Strain-Driven Mn-Reorganization in Overlithiated LixMn2O4 Epitaxial Thin-Film Electrodes
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- Argonne National Lab. (ANL), Lemont, IL (United States); Northwestern Univ., Evanston, IL (United States)
- Argonne National Lab. (ANL), Lemont, IL (United States)
- Northwestern Univ., Evanston, IL (United States)
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. College London, London (United Kingdom)
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Oregon State Univ., Corvallis, OR (United States)
Here, 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 ithin the LMO film that is not seen in bulk reactions and indicates a transition in Mn-layer toichiometry 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.
- Research Organization:
- Energy Frontier Research Centers (EFRC) (United States). Center for Electrical Energy Storage (CEES); Argonne National Lab. (ANL), Argonne, IL (United States); Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- AC02-06CH11357; AC05-76RL01830
- OSTI ID:
- 1473685
- Alternate ID(s):
- OSTI ID: 1843219
- Report Number(s):
- PNNL-SA-132780; 143605
- Journal Information:
- ACS Applied Energy Materials, Vol. 1, Issue 6; ISSN 2574-0962
- Publisher:
- American Chemical Society (ACS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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