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Quantifying the capacity contributions during activation of Li2MnO3

DOI: 10.1021/acsenergylett.9b02799 DOI Help

Authors: Jatinkumar Rana (Binghamton University) , Joseph K. Papp (University of California; Lawrence Berkeley National Laboratory) , Zachary Lebens-higgins (Binghamton University) , Mateusz Zuba (Binghamton University) , Lori A. Kaufman (University of California; Lawrence Berkeley National Laboratory) , Anshika Goel (Binghamton University) , Richard Schmuch (Forschungszentrum Juelich GmbH) , Martin Winter (University of Muenster) , M. Stanley Whittingham (Binghamton University) , Wanli Yang (Advanced Light Source) , Bryan D. Mccloskey (University of California; Lawrence Berkeley National Laboratory) , Louis F. J. Piper (Binghamton University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acs Energy Letters

State: Published (Approved)
Published: January 2020
Diamond Proposal Number(s): 22250

Abstract: Though Li2MnO3 was originally considered to be electrochemically inert, its observed activation has spawned a new class of Li-rich layered compounds that deliver capacities beyond the traditional transition-metal redox limit. Despite progress in our understanding of oxygen redox in Li-rich compounds, the underlying origin of the initial charge capacity of Li2MnO3 remains hotly contested. To resolve this issue, we review all possible charge compensation mechanisms including bulk oxygen redox, oxidation of Mn4+, and surface degradation for Li2MnO3 cathodes displaying capacities exceeding 350 mAh g–1. Using elemental and orbital selective X-ray spectroscopy techniques, we rule out oxidation of Mn4+ and bulk oxygen redox during activation of Li2MnO3. Quantitative gas-evolution and titration studies reveal that O2 and CO2 release accounted for a large fraction of the observed capacity during activation with minor contributions from reduced Mn species on the surface. These studies reveal that, although Li2MnO3 is considered critical for promoting bulk anionic redox in Li-rich layered oxides, Li2MnO3 by itself does not exhibit bulk oxygen redox or manganese oxidation beyond its initial Mn4+ valence.

Subject Areas: Chemistry, Energy


Instruments: I09-Surface and Interface Structural Analysis

Other Facilities: Advanced Light Source