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Effect of the Electrolyte Solvent on Redox Processes in Mg–S Batteries

Bevilacqua, Sarah C. and Pham, Kim H. and See, Kimberly A. (2019) Effect of the Electrolyte Solvent on Redox Processes in Mg–S Batteries. Inorganic Chemistry, 58 (16). pp. 10472-10482. ISSN 0020-1669. doi:10.1021/acs.inorgchem.9b00891.

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Mg–S batteries are attractive for next-generation energy storage because of their high theoretical capacity and low cost. The foremost challenge in Mg–S batteries is designing electrolytes that support reversible electrochemistry at both electrodes. Here, we target a solution-mediated reduction pathway for the S_8 cathode by tailoring the electrolyte solvent. Varying the solvent in Mg-based systems is complicated because of the active nature of the solvent in solvating Mg^(2+) and the complex dynamics of electrolyte–Mg interfaces. To understand the effect of the solvent on the S_8 reduction processes in the Mg–S cell, the magnesium–aluminum chloride complex (MACC) electrolyte was prepared in different ethereal solvents. Reversible Mg electrodeposition is demonstrated in the MACC electrolyte in several solvent systems. The electrodeposition overpotentials and current densities are found to vary with the solvent, suggesting that the solvent plays a noninnocent role in the electrochemical processes at the Mg interface. Mg–S cells are prepared with the electrolytes to understand how the solvent affects the reduction of S_8. A reductive wave is present in all linear-sweep voltammograms, and the peak potential varies with the solvent. The peak potential is approximately 0.8 V versus Mg/Mg^(2+), lower than the expected reduction potential of 1.7 V. We rule out passivation of the Mg anode as the cause for the low voltage peak potential, making processes at the S8 cathode the likely culprit. The ability to oxidize MgS with the MACC electrolyte is also examined, and we find that the oxidation current can be attributed to side reactions at the C–electrolyte interface.

Item Type:Article
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URLURL TypeDescription
Bevilacqua, Sarah C.0000-0002-6834-7145
See, Kimberly A.0000-0002-0133-9693
Additional Information:© 2019 American Chemical Society. Received: March 27, 2019; Published: June 14, 2019. Financial support from Caltech and the Dow Next Generation Educator Fund is gratefully acknowledged. S.C.B. acknowledges the Resnick Sustainability Institute at Caltech for fellowship support. K.H.P. acknowledges funding from the Johnson & Johnson WAVE program at Caltech. The authors thank Charles J. Hansen and Dr. Andrew J. Martinolich for assistance in preparing MgS. The authors thank Dr. David Vander Velde for assistance in the collection of NMR spectra. NMR spectra were obtained on a spectrometer supported by the NIH (Grant RR027690).
Group:Resnick Sustainability Institute
Funding AgencyGrant Number
Dow Next Generation Educator FundUNSPECIFIED
Resnick Sustainability InstituteUNSPECIFIED
Johnson and JohnsonUNSPECIFIED
Issue or Number:16
Record Number:CaltechAUTHORS:20190614-153313156
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Official Citation:Effect of the Electrolyte Solvent on Redox Processes in Mg–S Batteries. Sarah C. Bevilacqua, Kim H. Pham, and Kimberly A. See. Inorganic Chemistry 2019 58 (16), 10472-10482. DOI: 10.1021/acs.inorgchem.9b00891
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:96453
Deposited By: George Porter
Deposited On:17 Jun 2019 14:27
Last Modified:16 Nov 2021 17:21

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