Developing high-power Li||S batteries via transition metal/carbon nanocomposite electrocatalyst engineering

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Volcano plots describe thermodynamic trends for electrocatalysts in the sulfur reduction reaction (SRR).
• A kinetic trend for SRR at high current rates is currently lacking, hindering the development of high-power lithium-sulfur (Li||S) batteries.
• Understanding kinetic variations is crucial for optimizing battery performance.

Purpose of the Study:

• To establish a kinetic trend for the sulfur reduction reaction (SRR) that correlates polysulfide concentrations with kinetic currents.
• To provide a guideline for designing efficient electrocatalysts for high-power Li||S batteries.
• To elucidate the role of orbital occupancy in transition metal catalysts for SRR kinetics.

Main Methods:

• Utilized Le Chatelier's principle to establish the SRR kinetic trend.
• Employed synchrotron X-ray adsorption spectroscopy and molecular orbital computations to investigate catalyst properties.
• Designed and tested a nanocomposite electrocatalyst (carbon material with CoZn clusters) in Li||S coin cells.

Main Results:

• A novel SRR kinetic trend was successfully established, linking polysulfide levels to catalytic current.
• Orbital occupancy in transition metal catalysts was identified as key to controlling polysulfide concentrations and predicting SRR kinetics.
• The designed CoZn/carbon electrocatalyst enabled Li||S cells (5 mg cm⁻² S loading) to cycle for 1,000 cycles at 8 C with ~75% capacity retention.

Conclusions:

• The developed kinetic trend provides a predictive tool for designing advanced electrocatalysts for the SRR.
• The CoZn/carbon nanocomposite demonstrates excellent performance, achieving high specific power (26,120 W kg⁻¹) and energy (1,306 Wh kg⁻¹).
• This work significantly advances the development of high-performance, high-power Li||S batteries.