Chen, X;
Vörös, M;
Garcia, JC;
Fister, TT;
Buchholz, DB;
Franklin, J;
Du, Y;
... Fenter, P; + view all
(2018)
Strain-Driven Mn-Reorganization in Overlithiated LixMn2O4 Epitaxial Thin-Film Electrodes.
ACS Applied Energy Materials
, 1
(6)
pp. 2526-2535.
10.1021/acsaem.8b00270.
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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.
| Type: | Article |
|---|---|
| Title: | Strain-Driven Mn-Reorganization in Overlithiated LixMn2O4 Epitaxial Thin-Film Electrodes |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1021/acsaem.8b00270 |
| Publisher version: | https://doi.org/10.1016/j.bbalip.2019.05.015 |
| Language: | English |
| Additional information: | This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Chemical Engineering |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10086091 |
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