Abstract

The Ca²⁺ solvation structure at the electrolyte/electrode interface is of central importance to understand electroreduction stability and solid–electrolyte interphase (SEI) formation for the novel multivalent Ca battery systems. Here, using an exemplar electrolyte, the concentration-dependent solvation structure of Ca(BH₄)₂-tetrahydrofuran on a gold model electrode has been investigated with various electrolyte concentrations via electrochemical quartz crystal microbalance with dissipation (EQCM-D) and X-ray photoelectron spectroscopy (XPS). For the first time, in situ EQCM-D results prove that the prevalent species adsorbed at the interface is CaBH₄⁺ across all concentrations. As the salt concentration increases, the number of BH₄^– anions associated with Ca²⁺ increases, and much larger solvated complexes such as CaBH₄⁺·4THF or Ca(BH₄)₃^–·4THF form at the interface at high concentrations prior to Ca plating. Different interfacial chemistries lead to the formation of SEIs with different components demonstrated by XPS. High electrolyte concentrations reduce the solvent decomposition and promote the formation of thick, uniform, and inorganic-rich (i.e., CaO) SEI layers, which contribute to improved Ca plating efficiency and current density in electrochemical measurements.

Authors:

Yang, Zhenzhen  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-1073-3799"

Leon, Noel J. ^[1]; Liao, Chen  ^[1];

• Search DOE PAGES for author "Liao, Chen"
• Search DOE PAGES for ORCID "0000-0001-5168-6493"

Ingram, Brian J.  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-5219-7517"

Trahey, Lynn ^[2]

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+ Show Author Affiliations

1. Argonne National Laboratory (ANL), Argonne, IL (United States). Chemical Sciences and Engineering Division; Argonne National Laboratory (ANL), Argonne, IL (United States). Joint Center for Energy Storage Research (JCESR)
2. Argonne National Laboratory (ANL), Argonne, IL (United States). Joint Center for Energy Storage Research (JCESR)

Publication Date:

Fri May 12 00:00:00 EDT 2023

Research Org.:

Argonne National Laboratory (ANL), Argonne, IL (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1989124

Grant/Contract Number:  

AC02-06CH11357

Resource Type:

Accepted Manuscript

Journal Name:

ACS Applied Materials and Interfaces

Additional Journal Information:

Journal Volume: 15; Journal Issue: 20; Journal ID: ISSN 1944-8244

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Ca(BH4)(2); THF; electrode-electrolyte interface; solvation; in situ EQCM-D; SEI; deposition; electrodes; electrolytes; salts; surface chemistry