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3-D binder-free graphene foam as cathode for high capacity Li-O2 batteries
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry. (Ångström Advanced Battery Centre)ORCID iD: 0000-0002-8915-3032
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
Stockholm Univ, Dept Mat & Environm Chem, SE-10691 Stockholm, Sweden.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
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2016 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 4, no 25, p. 9767-9773Article in journal (Other (popular science, discussion, etc.)) Published
Abstract [en]

To provide energy densities higher than those of conventional Li-ion batteries, a Li–O2 battery requires a cathode with high surface area to host large amounts of discharge product Li2O2. Therefore, reversible formation of discharge products needs to be investigated in Li–O2 cells containing high surface area cathodes. In this study, a binder-free oxygen electrode consisting of a 3-D graphene structure on aluminum foam, with a high defect level (ID/IG = 1.38), was directly used as the oxygen electrode in Li– O2 batteries, delivering a high capacity of about 9 *104 mA h g-1 (based on the weight of graphene) at the first full discharge using a current density of 100 mA ggraphene-1 . This performance is attributed to the 3-D porous structure of graphene foam providing both an abundance of available space for the deposition of discharge products and a high density of reactive sites for Li–O2 reactions. Furthermore, the formation of discharge products with different morphologies and their decomposition upon charge were observed by SEM. Some nanoscaled LiOH particles embedded in the toroidal Li2O2 were detected by XRD and visualized by TEM. The amount of Li2O2 formed at the end of discharge was revealed by a titration method combined with UV-Vis spectroscopy analysis. 

Place, publisher, year, edition, pages
2016. Vol. 4, no 25, p. 9767-9773
National Category
Materials Chemistry
Research subject
Chemistry with specialization in Materials Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-291383DOI: 10.1039/C5TA10690GISI: 000378716900008OAI: oai:DiVA.org:uu-291383DiVA, id: diva2:925439
Conference
Inorganic Days, Visby, June 15 - 17, 2015
Projects
Swedish Research CouncilSwedish Energy AgencyÅngpanneföreningen’s Foundation for Research and DevelopmentJ. Gust. Richert FoundationState Key Laboratory of Fine Chemicals (KF1413)China Scholarship Council
Funder
Swedish Research Council, 2012-4681; 2011-6512Swedish Energy AgencyÅForsk (Ångpanneföreningen's Foundation for Research and Development)
Available from: 2016-05-02 Created: 2016-05-02 Last updated: 2018-01-03Bibliographically approved
In thesis
1. Exploration of Non-Aqueous Metal-O2 Batteries via In Operando X-ray Diffraction
Open this publication in new window or tab >>Exploration of Non-Aqueous Metal-O2 Batteries via In Operando X-ray Diffraction
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Non-aqueous metal-air (Li-O2 and Na-O2) batteries have been emerging as one of the most promising high-energy storage systems to meet the requirements for demanding applications due to their high theoretical specific energy. In the present thesis work, advanced characterization techniques are demonstrated for the exploration of metal-O2 batteries. Prominently, the electrochemical reactions occurring within the Li-O2 and Na-O2 batteries upon cycling are studied by in operando powder X-ray diffraction (XRD).

In the first part, a new in operando cell with a combined form of coin cell and pouch cell is designed. In operando synchrotron radiation powder X-ray diffraction (SR-PXD) is applied to investigate the evolution of Li2O2 inside the Li-O2 cells with carbon and Ru-TiC cathodes. By quantitatively tracking the Li2O2 evolution, a two-step process during growth and oxidation is observed.

This newly developed analysis technique is further applied to the Na-O2 battery system. The formation of NaO2 and the influence of the electrolyte salt are followed quantitatively by in operando SR-PXD. The results indicate that the discharge capacity of Na-O2 cells containing a weak solvating ether solvent depends heavily on the choice of the conducting salt anion, which also has impact on the growth of NaO2 particles.

In addition, the stability of the discharge product in Na-O2 cells is studied. Using both ex situ and in operando XRD, the influence of sodium anode, solvent, salt and oxygen on the stability of NaO2 are quantitatively identified. These findings bring new insights into the understanding of conflicting observations of different discharge products in previous studies.

In the last part, a binder-free graphene based cathode concept is developed for Li-O2 cells. The formation of discharge products and their decomposition upon charge, as well as different morphologies of the discharge products on the electrode, are demonstrated. Moreover, considering the instability of carbon based cathode materials, a new type of titanium carbide on carbon cloth cathode is designed and fabricated. With a surface modification by loading Ru nanoparticles, the titanium carbide shows enhanced oxygen reduction/evolution activity and stability. Compared with the carbon based cathode materials, titanium carbide demonstrated a higher discharge and charge efficiency.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. p. 71
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1572
Keyword
Keywords: lithium-oxygen batteries, sodium-oxygen batteries, metal-air, in operando X-ray diffraction, cathode materials
National Category
Materials Chemistry
Research subject
Chemistry with specialization in Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-330889 (URN)978-91-513-0094-8 (ISBN)
Public defence
2017-11-24, ITC 1211, Lägerhyddsvägen 2, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2017-11-02 Created: 2017-10-06 Last updated: 2017-11-02
2. Li2O2 quantification in non-aqueous Li-O2 batteries with binder-free cathodes
Open this publication in new window or tab >>Li2O2 quantification in non-aqueous Li-O2 batteries with binder-free cathodes
2017 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The non-aqueous Li-air (Li-O2) battery has been emerging as one of the most promising high-energy storage systems to meet the requirements for electric vehicle applications due to its high theoretical energy density. In order to uncover the underlying electrochemistry and enable an informed battery design, it is crucial to gain a detailed understanding of the cell´s chemical components as well as its behavior during cycling.

    These two fundamental tasks are reflected in this thesis’ structure: First, advanced characterization techniques are demonstrated in the search for a novel cathode material for Li-O2 batteries. Second, the electrochemical reactions occurring within the battery upon cycling are studied by in operando powder X-ray diffraction.

    In the first part, a novel free-standing oxygen cathode was prepared by a facile and efficient solution-process followed by a low-temperature exfoliation, which displayed a 3-D structure arrangement of graphene foam (GF) derived from a graphene oxide (GO) gel on an aluminum substrate (GF@Al). The as prepared GF@Al was directly used as cathode in Li-O2 batteries without any binder and catalyst, delivering a high capacity about 9×104 mA h·g-1 (based on the weight of graphene) or about 60 mAh·g-1 (based on the weight of the whole electrode) at the first discharge with a current density of 100 mA·ggraphene-1. Furthermore, electrodes have been investigated by X-ray diffraction (XRD), Fourier-transform infrared reflection (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV-Vis spectroscopy titration. The formation of a discharge product and its decomposition upon charge as well as different morphologies of discharge products on the electrode were observed by SEM and TEM.

    In the second part, the evolution of Li2O2 was investigated by synchrotron radiation powder X-ray diffraction (SR-PXD). By quantitatively tracking Li2O2 under the actual electrochemical conditions, a two-step process during growth and oxidation is observed for Li2O2. This is due to different evolution steps during the two stages of both oxygen reduction reactions (ORR) and oxygen evolution reactions (OER). By analyzing the anisotropic broadening of Li2O2 X-ray diffraction peaks, anisotropic disc-like Li2O2 grains were found to be formed rapidly in the first step of discharge, followed by a nucleation and growth of toroidal Li2O2 particles with a LiO2-like surface. During the charging process, Li2O2 was oxidized from the surface first, followed by an oxidation process with a higher decomposition rate for the bulk. This new analysis technique brings additional information on the evolution of Li2O2 in Li-O2 batteries.

Place, publisher, year, edition, pages
Uppsala universitet, 2017
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-337652 (URN)
Opponent
Supervisors
Available from: 2018-01-03 Created: 2018-01-03 Last updated: 2018-01-03Bibliographically approved

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