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.
Angew Chem Int Ed Engl. 2016 Mar 14;55(12):3958-62. doi: 10.1002/anie.201511452. Epub 2016 Feb 17.
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.
当镍、钴和锰混合形成固溶体时，观察到金属氧化物的异常高赝电容。通过 X 射线吸收近边光谱（XANES）分析，确定 Ni 的更大氧化还原摆动是赝电容增大的原因。从头算 DFT 计算表明，由于多种过渡金属共存而产生的变价物种可以导致[NiO6]八面体的永久局部变形。由于这种变形打破了 Ni(2+)的简并 eg 能级，因此在充放电过程中，Ni(2+/3+)氧化还原翻转所需的 Jahn-Teller 晶格不稳定性可以有效降低，从而导致电容显著增加。我们的发现强调了理解与局部结构变形相关的结构-性能相关性对于改善赝电容器性能的重要性。
