Interrelation between inhomogeneity and cyclability in O3‐NaFe1/2Co1/2O2 |
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| Authors: | Kaoru Amaha Wataru Kobayashi Shota Akama Kazutaka Mitsuishi Yutaka Moritomo |
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| Institution: | 1. Graduate School of Pure and Applied Science, University of Tsukuba, Tsukuba, Japan;2. Center for Integrated Research in Fundamental Science and Engineering (CiRfSE), University of Tsukuba, Tsukuba, Japan;3. Tsukuba Research Center for Interdisciplinary Materials Science (TIMS), University of Tsukuba, Tsukuba, Japan;4. Research Center for Advanced Measurement and Characterization, National Institute for Materials Science, Tsukuba, Japan |
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| Abstract: | O3‐NaFe1/2Co1/2O2 shows initial capacity of 160 mAh/g and an average operating voltage of 3.1 V (vs. Na) with good cyclability, and is a promising candidate of the cathode materials for sodium‐ion secondary batteries (SIBs). Here, we found that the cyclability of the slowly‐cooled sample is much worse than that of quenched one, even though the former sample keeps the O3‐type structure. The energy dispersive X‐ray spectroscopy (EDX) images suggest that the slow‐cooled sample (Nax Fe1–yCoy O2) is inhomogeneous in the Fe concentration (1 – y), perhaps triggered by the Na deficiency (1 – x). We ascribed the poor cyclability in the slowly‐cooled sample to the concentration inhomogeneity (Δy). The Δy is further responsible for the fluctuation of the lattice constants (a and c), as revealed by the Williamson–Hall plot. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) |
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| Keywords: | sodium‐ion secondary batteries layered oxides inhomogeneity concentration cyclability O3‐NaFe1/2Co1/2O2 |
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