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The O2 electrode performance in the Li-O2 battery
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Li-O2 batteries have been attracting increasing attention and R&D efforts as promising power sources for electric vehicles (EVs) due to their significantly higher theoretical energy densities compared to conventional Li-ion batteries. The research presented in this thesis covers the investigation of factors influencing the decomposition of Li2O2, the development of highly active electrocatalysts, and the design of low-cost and easy-operation binder-free O2 electrodes for Li-O2 batteries. Being the main technique, SR-PXD was used both as a continuous light source to advance the electrochemical decomposition of Li2O2 under the X-ray illumination and an operando tool that allowed us to probe the degradation of Li2O2.

Since XRD was intensively used in my thesis work, the effect of X-ray irradiation on the stability of Li2O2 was studied. The accelerating effect of X-rays on the electrochemical decomposition of Li2O2 was, for the first time, explored. The electrochemical decomposition rate of Li2O2 was proportional to the X-ray intensity used. It is proposed that the decomposition might involve a three-step reaction with [Li2O2]x+ and Li2-xO2* as intermediates, which followed pseudo-zero-order kinetics. Then, three electrocatalysts (Pt/MNT, Ru/MNT and Li2C8H2O6) were developed, which exhibited good electrocatalytic performances during the OER. Their activities were evaluated by following the Li2O2 decomposition in electrodes during the charging processes. In addition, the time-resolved OER kinetics for the electrocatalyst-containing Li-O2 cells charged galvanostatically and potentiostatically was systematically investigated using operando SR-PXD. It was found that a small amount of Pt or Ru decoration on the MNTs enhanced the OER efficiency in a Li-O2 cell. The Li2O2 decomposition of an electrode with 5 wt% Pt/MNT, 2 wt% Ru/MNT or Li2C8H2O6 in a Li-O2 cell followed pseudo-zero-order kinetics. Finally, a novel binder-free NCPE for Li-O2 batteries was presented. It displayed a bird’s nest microstructure, which could provide the self-standing electrode with considerable mechanic durability, fast O2 diffusion and enough space for the discharge product deposition. The NCPE contained N-containing functional groups, which may promote the electrochemical reactions.

Place, publisher, year, edition, pages
Uppsala: Uppsala universitet, 2015. , 73 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1271
Keyword [en]
Li-oxygen battery, X-ray irradiation, Electrocatalyst, Synchrotron radiation powder X-ray diffraction, Time-resolved kinetics, Binder-free cathode, Bird’s nest microstructure.
National Category
Inorganic Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-259589ISBN: 978-91-554-9294-6 (print)OAI: oai:DiVA.org:uu-259589DiVA: diva2:844848
Public defence
2015-09-25, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2015-09-03 Created: 2015-08-09 Last updated: 2016-04-21
List of papers
1. Accelerated Electrochemical Decomposition of Li2O2 under X-ray Illumination
Open this publication in new window or tab >>Accelerated Electrochemical Decomposition of Li2O2 under X-ray Illumination
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2013 (English)In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 4, no 23, 4045-4050 p.Article in journal (Refereed) Published
Abstract [en]

This work presents the first report detailing the effect of X-rays on the electrochemical decomposition of Li2O2, which is the main reaction during the charging process in a Li-O-2 battery. An operando synchrotron radiation powder X-ray diffraction (SR-PXD) experiment was performed. The results indicate that the electrochemical decomposition of Li2O2 is dramatically accelerated under X-ray irradiation. The accelerated decomposition of Li2O2 follows a zero-order reaction, and the decomposition rate constant is proportional to the intensity of X-ray used. A mechanism for the electrochemical decomposition of Li2O2 under X-ray irradiation is proposed. These results give an insight into the charging process in Li-O-2 batteries.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-214019 (URN)10.1021/jz402230s (DOI)000328101000005 ()
Available from: 2014-01-07 Created: 2014-01-07 Last updated: 2017-12-06Bibliographically approved
2. Pt/α-MnO2 nanotube: a highly active electrocatalyst for Li-Obattery
Open this publication in new window or tab >>Pt/α-MnO2 nanotube: a highly active electrocatalyst for Li-Obattery
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2014 (English)In: Nano Energy, ISSN 2211-2855, Vol. 10, 19-27 p.Article in journal (Refereed) Published
Abstract [en]

The preparation of α-MnO2 nanotubes (M-NT) decorated with platinum nanoparticles (Pt/M-NT) by a simple reduction and mechanical stirring method is presented in this work, which aims to design a highly active catalyst for the Li-O2 battery. The obtained samples were characterized by XRD, SEM, TEM, BET, and XPS techniques. The electrocatalytic performance of the prepared samples was evaluated by tracking the decomposition of Li2O2 during the charging process in a Li-O2 cell using in situ XRD and operando SR-PXD, which gave direct and time resolved information during the whole process. The results indicated that Pt nanoparticles were uniformly dispersed on the surface of M-NT. Even a small amount (1 wt%) of Pt on M-NT did largely enhance the kinetics of the charging process. A cell with 5 wt% Pt/M-NT showed the highest catalytic activity and lowest charging potential. The decomposition of Li2O2 during the charging process in a Li-O2 cell with 5 wt% Pt/M-NT followed a zero-order reaction. This promoting effect from the supported nanocatalyst can be attributed to the high surface area, highly dispersed and uniform Pt deposition, and proper surface state modifications.

Place, publisher, year, edition, pages
Elsevier, 2014
Keyword
Pt nanoparticle, MnO2 nanotube, Li-O2 battery, charging process, electrocatalysis, operando synchrotron-based XRD
National Category
Materials Chemistry
Research subject
Chemistry with specialization in Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-234462 (URN)10.1016/j.nanoen.2014.08.022 (DOI)000345986500003 ()
Funder
Swedish Research CouncilSwedish Energy Agency
Available from: 2014-10-18 Created: 2014-10-18 Last updated: 2016-04-21Bibliographically approved
3. Ru/α-MnO2 nanotube catalysts for electrochemical decomposition of Li2O2 in Li-O2 batteries
Open this publication in new window or tab >>Ru/α-MnO2 nanotube catalysts for electrochemical decomposition of Li2O2 in Li-O2 batteries
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(English)Manuscript (preprint) (Other academic)
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-259588 (URN)
Available from: 2015-08-09 Created: 2015-08-09 Last updated: 2015-10-13Bibliographically approved
4. An Organic Catalyst for Li-O-2 Batteries: Dilithium Quinone-1,4-Dicarboxylate
Open this publication in new window or tab >>An Organic Catalyst for Li-O-2 Batteries: Dilithium Quinone-1,4-Dicarboxylate
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2015 (English)In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 8, no 13, 2198-2203 p.Article in journal (Refereed) Published
Abstract [en]

Solid organic electrocatalysts have hardly been tested in Li-O-2 batteries. Here, a new solid organic electrocatalyst, dilithium quinone-1,4-dicarboxylate (Li2C8H2O6) is presented, which is expected to overcome the shortcomings of inorganic catalysts. The function-oriented synthesis is low cost and low polluting. The electrocatalytic performance is evaluated by following the degradation of Li2O2 during the charge process in a Li-O-2 cell through insitu XRD and operando synchrotron radiation powder XRD (SR-PXD) measurements. The results indicate that the electrocatalytic activity of Li2C8H2O6 is similar to that of commercial Pt. The Li2O2 decomposition in a cell with Li2C8H2O6 catalyst follows a pseudo-zero-order reaction, virtually without any side reactions. These results provide an insight into the development of new organic catalysts for the oxygen evolution reaction (OER) in Li-O-2 batteries.

Keyword
batteries, energy conversion, kinetics, lithium, x-ray diffraction
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-259650 (URN)10.1002/cssc.201500381 (DOI)000357619000006 ()26073442 (PubMedID)
Funder
Swedish Research CouncilSwedish Energy AgencyÅForsk (Ångpanneföreningen's Foundation for Research and Development)Carl Tryggers foundation
Note

Funding: StandUp for Energy, J. Gust. Richert Foundation , China Scholarship Council

Available from: 2015-08-20 Created: 2015-08-10 Last updated: 2017-12-04Bibliographically approved
5. Binder-free nitrogen-doped carbon paper electrodes derived from polypyrrole/cellulose composite for Li-O2 batteries
Open this publication in new window or tab >>Binder-free nitrogen-doped carbon paper electrodes derived from polypyrrole/cellulose composite for Li-O2 batteries
2016 (English)In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 306, 559-566 p.Article in journal (Refereed) Published
Abstract [en]

This work presents a novel binder-free nitrogen-doped carbon paper electrode (NCPE), which was derived from a N-rich polypyrrole (PPy)/cellulose-chopped carbon filaments (CCFs) composite, for Li–O2 batteries. The fabrication of NCPE involved cheap raw materials (e.g., Cladophora sp. green algae) and easy operation (e.g., doping N by a carbonization of N-rich polymer), which is especially suitable for large-scale production. The NCPE exhibited a bird's nest microstructure, which could provide the self-standing electrode with considerable mechanic durability, fast Li+ and O2 diffusion, and enough space for the discharge product deposition. In addition, the NCPE contained N-containing function groups, which may promote the electrochemical reactions. Furthermore, binder-free architecture designs can prevent binder-involved parasitic reactions. A Li–O2 cell with the NCPE displayed a cyclability of more than 30 cycles at a constant current density of 0.1 mA/cm2. The 1st discharge capacity for a cell with the NCPE reached 8040 mAh/g at a current density of 0.1 mA/cm2, with a cell voltage around 2.81 V. A cell with the NCPE displayed a coulombic efficiency of 81% on the 1st cycle at a current density of 0.2 mA/cm2. These results represent a promising progress in the development of a low-cost and versatile paper-based O2 electrode for Li–O2 batteries.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-259587 (URN)10.1016/j.jpowsour.2015.12.074 (DOI)000370309300069 ()
Funder
Swedish Research Council, 20124681Swedish Energy AgencyÅForsk (Ångpanneföreningen's Foundation for Research and Development)
Available from: 2015-08-09 Created: 2015-08-09 Last updated: 2017-12-04Bibliographically approved

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