An Effective Single-Atom Catalytic Descriptor for Accelerating Sulfur Reduction Reaction in Lithium-Sulfur Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• The Li₂S₂-to-Li₂S transition is a key bottleneck in lithium-sulfur battery (LSB) performance, affecting reaction kinetics and energy efficiency.
• Single-atom catalysts (SACs) offer potential for improving this process, but rational design is limited by a lack of intrinsic electronic descriptors.
• Current methods often rely on polysulfide adsorption configurations, which may not fully capture catalytic activity.

Purpose of the Study:

• To establish a universal electronic descriptor linking atomic-scale properties to macroscopic catalytic performance in sulfur electrochemistry.
• To enable rational design of single-atom catalysts for lithium-sulfur batteries (LSBs) and sodium-sulfur batteries (NSBs).
• To provide atomic-level insights into the Li₂S₂-to-Li₂S conversion mechanism.

Main Methods:

• Introduction of a universal electronic descriptor, θ-χ, defined as the difference between valence electron count (θ) and electronegativity (χ) of transition metal centers.
• Systematic screening of 3d/4d-transition metal SACs on nitrogen-doped graphene (TM@NG) using the θ-χ descriptor.
• Computational analysis correlating the descriptor with energy barriers for Li₂S₂-to-Li₂S conversion and interfacial charge redistribution.

Main Results:

• The θ-χ descriptor strongly correlates with the energy barriers for Li₂S₂-to-Li₂S conversion, achieving R² ≈ 0.90.
• Descriptor-guided screening identified V@NG, Ti@NG, and Nb@NG as high-performing catalysts, with Mo@NG showing superior activity.
• The θ-χ descriptor demonstrated transferability to sodium-sulfur batteries (NSBs), accurately predicting Na₂S₂-to-Na₂S kinetics without recalibration.

Conclusions:

• The θ-χ descriptor provides a powerful tool for electronic-structure-driven catalyst design, moving beyond configuration-dependent simulations.
• This approach facilitates the rational development of efficient SACs for both LSBs and NSBs.
• The findings offer fundamental insights into sulfur electrochemistry, paving the way for next-generation battery technologies.