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Elucidating Zn and Mg Electrodeposition Mechanisms in Nonaqueous Electrolytes for Next-Generation Metal Batteries

Ta, Kim and See, Kimberly A. and Gewirth, Andrew A. (2018) Elucidating Zn and Mg Electrodeposition Mechanisms in Nonaqueous Electrolytes for Next-Generation Metal Batteries. Journal of Physical Chemistry C, 122 (25). pp. 13790-13796. ISSN 1932-7447. http://resolver.caltech.edu/CaltechAUTHORS:20180608-085634860

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Abstract

Cyclic voltammetry and linear sweep voltammetry with an ultramicroelectrode (UME) were employed to study Zn and Mg electrodeposition and the corresponding mechanistic pathways. CVs obtained at a Pt UME for Zn electroreduction from a trifluoromethylsulfonyl imide (TFSI^–) and chloride-containing electrolyte in acetonitrile exhibit current densities that are scan rate independent, as expected for a simple electron transfer at a UME. However, CVs obtained from three different Mg-containing electrolytes in THF exhibit an inverse dependence between scan rate and current density. COMSOL-based simulation suggests that Zn electrodeposition proceeds via a simple one-step, two-electron transfer (E) mechanism. Alternatively, the Mg results are best described by invoking a chemical step prior to electron transfer: a chemical–electrochemical (CE) mechanism. The chemical step exhibits an activation energy of 51 kJ/mol. This chemical step is likely the disproportionation of the chloro-bridged dimer [Mg_2(μ–Cl)_3·6THF]^+ present in active electrodeposition solutions. Our work shows that Mg deposition kinetics can be improved by way of increased temperature.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1021/acs.jpcc.8b00835DOIArticle
https://pubs.acs.org/doi/suppl/10.1021/acs.jpcc.8b00835PublisherSupporting Information
ORCID:
AuthorORCID
See, Kimberly A.0000-0002-0133-9693
Gewirth, Andrew A.0000-0003-4400-9907
Additional Information:© 2018 American Chemical Society. Received: January 24, 2018; Revised: February 25, 2018; Published: February 26, 2018. This work was supported as part of the Joint Center for Energy Storage, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Research. The authors thank Dr. Sang-Don Han for assistance with drying the Zn(TFSI)_2 compound, Tabitha Miller and Prof. Alison Fout for assistance with drying the solvents, and Dr. Burton H. Simpson and Dr. Zachary J. Barton for initial assistance with COMSOL simulation. K.A.S. acknowledges postdoctoral funding from the St. Elmo Brady Future Faculty Postdoctoral Fellowship. This work was carried out in part at the Visualization Laboratory in the Beckman Institute, University of Illinois at Urbana–Champaign. The authors declare no competing financial interest.
Funders:
Funding AgencyGrant Number
Department of Energy (DOE)UNSPECIFIED
St. Elmo Brady Future Faculty FellowshipUNSPECIFIED
Record Number:CaltechAUTHORS:20180608-085634860
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20180608-085634860
Official Citation:Elucidating Zn and Mg Electrodeposition Mechanisms in Nonaqueous Electrolytes for Next-Generation Metal Batteries. Kim Ta, Kimberly A. See, and Andrew A. Gewirth. The Journal of Physical Chemistry C 2018 122 (25), 13790-13796. DOI: 10.1021/acs.jpcc.8b00835
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86907
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:08 Jun 2018 16:08
Last Modified:05 Jul 2018 18:11

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