Structural and electrochemical properties of iron- and nickel-substituted Li 2 MnO 3 cathodes in charged and discharged states
| Autor: | Hideka Shibuya, Kyosuke Doumae, Takashi Miyazaki, Sadanori Kuroshima, Ryota Yuge, Mitsuharu Tabuchi, Akio Toda, Noriyuki Tamura |
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| Rok vydání: | 2017 |
| Předmět: |
X-ray absorption spectroscopy
Valence (chemistry) Absorption spectroscopy Renewable Energy Sustainability and the Environment 020209 energy Inorganic chemistry Analytical chemistry Oxide Energy Engineering and Power Technology chemistry.chemical_element 02 engineering and technology 021001 nanoscience & nanotechnology Electrochemistry Redox Ion Nickel chemistry.chemical_compound chemistry 0202 electrical engineering electronic engineering information engineering Electrical and Electronic Engineering Physical and Theoretical Chemistry 0210 nano-technology |
| Zdroj: | Journal of Power Sources. 365:117-125 |
| ISSN: | 0378-7753 |
| Popis: | Structural change and the charge compensation mechanism of lithium-rich layered cathode (Li1.23Fe0.15Ni0.15Mn0.46O2) in charged and discharged states were investigated. Selected area electron diffraction analysis revealed that in discharged state, an initial structure composed of a single phase of monoclinic layered rock-salt changed to a mixture of hexagonal layered rock-salt and spinel-like structures. In charged state, the spinel-like phase became dominant as transition-metal ions migrate. 57Fe Mossbauer spectroscopy, X-ray absorption spectroscopy (XAS), and Soft-XAS showed that the valence of Fe and Ni ions approximately changed from Fe3+ to Fe3.2+ and Ni2+ to Ni3.5+ during charge-discharge, although Mn ions remained as Mn4+. Various oxidation states of oxide ions such as superoxide, peroxide, and hole states have also been detected in charged state. Considering that actual discharge capacity was 255 mAh/g, the contribution to charge compensation from the valence change of Fe and Ni ions was extremely small, and it only contributed to about one-third of total capacity. Therefore, the mechanism to yield high capacity of the Li1.23Fe0.15Ni0.15Mn0.46O2 cathode relates strongly to the redox reaction of oxide ions. Moreover, the decrease in capacity during charge-discharge cycling was mainly due to the irreversible redox reaction of Mn, Fe, and oxide ions. |
| Databáze: | OpenAIRE |
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