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Free-Radical Catalysis and Enhancement of the Redox Kinetics for Room-Temperature Sodium-Sulfur Batteries

journal contribution
posted on 12.06.2020, 00:00 authored by A Kumar, A Ghosh, M Forsyth, D R MacFarlane, S Mitra
Room-temperature sodium-sulfur (RT Na-S) batteries offer the potential for inexpensive stationary energy storage at the grid and local level. However, their practical performance remains far from theoretical due to sluggish reaction kinetics, which limits both their energy and their rate characteristics. To overcome this, a conceptually new mechanism is demonstrated on the basis of the catalysis by stabilized free-radical species, as indicated by electron spin resonance measurements, generated on the surface of a Na2S6 catholyte-infiltrated activated carbon cloth cathode. X-ray photoelectron spectroscopy characterizations reveal that free-radical catalysis promotes reduction to end-discharged products, via a surface-bound intermediate state, ACC-S3-. Due to this free-radical catalytic activity, our RT Na-S cell achieves a high nominal cell potential of 1.85 V. At a rate of 0.5 C, the Na-S cell delivers a high specific capacity of 866 mA h g(S)-1 and retains 678 mA h g(S)-1 after 700 cycles. The concept of a free-radical mechanism, as described herein, could be adapted to enhance the electrochemical kinetics of other energy storage devices that involve radical intermediate species.

History

Journal

ACS Energy Letters

Volume

5

Issue

6

Pagination

2112 - 2121

Publisher

American Chemical Society

Location

Washington, D.C.

eISSN

2380-8195

Language

eng

Publication classification

C1 Refereed article in a scholarly journal

Copyright notice

2020, American Chemical Society