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Nanosized LiFePO4-decorated emulsion-templated carbon foam for 3D micro batteries: a study of structure and electrochemical performance
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.ORCID iD: 0000-0001-5861-4281
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
Stockholm University. (Materials and Environmental Chemistry- Arrhenius laboratory)
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry. DTU.ORCID iD: 0000-0003-2538-8104
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2014 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 6, no 15, 8804-8813 p.Article in journal (Refereed) Published
Abstract [en]

In this article, we report a novel 3D composite cathode fabricated from LiFePO4 nanoparticles deposited conformally on emulsion-templated carbon foam by a sol–gel method. The carbon foam is synthesized via a facile and scalable method which involves the carbonization of a high internal phase emulsion (polyHIPE) polymer template. Various techniques (XRD, SEM, TEM and electrochemical methods) are used to fully characterize the porous electrode and confirm the distribution and morphology of the cathode active material. The major benefits of the carbon foam used in our work are closely connected with its high surface area and the plenty of space suitable for sequential coating with battery components. After coating with a cathode material (LiFePO4nanoparticles), the 3D electrode presents a hierarchically structured electrode in which a porous layer of the cathode material is deposited on the rigid and bicontinuous carbon foam. The composite electrodes exhibit impressive cyclability and rate performance at different current densities affirming their importance as viable power sources in miniature devices. Footprint area capacities of 1.72 mA h cm−2 at 0.1 mA cm−2 (lowest rate) and 1.1 mA h cm−2 at 6 mA cm−2(highest rate) are obtained when the cells are cycled in the range 2.8 to 4.0 V vs. lithium.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2014. Vol. 6, no 15, 8804-8813 p.
National Category
Physical Chemistry Polymer Chemistry Materials Chemistry Inorganic Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-228630DOI: 10.1039/C4NR01682CISI: 000339861500051OAI: oai:DiVA.org:uu-228630DiVA: diva2:734615
Projects
STEM-VR-Microbattery
Available from: 2014-07-18 Created: 2014-07-18 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Multifunctional Carbon Foams by Emulsion Templating: Synthesis, Microstructure, and 3D Li-ion Microbatteries
Open this publication in new window or tab >>Multifunctional Carbon Foams by Emulsion Templating: Synthesis, Microstructure, and 3D Li-ion Microbatteries
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Carbon foams are among the existing electrode designs proposed for use in 3D Li-ion microbatteries. For such electrodes to find applications in practical microbatteries, however, their void sizes, specific surface areas and pore volumes need be optimized. This thesis concerns the synthesis of highly porous carbon foams and their multifunctional applications in 3D microbatteries. The carbon foams are derived from polymers that are obtained by polymerizing high internal phase water-in-oil emulsions (HIPEs).

In general, the carbonization of the sulfonated polymers yielded hierarchically porous structures with void sizes ranging from 2 to 35 µm and a BET specific surface area as high as 630 m2 g-1. Thermogravimetric and spectroscopic evidence indicated that the sulfonic acid groups, introduced during sulfonation, transformed above 250 oC to thioether (-C-S-) crosslinks which were responsible for the thermal stability and charring tendency of the polymer precursors. Depending on the preparation of the HIPEs, the specific surface areas and void-size distributions were observed to vary considerably. In addition, the pyrolysis temperature could also affect the microstructures, the degree of graphitization, and the surface chemistry of the carbon foams.

Various potential applications were explored for the bespoke carbon foams. First, their use as freestanding active materials in 3D microbatteries was studied. The carbon foams obtained at 700 to 1500 oC suffered from significant irreversible capacity loss during the initial discharge. In an effort to alleviate this drawback, the pyrolysis temperature was raised to 2200 oC. The resulting carbon foams were observed to deliver high, stable areal capacities over several cycles. Secondly, the possibility of using these structures as 3D current collectors for various active materials was investigated in-depth. As a proof-of-concept demonstration, positive active materials like polyaniline and LiFePO4 were deposited on the 3D architectures by means of electrodeposition and sol-gel approach, respectively. In both cases, the composite electrodes exhibited reasonably high cyclability and rate performance at different current densities. The syntheses of niobium and molybdenum oxides and their potential application as electrodes in microbatteries were also studied. In such applications, the carbon foams served dual purposes as 3D scaffolds and as reducing reactants in the carbothermal reduction process. Finally, a facile method of coating carbon substrates with oxide nanosheets was developed. The approach involved the exfoliation of crystalline VO2 to prepare dispersions of hydrated V2O5, which were subsequently cast onto CNT paper to form oxide films of different thicknesses.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 139 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1469
Keyword
Battery, Carbon, Electrochemical, Electrodeposition, Emulsion, Energy, Exfoliation, Foam, Lithium, Microbattery, Multifunctional, Nanoparticles, Polyaniline, Polymer, Power, Sol-gel, Storage, Structured, Three-dimensional
National Category
Materials Chemistry Composite Science and Engineering Polymer Technologies Inorganic Chemistry Physical Chemistry Polymer Chemistry Condensed Matter Physics
Research subject
Chemistry with specialization in Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-312897 (URN)978-91-554-9799-6 (ISBN)
Public defence
2017-03-03, Polhemsalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Funder
Swedish Research Council, 2012–4681Swedish Energy Agency
Available from: 2017-02-08 Created: 2017-01-14 Last updated: 2017-02-15

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Publisher's full texthttp://pubs.rsc.org/en/content/articlehtml/2014/nr/c4nr01682c

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Asfaw, Habtom DestaYounesi, RezaValvo, MarioNyholm, LeifEdström, Kristina

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