In-Situ and First Principles Characterization of Alpha-Manganese Oxide (MnO2)

Abstract

Alpha manganese oxide (α-MnO2) is of interest as a cathode material for lithium-ion batteries and as an electrode/electrocatalyst for hybrid Li-ion/Li-O2 systems. It has a tunnel structure with large 2x2 channels that accommodate different species such as Ba2+, K+, NH4 +, or H3O+/H2O. Characterization and modeling of the insertion and removal of Li, oxygen, and H3O+/H2O species under electrochemical cycling and heating is important for understanding how MnO2 acts as a hybrid Li-ion/Li-O2 battery material. In this talk, we will discuss our work in using in-situ synchrotron X-ray diffraction (XRD), X-ray absorption near-edge spectroscopy (XANES), in-situ UV resonance Raman spectroscopy, and density functional theory (DFT) calculations, to unravel the changes in α-MnO2during electrochemical cycling as well as dehydration process. We found evidence of oxygen incorporation and partial removal during electrochemical cycling, as well as two-stage water removal during heating. Both processes involve facile oxygen diffusion through the center of 2x2 tunnels. Keywords: MnO2, in-situ XRD, DFT Reference: Z.-Z. Yang, D. Ford, J.-S. Park, Y. Ren, S. Kim, H. Kim, T. Fister, M. K. Y. Chan,# M. M. Thackeray,# “Probing the release and uptake of water in α-MnO2•xH2O,” Chemistry of Materials 29, 1507–1517 (2017).Z. Yang, L. Trahey, Y. Ren, M. K. Y. Chan,# C. Lin, J. Okasinski, and M. M. Thackeray, “In-Situ High-Energy Synchrotron X-ray Diffraction Studies and First Principles Modeling of α-MnO2 Electrodes in Li-O2 and Li-ion Coin Cells,” Journal of Materials Chemistry A 3, 7389-7398 (2015). Acknowledgements: This work was supported as a part of the Center for Electrochemical Energy Science, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Basic Energy Sciences under award number DE-AC02–06CH11. Use of the Advanced Photon Source, a US DOE Office of Science User Facility operated by Argonne National Laboratory, was supported by DOE under Contract No. DE-AC02-06CH11357. Use of the Center for Nanoscale Materials, an Office of Science user facility, was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Figure 1