@article{17b0fc2df00c4aca9ea5852a1696413f,
title = "Strain-Driven Mn-Reorganization in Overlithiated LixMn2O4 Epitaxial Thin-Film Electrodes",
abstract = "Lithium manganate LixMn2O4 (LMO) is a lithium ion cathode that suffers from the widely observed but poorly understood phenomenon of capacity loss due to Mn dissolution during electrochemical cycling. Here, operando X-ray reflectivity (low- and high-angle) is used to study the structure and morphology of epitaxial LMO (111) thin film cathodes undergoing lithium insertion and extraction to understand the inter-relationships between biaxial strain and Mn-dissolution. The initially strain-relieved LiMn2O4 films generate in-plane tensile and compressive strains for delithiated (x < 1) and overlithiated (x > 1) charge states, respectively. The results reveal reversible Li insertion into LMO with no measurable Mn-loss for 0 < x < 1, as expected. In contrast, deeper discharge (x > 1) reveals Mn loss from LMO along with dramatic changes in the intensity of the (111) Bragg peak that cannot be explained by Li stoichiometry. These results reveal a partially reversible site reorganization of Mn ions within the LMO film that is not seen in bulk reactions and indicates a transition in Mn-layer stoichiometry from 3:1 to 2:2 in alternating cation planes. Density functional theory calculations confirm that compressive strains (at x = 2) stabilize LMO structures with 2:2 Mn site distributions, therefore providing new insights into the role of lattice strain in the stability of LMO.",
keywords = "X-ray reflectivity, lithiation, lithium manganese oxide, spinel, strain",
author = "Xiao Chen and M{\'a}rton V{\"o}r{\"o}s and Garcia, {Juan C.} and Fister, {Tim T.} and Buchholz, {D. Bruce} and Joseph Franklin and Yingge Du and Droubay, {Timothy C.} and Zhenxing Feng and Hakim Iddir and Curtiss, {Larry A.} and Bedzyk, {Michael J.} and Paul Fenter",
note = "Funding Information: This research was primarily supported by the Center for Electrochemical Energy Science, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Basic Energy Sciences through Argonne National Laboratory. Argonne is a U.S. Department of Energy laboratory managed by UChicago Argonne, LLC, under contract DE-AC02-06CH11357. Research at the Advanced Photon Source (Station 33BM-C, 12ID-D) at Argonne National Laboratory was also supported by DOE. Computer time allocations at the Argonne{\textquoteright}s Laboratory Computing Resource Center, and the National Energy Research Scientific Computing Center (NERSC, supported by the Office of Science of the U.S. Department of Energy under Contract no. DE-AC02-05CH11231) are gratefully acknowledged. M.V. was supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-06CH11357 (Argonne Research Scholar). D.B.B acknowledges the Pulsed Laser Deposition Shared Facility at the Materials Research Center at Northwestern University that is supported, in part, by the CEES-EFRC program, as well as by the National Science Foundation MRSEC program (DMR-1720139) and the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205). One sample in these studies was made by Y.D., who is funded by the DOE Early Career Research Program for the support on thin film growth performed at the W. R. Wiley Environmental Molecular Sciences Laboratory, a DOE User Facility sponsored by the Office of Biological and Environmental Research. J.F. acknowledges support from the European Union Horizon 2020 under the Marie Sklodowska-Curie grant agreement No. 705339 and is grateful for support from the Science and Technology Facilities Council Early Career award, ST/K00171X/1. Dr. Javier edged for helpful discussions. Publisher Copyright: {\textcopyright} 2018 American Chemical Society.",
year = "2018",
month = jun,
day = "25",
doi = "10.1021/acsaem.8b00270",
language = "English (US)",
volume = "1",
pages = "2526--2535",
journal = "ACS Applied Energy Materials",
issn = "2574-0962",
publisher = "American Chemical Society",
number = "6",
}