---
_id: '9301'
abstract:
- lang: eng
text: Electrodepositing insulating lithium peroxide (Li2O2) is the key process during
discharge of aprotic Li–O2 batteries and determines rate, capacity, and reversibility.
Current understanding states that the partition between surface adsorbed and dissolved
lithium superoxide governs whether Li2O2 grows as a conformal surface film or
larger particles, leading to low or high capacities, respectively. However, better
understanding governing factors for Li2O2 packing density and capacity requires
structural sensitive in situ metrologies. Here, we establish in situ small- and
wide-angle X-ray scattering (SAXS/WAXS) as a suitable method to record the Li2O2
phase evolution with atomic to submicrometer resolution during cycling a custom-built
in situ Li–O2 cell. Combined with sophisticated data analysis, SAXS allows retrieving
rich quantitative structural information from complex multiphase systems. Surprisingly,
we find that features are absent that would point at a Li2O2 surface film formed
via two consecutive electron transfers, even in poorly solvating electrolytes
thought to be prototypical for surface growth. All scattering data can be modeled
by stacks of thin Li2O2 platelets potentially forming large toroidal particles.
Li2O2 solution growth is further justified by rotating ring-disk electrode measurements
and electron microscopy. Higher discharge overpotentials lead to smaller Li2O2
particles, but there is no transition to an electronically passivating, conformal
Li2O2 coating. Hence, mass transport of reactive species rather than electronic
transport through a Li2O2 film limits the discharge capacity. Provided that species
mobilities and carbon surface areas are high, this allows for high discharge capacities
even in weakly solvating electrolytes. The currently accepted Li–O2 reaction mechanism
ought to be reconsidered.
acknowledged_ssus:
- _id: EM-Fac
acknowledgement: S.A.F. and C.P. are indebted to the European Research Council under
the European Union's Horizon 2020 research and innovation program (Grant Agreement
No. 636069), the Austrian Federal Ministry of Science, Research and Economy, and
the Austrian Research Promotion Agency (Grant No. 845364). We acknowledge A. Zankel
and H. Schroettner for support with SEM measurements. C.P. thanks N. Kostoglou,
C. Koczwara, M. Hartmann, and M. Burian for discussions on gas sorption analysis,
C++ programming, Monte Carlo modeling, and in situ SAXS experiments, respectively.
We thank S. Stadlbauer for help with Karl Fischer titration, R. Riccò for gas sorption
measurements, and acknowledge Graz University of Technology for support through
the Lead Project LP-03. Likewise, the use of SOMAPP Lab, a core facility supported
by the Austrian Federal Ministry of Education, Science and Research, the Graz University
of Technology, the University of Graz, and Anton Paar GmbH is acknowledged. S.A.F.
is indebted to Institute of Science and Technology Austria (IST Austria) for support.
This research was supported by the Scientific Service Units of IST Austria through
resources provided by the Electron Microscopy Facility.
article_number: e2021893118
article_processing_charge: No
article_type: original
author:
- first_name: Christian
full_name: Prehal, Christian
last_name: Prehal
- first_name: Aleksej
full_name: Samojlov, Aleksej
last_name: Samojlov
- first_name: Manfred
full_name: Nachtnebel, Manfred
last_name: Nachtnebel
- first_name: Ludek
full_name: Lovicar, Ludek
id: 36DB3A20-F248-11E8-B48F-1D18A9856A87
last_name: Lovicar
orcid: 0000-0001-6206-4200
- first_name: Manfred
full_name: Kriechbaum, Manfred
last_name: Kriechbaum
- first_name: Heinz
full_name: Amenitsch, Heinz
last_name: Amenitsch
- first_name: Stefan Alexander
full_name: Freunberger, Stefan Alexander
id: A8CA28E6-CE23-11E9-AD2D-EC27E6697425
last_name: Freunberger
orcid: 0000-0003-2902-5319
citation:
ama: Prehal C, Samojlov A, Nachtnebel M, et al. In situ small-angle X-ray scattering
reveals solution phase discharge of Li–O2 batteries with weakly solvating electrolytes.
Proceedings of the National Academy of Sciences. 2021;118(14). doi:10.1073/pnas.2021893118
apa: Prehal, C., Samojlov, A., Nachtnebel, M., Lovicar, L., Kriechbaum, M., Amenitsch,
H., & Freunberger, S. A. (2021). In situ small-angle X-ray scattering reveals
solution phase discharge of Li–O2 batteries with weakly solvating electrolytes.
Proceedings of the National Academy of Sciences. National Academy of Sciences.
https://doi.org/10.1073/pnas.2021893118
chicago: Prehal, Christian, Aleksej Samojlov, Manfred Nachtnebel, Ludek Lovicar,
Manfred Kriechbaum, Heinz Amenitsch, and Stefan Alexander Freunberger. “In Situ
Small-Angle X-Ray Scattering Reveals Solution Phase Discharge of Li–O2 Batteries
with Weakly Solvating Electrolytes.” Proceedings of the National Academy of
Sciences. National Academy of Sciences, 2021. https://doi.org/10.1073/pnas.2021893118.
ieee: C. Prehal et al., “In situ small-angle X-ray scattering reveals solution
phase discharge of Li–O2 batteries with weakly solvating electrolytes,” Proceedings
of the National Academy of Sciences, vol. 118, no. 14. National Academy of
Sciences, 2021.
ista: Prehal C, Samojlov A, Nachtnebel M, Lovicar L, Kriechbaum M, Amenitsch H,
Freunberger SA. 2021. In situ small-angle X-ray scattering reveals solution phase
discharge of Li–O2 batteries with weakly solvating electrolytes. Proceedings of
the National Academy of Sciences. 118(14), e2021893118.
mla: Prehal, Christian, et al. “In Situ Small-Angle X-Ray Scattering Reveals Solution
Phase Discharge of Li–O2 Batteries with Weakly Solvating Electrolytes.” Proceedings
of the National Academy of Sciences, vol. 118, no. 14, e2021893118, National
Academy of Sciences, 2021, doi:10.1073/pnas.2021893118.
short: C. Prehal, A. Samojlov, M. Nachtnebel, L. Lovicar, M. Kriechbaum, H. Amenitsch,
S.A. Freunberger, Proceedings of the National Academy of Sciences 118 (2021).
date_created: 2021-03-31T07:00:01Z
date_published: 2021-04-06T00:00:00Z
date_updated: 2023-09-05T13:27:18Z
day: '06'
department:
- _id: StFr
- _id: EM-Fac
doi: 10.1073/pnas.2021893118
external_id:
isi:
- '000637398300050'
intvolume: ' 118'
isi: 1
issue: '14'
keyword:
- small-angle X-ray scattering
- oxygen reduction
- disproportionation
- Li-air battery
language:
- iso: eng
main_file_link:
- open_access: '1'
url: https://doi.org/10.26434/chemrxiv.11447775
month: '04'
oa: 1
oa_version: Preprint
publication: Proceedings of the National Academy of Sciences
publication_identifier:
eissn:
- 1091-6490
issn:
- 0027-8424
publication_status: published
publisher: National Academy of Sciences
quality_controlled: '1'
status: public
title: In situ small-angle X-ray scattering reveals solution phase discharge of Li–O2
batteries with weakly solvating electrolytes
type: journal_article
user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1
volume: 118
year: '2021'
...