Unraveling the Coupling Effect between Cathode and Anode toward Practical Lithium-Sulfur Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Localized reaction heterogeneity in sulfur cathodes and uneven lithium deposition on lithium anodes hinder practical lithium-sulfur (Li-S) battery performance.
• Existing research often optimizes the sulfur cathode or lithium anode independently, neglecting their coupled relationship.

Purpose of the Study:

• To establish a comprehensive understanding of the coupled relationship between sulfur cathode and lithium anode in Li-S batteries.
• To develop a descriptor for rational structural design of Li-S battery electrodes.
• To engineer a scalable electrode structure for enhanced performance under practical conditions.

Main Methods:

• Inspired by the Butler-Volmer equation, a binary descriptor (I_BD) was identified, incorporating mass-transport (I_mass) and charge-transfer (I_charge) indices.
• The relationship between I_BD and lithium anode morphological evolution was established.
• A scalable electrode with interpenetrated flow channels was designed and fabricated.

Main Results:

• The developed binary descriptor (I_BD) guided the rational structural design of the sulfur cathode.
• The engineered electrode demonstrated efficient mass/charge transfer, full sulfur utilization, and mechanical elasticity.
• Homogenous local current densities and reduced reaction heterogeneity were observed at both cathode and anode.
• Achieved impressive energy densities of 318 Wh kg⁻¹ and 473 Wh L⁻¹ in an Ah-level pouch cell.

Conclusions:

• The study presents a promising paradigm for understanding and optimizing the cathode-anode interaction in Li-S batteries.
• The I_BD descriptor facilitates the design of high-energy, practical Li-S batteries by addressing coupled reaction heterogeneity.
• The engineered electrode structure offers a scalable solution for improving the stability and energy density of Li-S batteries.