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dc.contributor.advisorYılmaz, Edaen_US
dc.contributor.authorOkur, Faruken_US
dc.date.accessioned2016-11-22T05:57:11Z
dc.date.available2016-11-22T05:57:11Z
dc.date.copyright2016-10
dc.date.issued2016-11
dc.date.submitted2016-11-18
dc.identifier.urihttp://hdl.handle.net/11693/32539
dc.descriptionCataloged from PDF version of article.en_US
dc.descriptionThesis (M.S.): Bilkent University, Department of Materials Science and Nanotechnology, İhsan Doğramacı Bilkent University, 2016.en_US
dc.descriptionIncludes bibliographical references (leaves 61-72).en_US
dc.description.abstractFossil fuels hold the biggest share in energy sources for a very long time, especially in transportation, because of their appealing properties like very high energy efficiency, easy transport to any place in the world, very straightforward usage principle and they used to be quite abundant. However fossil fuel consumption results into release of harmful greenhouse gasses that causes global warming. On the other hand fossil fuels are not very abundant anymore and as a product that is formed in millions of years, the increasing energy demand worsens the situation. That is why renewable energy sources are more and more pronounced each day in the last half century. Nonetheless, irregular nature of the renewable energy sources makes them highly unpractical. Energy can only be harvested from renewable energy sources in specific time or specific locations, for instance, it is not possible to harvest energy from sun all day long or wind turbines can only be efficient in the places that there is sufficient wind power. This being the case, a clever approach is needed in order to be able to benefit from such convenient energy sources. Energy storage systems are the saviour in this picture since they can be used to store the energy that is produced from renewable energy sources and available when needed. For instance, lithium oxygen (Li-O2) batteries are a very promising candidates for a replacement of fossil fuels in transportation due to their very high theoretical gravimetric energy density. Oxygen is used as active cathode material unwanted side product formations on cathode-electrolyte interface. These side products are accumulating on the cathode surface upon battery cycling and result into drastic capacity fading. Especially carbon based materials are not stable against battery cycling in Li-O2 batteries even tough they have quite profitable features as a cathode material for Li-O2 batteries, such as; high surface area, low weight, high electrical conductivity, good oxygen reduction reaction activity etc. In this thesis study, the motivation is to increase the stability of carbon nanotubes (CNTs) while benefiting from their aforementioned advantages in Li-O2 batteries. In order to achieve this, an ultrathin and uniform titanium dioxide (TiO2) layer is coated on CNT surface by atomic layer deposition method. Prior to TiO2 coating an effective functionalization method is introduced to CNT surfaces to facilitate a uniform coating. Transmission electron microscopy imaging and x-ray diffractometer analysis are performed to observe coating properties. Xray photoelectron spectroscopy analysis and scanning electron microscopy imaging show the subsided side reactions, proving the stability of the TiO2 coated CNT cathode. TiO2 protective layer significantly prevents side product formation due to reduced cathode degradation and shows superior capacity retention compared to pristine CNT cathode upon full capacity battery cycling.en_US
dc.description.statementofresponsibilityby Faruk Okur.en_US
dc.format.extentxiv, 72 pages : illustrations (some color), charts.en_US
dc.language.isoEnglishen_US
dc.rightsinfo:eu-repo/semantics/openAccessen_US
dc.subjectLithium-oxygen batteryen_US
dc.subjectElectrochemical energy storageen_US
dc.subjectNon-carbon interfaceen_US
dc.subjectAtomic layer depositionen_US
dc.subjectTiO2 coatingen_US
dc.subjectMultiwalled carbon nanotubesen_US
dc.titleUltrathin titanium dioxide coatings on carbon nanotubes for stable lithium oxygen battery cathodesen_US
dc.title.alternativeUltra ince titanyum dioksit kaplı dayanıklı lityum oksijen pili katotuen_US
dc.typeThesisen_US
dc.departmentGraduate Program in Materials Science and Nanotechnologyen_US
dc.publisherBilkent Universityen_US
dc.description.degreeM.S.en_US
dc.identifier.itemidB121417
dc.embargo.release2018-11-17


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