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Effect of Concentration on the Electrochemistry and Speciation of the Magnesium Aluminum Chloride Complex Electrolyte Solution

See, Kimberly A. and Liu, Yao-Min and Ha, Yeyoung and Barile, Christopher J. and Gewirth, Andrew A. (2017) Effect of Concentration on the Electrochemistry and Speciation of the Magnesium Aluminum Chloride Complex Electrolyte Solution. ACS Applied Materials & Interfaces, 9 (41). pp. 35729-35739. ISSN 1944-8244. https://resolver.caltech.edu/CaltechAUTHORS:20180608-090529324

[img] PDF (CV of the 5× MACC electrolyte up to 3.4 V, Tafel analysis of CVs obtained with a macroelectrode, CVs of Cu electrodeposition and stripping, simulated Raman spectra of the monomeric Mg complexes, table with Lorentzian fit values of 35Cl NMR data, sonic...) - Supplemental Material
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Abstract

Magnesium batteries offer an opportunity to use naturally abundant Mg and achieve large volumetric capacities reaching over four times that of conventional Li-based intercalation anodes. High volumetric capacity is enabled by the use of a Mg metal anode in which charge is stored via electrodeposition and stripping processes, however, electrolytes that support efficient Mg electrodeposition and stripping are few and are often prepared from highly reactive compounds. One interesting electrolyte solution that supports Mg deposition and stripping without the use of highly reactive reagents is the magnesium aluminum chloride complex (MACC) electrolyte. The MACC exhibits high Coulombic efficiencies and low deposition overpotentials following an electrolytic conditioning protocol that stabilizes species necessary for such behavior. Here, we discuss the effect of the MgCl_2 and AlCl_3 concentrations on the deposition overpotential, current density, and the conditioning process. Higher concentrations of MACC exhibit enhanced Mg electrodeposition current density and much faster conditioning. An increase in the salt concentrations causes a shift in the complex equilibria involving both cations. The conditioning process is strongly dependent on the concentration suggesting that the electrolyte is activated through a change in speciation of electrolyte complexes and is not simply due to the annihilation of electrolyte impurities. Additionally, the presence of the [Mg_2(μ-Cl)_3·6THF]^+ in the electrolyte solution is again confirmed through careful analysis of experimental Raman spectra coupled with simulation and direct observation of the complex in sonic spray ionization mass spectrometry. Importantly, we suggest that the ∼210 cm^(–1) mode commonly observed in the Raman spectra of many Mg electrolytes is indicative of the C_(3v) symmetric [Mg_2(μ-Cl)_3·6THF]^+. The 210 cm^(–1) mode is present in many electrolytes containing MgCl_2, so its assignment is of broad interest to the Mg electrolyte community.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1021/acsami.7b08088DOIArticle
https://pubs.acs.org/doi/suppl/10.1021/acsami.7b08088PublisherSupporting Information
ORCID:
AuthorORCID
See, Kimberly A.0000-0002-0133-9693
Gewirth, Andrew A.0000-0003-4400-9907
Additional Information:© 2017 American Chemical Society. Received: June 6, 2017; Accepted: September 21, 2017; Published: September 21, 2017. This work was partially supported by the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. K.A.S. acknowledges postdoctoral funding from the St. Elmo Brady Future Faculty Postdoctoral Fellowship. Y.-M.L. acknowledges access to the Orbitrap-MS in the Mass Spectrometry Laboratory at UIUC. C.J.B. acknowledges funding from the National Science Foundation Graduate Research Fellowship (No. NSF DGE-11444245) and a Springborn Fellowship. The authors thank Dr. Taras Pogorelov and Mike Hallock for assistance with Gaussian calculations. The authors declare no competing financial interest.
Funders:
Funding AgencyGrant Number
Department of Energy (DOE)UNSPECIFIED
St. Elmo Brady Future Faculty FellowshipUNSPECIFIED
NSF Graduate Research FellowshipDGE-11444245
Springborn FellowshipUNSPECIFIED
Subject Keywords:magnesium aluminum chloride complex, magnesium battery electrolyte, magnesium deposition, Mg dimer, electrolyte conditioning
Issue or Number:41
Record Number:CaltechAUTHORS:20180608-090529324
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20180608-090529324
Official Citation:Effect of Concentration on the Electrochemistry and Speciation of the Magnesium Aluminum Chloride Complex Electrolyte Solution. Kimberly A. See, Yao-Min Liu, Yeyoung Ha, Christopher J. Barile, and Andrew A. Gewirth. ACS Applied Materials & Interfaces 2017 9 (41), 35729-35739 DOI: 10.1021/acsami.7b08088
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86908
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:08 Jun 2018 16:26
Last Modified:03 Oct 2019 19:49

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