Direct observation of MgO formation at cathode electrolyte interface of a spinel MgCo₂O₄ cathode upon electrochemical Mg removal and insertion

Journal Article · Sat Jun 01 00:00:00 EDT 2019 · Journal of Power Sources

DOI:https://doi.org/10.1016/j.jpowsour.2019.03.102· OSTI ID:1524066

Sa, Niya ^[1]; Mukherjee, Arijita ^[2]; Han, Binghong  ^[3]; Ren, Yang ^[4]; Klie, Robert F. ^[2]; Key, Baris ^[5]; Vaughey, John T. ^[5]

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1. Univ. of Massachusetts, Boston, MA (United States); Argonne National Lab. (ANL), Argonne, IL (United States). Joint Center for Energy Storage Research (JCESR); Argonne National Lab. (ANL), Argonne, IL (United States). Chemical Sciences and Engineering Division
2. Argonne National Lab. (ANL), Argonne, IL (United States). Joint Center for Energy Storage Research (JCESR); Univ. of Illinois, Chicago, IL (United States). Dept. of Physics
3. Argonne National Lab. (ANL), Argonne, IL (United States). Chemical Sciences and Engineering Division
4. Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
5. Argonne National Lab. (ANL), Argonne, IL (United States). Joint Center for Energy Storage Research (JCESR); Argonne National Lab. (ANL), Argonne, IL (United States). Chemical Sciences and Engineering Division

Identifying a Mg²⁺ insertion mechanism into Mg cathode is one crucial challenge of designing Mg batteries that own comparable specific energy to the lithium ion systems. Spinel Mg cathodes are attractive candidates mainly attributed to its high intercalation voltage and theoretical capacity, however, electrochemically removing Mg from its solid structure with identified capacity dedicated to actual reversible Mg intercalation introduce complications. Work presented here applies Scanning/Transmission Electron Microscopy with Energy Loss Spectroscopy and diffraction method to investigate the cathode electrolyte interface for a spinel MgCo₂O₄ material electrochemically cycled in the presence of a non-aqueous, low water content Mg electrolyte. Findings at an atomic scale suggest a complete de-magnesiation is occurring for thin MgCo₂O₄ particles upon electrochemical charging, but a vast majority of MgCo₂O₄ shows formation of an amorphous MgO layer with a thickness of similar to ~10 nm at the cathode electrolyte interface. The amorphous MgO layer is directly jointed with the crystalline MgCo₂O₄ at the outer edge of the cathode. Formation of MgO at the cathode electrolyte interface is believed to be the detrimental factor preventing further electrochemical cell cycling of MgCo₂O₄. A possible reaction pathway of intercalation-initiated surface conversion is proposed to explain reversible Mg insertion with MgCo₂O₄.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1524066
• Alternate ID(s): OSTI ID: 1547571
• Journal Information: Journal of Power Sources, Vol. 424, Issue C; ISSN 0378-7753
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

25 ENERGY STORAGE
magnesium
spinel
cathode
STEM