Strain-Driven Mn-Reorganization in Overlithiated LixMn2O4 Epitaxial Thin-Film Electrodes

Xiao Chen, Márton Vörös, Juan C. Garcia, Tim T. Fister, D. Bruce Buchholz, Joseph Franklin, Yingge Du, Timothy C. Droubay, Zhenxing Feng, Hakim Iddir, Larry A. Curtiss, Michael J. Bedzyk, Paul Fenter*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

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.

Original languageEnglish (US)
Pages (from-to)2526-2535
Number of pages10
JournalACS Applied Energy Materials
Volume1
Issue number6
DOIs
StatePublished - Jun 25 2018

Keywords

  • X-ray reflectivity
  • lithiation
  • lithium manganese oxide
  • spinel
  • strain

ASJC Scopus subject areas

  • Chemical Engineering (miscellaneous)
  • Energy Engineering and Power Technology
  • Electrochemistry
  • Materials Chemistry
  • Electrical and Electronic Engineering

Fingerprint

Dive into the research topics of 'Strain-Driven Mn-Reorganization in Overlithiated Li<sub>x</sub>Mn<sub>2</sub>O<sub>4</sub> Epitaxial Thin-Film Electrodes'. Together they form a unique fingerprint.

Cite this