Promoting the Rate Performances of Weakly Solvating Electrolyte-Based Lithium‒Sulfur Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium-sulfur (Li-S) batteries offer high theoretical energy density.
• Weakly solvating electrolytes (WSE) mitigate polysulfide shuttle but cause sluggish cathode kinetics.
• Degraded rate performance is a key challenge for WSE-based Li-S batteries.

Purpose of the Study:

• To systematically investigate the sluggish sulfur cathode kinetics in WSE-based Li-S batteries.
• To identify the primary kinetic limitations affecting capacity at high charge/discharge rates.
• To develop strategies for enhancing the rate performance of Li-S batteries in practical pouch cell formats.

Main Methods:

• Kinetic analysis of WSE-based Li-S battery cathodes.
• Polarization decoupling to identify dominant kinetic challenges.
• Development and implementation of a redox mediation strategy.
• Performance testing of 3 Ah and 5 Ah pouch cells.

Main Results:

• Sluggish cathode kinetics during charging limit specific discharge capacity at high rates.
• Activation polarization from polysulfide oxidation to elemental sulfur is the main kinetic hurdle.
• The proposed redox mediation strategy significantly accelerates polysulfide oxidation kinetics.
• Stable cycling at 0.2 C in 3 Ah pouch cells and 470 Wh kg⁻¹ energy density in 5 Ah pouch cells were achieved.

Conclusions:

• Understanding sulfur cathode kinetics in WSE is crucial for improving Li-S battery performance.
• Redox mediation is an effective strategy to overcome kinetic limitations in WSE-based Li-S batteries.
• This approach enables the development of high-energy-density and high-rate Li-S batteries for practical applications.