Room-Temperature Sodium-Sulfur Batteries: Rules for Catalyst Selection and Electrode Design

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Room-temperature sodium-sulfur (RT Na-S) batteries offer high theoretical energy density but face challenges in reaction kinetics and polysulfide management.
• Developing efficient catalysts is crucial for enhancing the electrochemical performance and practical application of RT Na-S batteries.

Purpose of the Study:

• To establish theoretical principles for selecting catalysts based on interfacial interactions with polysulfides.
• To design and synthesize a dual-functioning host material for RT Na-S batteries.
• To investigate the catalyst's effect on polysulfide anchoring, conversion kinetics, and sodium anode behavior.

Main Methods:

• Theoretical calculations of catalyst-polysulfide interfacial interactions (adsorption, ion migration, electronic concentration).
• Synthesis of Molybdenum Nitride within Carbon Nanofibers (MoN@CNFs) as a dual-functioning host.
• In situ characterizations and finite element simulation to study sodium deposition and dendrite inhibition.
• Electrochemical testing of RT Na-S batteries with MoN@CNFs.

Main Results:

• MoN@CNFs effectively anchor polysulfides and accelerate their conversion reaction kinetics.
• The MoN@CNFs facilitate uniform sodium deposition and suppress dendrite growth on the sodium anode.
• The prepared RT Na-S battery achieved a high reversible capacity of 990 mAh g^-1 at 0.2 A g^-1 after 100 cycles.
• A long cycle life exceeding 1500 cycles at 2 A g^-1 was demonstrated.
• High areal capacity of 2.5 mAh cm^-2 was achieved even with a high sulfur loading of 5 mg cm^-2.

Conclusions:

• Theoretical guidance based on interfacial interactions is effective for catalyst selection in RT Na-S batteries.
• MoN@CNFs serve as a promising dual-functioning material for enhancing both cathode and anode performance in RT Na-S batteries.
• The developed strategy significantly improves the electrochemical performance, enabling practical applications of RT Na-S batteries.