization and stability under lean electrolyte conditions.
• To enable stable cycling of lithium metal anodes in conjunction with sulfur cathodes.

Main Methods:

• Formulation of a unique core-shell solvation structured HSE using ether-based solvents and a phosphoramide co-solvent.
• Investigating the electrolyte's solvation structure and its impact on radical intermediates and anode stability.
• Electrochemical testing of lithium-sulfur cells with high sulfur loading and low electrolyte-to-sulfur ratios.

Main Results:

• The core-shell structure effectively confines the co-solvent, preventing detrimental reactions with the lithium metal anode.
• Prolonged stability of the [S3]•− radical intermediate was achieved, facilitating rapid, solution-based sulfur redox reactions.
• Achieved a high capacity of 864 mAh gsulfur−1 at a sulfur loading of 5.5 mgsulfur cm−2 and E/S ratio of 4 μL mgsulfur−1.
• Demonstrated steady cycling of a 2.71-A h pouch cell with a specific energy of 307 Wh kg−1.

Conclusions:

• Tuning the electrolyte solvation structure is a fundamental strategy for simultaneously improving sulfur redox reaction and lithium metal anode stability.
• The developed core-shell structured HSE offers a promising pathway for high-energy-density lithium-sulfur batteries.
• This work provides critical insights into the coupled electrode-electrolyte chemistry governing metal-sulfur battery performance.