High performance pseudo-capacitors based on multicomponent transition metal oxides by local distortion of oxygen octahedra = 다중성분의 전이 금속 산화물에서 산소 팔면체의 국부적 뒤틀림을 이용한 고성능의 슈도커패시터에 관한 연구

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dc.contributor.advisorChoi, Jang Wook-
dc.contributor.advisor최장욱-
dc.contributor.authorLee, Hyeon Jeong-
dc.date.accessioned2019-08-28T02:38:08Z-
dc.date.available2019-08-28T02:38:08Z-
dc.date.issued2016-
dc.identifier.urihttp://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=849856&flag=dissertationen_US
dc.identifier.urihttp://hdl.handle.net/10203/265565-
dc.description학위논문(석사) - 한국과학기술원 : EEWS대학원, 2016.2,[iv, 30 p. :]-
dc.description.abstractVarious metal oxides have been intensively investigated as active materials for pseudo-capacitors, a bridging technology between electric double layer capacitors and rechargeable batteries. A considerable amount of research so far has focused largely on the synthesis of nanostructured metal oxides/chalcogenides and their assembly with conductive nanomaterials even though in-depth understandings regarding crystal chemistry of active materials and suggestions of a new chemical combination are essential steps toward accomplishing higher capacitance. Herein we report that the performance of metal-oxide pseudo-capacitors can be significantly enhanced by engaging MO-type oxides with multiple transition metals: M = Ni, Co, and Mn. According to a series of X-ray absorption near edge spectroscopy (XANES) analyses, the aliovalent states of Co and Mn in contrast to the 2+ state of Ni were identified in the multicomponent TM oxides. In addition, a much wider redox swing of Ni was found as a key feature in the solid-solution oxides. Ab initio density functional theory (DFT) calculations demonstrated that cation vacancies and aliovalent Co and Mn could easily induce permanent local distortions of [$NiO_6$] octahedra. As this type of distortion breaks the degenerate eg level of Ni, the main redox center for pseudo-capacitance, Jahn-Teller lattice instability can be effectively avoided during the $Ni^{2+/3+}$ redox flip, resulting in remarkably enhanced electrochemical capacitance. Our findings highlight the significance of structure?property correlation and further capacitance improvement is also suggested through the optimum control of local distortions.-
dc.languageeng-
dc.publisher한국과학기술원-
dc.subjectDensity functional theory▼ajahn-teller effect▼aoctahedron distortion▼apseudo-capacitors▼asolid-solutions-
dc.subject밀도 함수 이론▼a얀-텔러 효과▼a팔면체 뒤틀림▼a슈도커패시터▼a고용체-
dc.titleHigh performance pseudo-capacitors based on multicomponent transition metal oxides by local distortion of oxygen octahedra = 다중성분의 전이 금속 산화물에서 산소 팔면체의 국부적 뒤틀림을 이용한 고성능의 슈도커패시터에 관한 연구-
dc.typeThesis(Master)-
dc.identifier.CNRN325007-
dc.description.department한국과학기술원 :EEWS대학원,-
dc.contributor.alternativeauthor이현정-
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