Tandem Catalysis Overcomes the Rate-Determining Sulfur Conversion Cascade in Na─S Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Room-temperature sodium-sulfur (RT Na-S) batteries promise high energy density and low cost.
• Practical application is hindered by slow sulfur redox kinetics, especially late-stage conversions.
• Existing methods struggle to address the complex, multi-step reaction cascade in Na-S systems.

Purpose of the Study:

• To develop a step-targeted tandem catalysis strategy for RT Na-S batteries.
• To precisely regulate the rate-determining sulfur conversion cascade.
• To overcome kinetic limitations in Na-S battery cathodes.

Main Methods:

• Integration of atomically dispersed Fe-N4 sites and polar ZrO2 nanodomains within a carbon host.
• Density Functional Theory (DFT) calculations to elucidate step-specific catalytic mechanisms.
• Experimental kinetic analyses to validate the catalytic effect on sulfur conversion.

Main Results:

• Fe-N4 sites preferentially catalyze Na2S4→Na2S2 conversion, while ZrO2 drives Na2S2→Na2S conversion.
• Electronic coupling between catalysts creates a continuous activation landscape, accelerating the cascade.
• Achieved initial capacity of 1408 mAh g-1, over 10,000 cycles at 5 A g-1, and operation at -20°C.

Conclusions:

• Tandem catalysis effectively regulates multistep sulfur conversion in Na-S batteries.
• The strategy significantly enhances electrochemical performance, including capacity and cycling stability.
• This work presents a new paradigm for designing advanced Na-S battery cathodes.