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Constraining Si Particles within Graphene Foam Monolith: Interfacial Modification for High-Performance Li+ Storage and Flexible Integrated Configuration
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry. Northwestern Polytech Univ, Sch Mat Sci & Engn, Ctr Nano Energy Mat, State Key Lab Solidifi cation Proc, Xian 710072, Peoples R China..
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
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2016 (English)In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 26, no 37, 6797-6806 p.Article in journal (Refereed) Published
Abstract [en]

Pulverization of electrode materials and loss of electrical contact have been identified as the major causes for the performance deterioration of alloy anodes in Li-ion batteries. This study presents the hierarchical arrangement of spatially confining silicon nanoparticles (Si NPs) within graphene foam (GF) for alleviating these issues. Through a freeze-drying method, the highly oriented GF monolith is engineered to fully encapsulate the Si NPs, serving not only as a robust framework with the well-accessible thoroughfares for electrolyte percolation but also a physical blocking layer to restrain Si from direct exposure to the electrolyte. In return, the pillar effect of Si NPs prevents the graphene sheets from restacking while preserving the highly efficient electron/Li+ transport channels. When evaluated as a binder-free anode, impressive cycle performance is realized in both half-cell and full-cell configurations. Operando X-ray diffraction and in-house X-ray photoelectron spectroscopy confirm the pivotal protection of GF to sheathe the most volume-expanded lithiated phase (Li15Si4) at room temperature. Furthermore, a free-standing composite film is developed through readjusting the pore size in GF/Si monolith and directly integrated with nanocellulose membrane (NCM) separator. Because of the good electrical conductivity and structural integrity of the GF monolith as well as the flexibility of the NCM separator, the as-developed GF/Si-NCM electrode showcases the potential use in the flexible electronic devices.

Place, publisher, year, edition, pages
2016. Vol. 26, no 37, 6797-6806 p.
National Category
Materials Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-306736DOI: 10.1002/adfm.201602324ISI: 000384810300011OAI: oai:DiVA.org:uu-306736DiVA: diva2:1045568
Funder
Swedish Foundation for Strategic Research Swedish Research Council, 2012-4681StandUpSwedish Energy Agency
Available from: 2016-11-10 Created: 2016-11-03 Last updated: 2017-10-06Bibliographically 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. 71 p.
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

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