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On the Reversibility and Fragility of Sodium Metal Electrodes

On the Reversibility and Fragility of Sodium Metal Electrodes Metallic sodium is receiving renewed interest as a battery anode material because the metal is earth‐abundant, inexpensive, and offers a high specific storage capacity (1166 mAh g−1 at −2.71 V vs the standard hydrogen potential). Unlike metallic lithium, the case for Na as the anode in rechargeable batteries has already been demonstrated on a commercial scale in high‐temperature Na||S and Na||NiCl2 secondary batteries, which increases interest. The reversibility of room temperature sodium anodes is investigated in galvanostatic plating/stripping reactions using in situ optical visualization and galvanostatic polarization measurements. It is discovered that electronic disconnection of mossy metallic Na deposits (“orphaning”) is a dominant source of anode irreversibility in liquid electrolytes. The disconnection is shown by means of direct visualization studies to be triggered by a root‐breakage process during the stripping cycle. As a further step toward electrode designs that are able to accommodate the fragile Na deposits, electrodeposition of Na is demonstrated in nonplanar electrode architectures, which provide continuous and morphology agnostic access to the metal at all stages of electrochemical cycling. On this basis, nonplanar Na electrodes are reported, which exhibit exceptionally high levels of reversibility (Coulombic efficiency >99.6% for 1 mAh cm−2 Na throughput) in room‐temperature, liquid electrolytes. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Advanced Energy Materials Wiley

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References (23)

Publisher
Wiley
Copyright
© 2019 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim
ISSN
1614-6832
eISSN
1614-6840
DOI
10.1002/aenm.201901651
Publisher site
See Article on Publisher Site

Abstract

Metallic sodium is receiving renewed interest as a battery anode material because the metal is earth‐abundant, inexpensive, and offers a high specific storage capacity (1166 mAh g−1 at −2.71 V vs the standard hydrogen potential). Unlike metallic lithium, the case for Na as the anode in rechargeable batteries has already been demonstrated on a commercial scale in high‐temperature Na||S and Na||NiCl2 secondary batteries, which increases interest. The reversibility of room temperature sodium anodes is investigated in galvanostatic plating/stripping reactions using in situ optical visualization and galvanostatic polarization measurements. It is discovered that electronic disconnection of mossy metallic Na deposits (“orphaning”) is a dominant source of anode irreversibility in liquid electrolytes. The disconnection is shown by means of direct visualization studies to be triggered by a root‐breakage process during the stripping cycle. As a further step toward electrode designs that are able to accommodate the fragile Na deposits, electrodeposition of Na is demonstrated in nonplanar electrode architectures, which provide continuous and morphology agnostic access to the metal at all stages of electrochemical cycling. On this basis, nonplanar Na electrodes are reported, which exhibit exceptionally high levels of reversibility (Coulombic efficiency >99.6% for 1 mAh cm−2 Na throughput) in room‐temperature, liquid electrolytes.

Journal

Advanced Energy MaterialsWiley

Published: Oct 1, 2019

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