title: Enhanced Pseudocapacitance in Multicomponent Transition-Metal Oxides by Local Distortion of Oxygen Octahedra.
abstract: Anomalously high pseudocapacitance of a metal oxide was observed when Ni, Co, and Mn were mixed in a solid solution. Analysis by X-ray absorption near-edge spectroscopy (XANES) identified a wider redox swing of Ni as the origin of the enlarged pseudocapacitance. Ab initio DFT calculations revealed that aliovalent species resulting from the copresence of multiple transition metals can generate permanent local distortions of [NiO6] octahedra. As this type of distortion breaks the degenerate eg level of Ni(2+), the Jahn-Teller lattice instability necessary for the Ni(2+/3+) redox flip can be effectively diminished during charge-discharge, thus resulting in the significantly increased capacitance. Our findings highlight the importance of understanding structure-property correlation related to local structural distortions in improving the performance of pseudocapacitors.
authors.affiliation: Graduate School of EEWS, KAIST Institute NanoCentury, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea.
authors.forename: Hyeon Jeong
authors.initials: HJ
authors.lastname: Lee
authors.affiliation: Graduate School of EEWS, KAIST Institute NanoCentury, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea.
authors.forename: Ji Hoon
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Graduate School of EEWS, KAIST Institute NanoCentury, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea. sychung@kaist.ac.kr.
authors.forename: Sung-Yoon
authors.initials: SY
authors.lastname: Chung
authors.affiliation: Graduate School of EEWS, KAIST Institute NanoCentury, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea. jangwookchoi@kaist.ac.kr.
authors.forename: Jang Wook
authors.initials: JW
authors.lastname: Choi
keywords: Jahn-Teller distortion; electrochemistry; octahedron distortion; pseudocapacitors; solid solutions