Title: Electrochemistry of the NaI-AlBr ₃ Molten Salt System: A Redox-Active, Low-Temperature Molten Salt Electrolyte

Abstract

NaI-AlBr ₃ is a very appealing low melting temperature (<100 °C), salt system for use as an electrochemically-active electrolyte. This system was investigated for its electrochemical and physical properties with focus to energy storage considerations. A simple phase diagram was generated; at >100 °C, lower NaI concentrations had two partially miscible liquid phases, while higher NaI concentrations had solid particles. Considering the fully molten regime, electrical conductivities were evaluated over 5–25 mol% NaI and 110 °C–140 °C. Conductivities of 6.8–38.9 mS cm ⁻¹ were observed, increasing with temperature and NaI concentration. Effective diffusion coefficients of the I ⁻ /I ₃ ⁻ redox species were found to decrease with both increasing NaI concentration and increasing applied potential. Regardless, oxidation current density at 3.6 V vs Na/Na ⁺ was observed to increase with increasing NaI concentration over 5–25 mol%. Finally, the critical interface between the molten salt electrolyte and electrode materials was found to significantly affect reaction kinetics. When carbon was used instead of tungsten, an adsorbed species, most likely I ₂ , blocked surface sites and significantly decreased current densities at high potentials. This study shows the NaI-AlBr ₃ system offers an attractive, low-temperature molten salt electrolyte that could be usefulmore » to many applied systems, though composition and electrode material must be considered.« less

Authors:

Percival, Stephen J. ;

• Search DOE PAGES for author "Percival, Stephen J."
• Search DOE PAGES for ORCID "0000-0003-2067-7468"

Lee, Rose Y. ;

• Search DOE PAGES for author "Lee, Rose Y."
• Search DOE PAGES for ORCID "0000-0002-2658-7220"

Gross, Martha M. ;

• Search DOE PAGES for author "Gross, Martha M."
• Search DOE PAGES for ORCID "0000-0002-3283-6406"

Peretti, Amanda S.; Small, Leo J. ;

• Search DOE PAGES for author "Small, Leo J."
• Search DOE PAGES for ORCID "0000-0003-0404-6287"

Spoerke, Erik D.

• Search DOE PAGES for author "Spoerke, Erik D."
• Search DOE PAGES for ORCID "0000-0003-2286-2560"

Publication Date:

Thu Mar 11 00:00:00 EST 2021

Research Org.:

Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Sponsoring Org.:

USDOE Office of Electricity (OE), Advanced Grid Research & Development. Power Systems Engineering Research; USDOE National Nuclear Security Administration (NNSA)

OSTI Identifier:

1835446

Alternate Identifier(s):

OSTI ID: 1772937

Report Number(s):

SAND-2021-3076J
Journal ID: ISSN 0013-4651

Grant/Contract Number:  

AC04-94AL85000; NA0003525

Resource Type:

Published Article

Journal Name:

Journal of the Electrochemical Society

Additional Journal Information:

Journal Name: Journal of the Electrochemical Society Journal Volume: 168 Journal Issue: 3; Journal ID: ISSN 0013-4651

Publisher:

The Electrochemical Society

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY