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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Various 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.
Advisors
Choi, Jang Wookresearcher최장욱researcher
Description
한국과학기술원 :EEWS대학원,
Publisher
한국과학기술원
Issue Date
2016
Identifier
325007
Language
eng
Description

학위논문(석사) - 한국과학기술원 : EEWS대학원, 2016.2,[iv, 30 p. :]

Keywords

Density functional theory▼ajahn-teller effect▼aoctahedron distortion▼apseudo-capacitors▼asolid-solutions; 밀도 함수 이론▼a얀-텔러 효과▼a팔면체 뒤틀림▼a슈도커패시터▼a고용체

URI
http://hdl.handle.net/10203/265565
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=849856&flag=dissertation
Appears in Collection
EEW-Theses_Master(석사논문)
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