Journal of Power Sources, Feb 1, 2014, Vol.247, p.391(5)
To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jpowsour.2013.08.123 Byline: Ayuko Kitajou, Junpei Yamaguchi, Satoshi Hara, Shigeto Okada Abstract: The structure changes of iron disulfide (FeS.sub.2) during discharge/charge process were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and synchrotron-based X-ray adsorption near the edge structure (XANES). Although the cyclability of the FeS.sub.2/Na battery is poor, FeS.sub.2/Na battery has a large first discharge capacity of 758 mA h g.sup.-1. It corresponds to 85% of the theoretical capacity based on the 4.0 Na reaction per FeS.sub.2 (893 mA h g.sup.-1). According to the Fe K-edge XANES spectra of discharged FeS.sub.2 pellets, there were no clear traces of iron valence change. However, the clear S K-edge jump shifted to lower energy with increasing Na content in FeS.sub.2. This is because the binding energy of S 1s electrons decrease as the oxidation number of S decreases, suggesting that the charge neutrality of the cathode after 2.0 Na discharge is kept by an S valence change from (S-S).sup.2- to S.sup.2-. Moreover, Na.sub.2S diffraction peaks were detected at the 3.0 Na discharged state as a trace of Na conversion reaction in the FeS.sub.2 cathode. Author Affiliation: (a) Research and Education Center of Carbon Resources, Kyushu University, 6-1 Kasuga-koen, Kasuga 816-8580, Japan (b) Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasuga-koen, Kasuga 816-8580, Japan (c) Institute for Materials Chemistry and Engineering, Kyushu University, 6-1 Kasuga-koen, Kasuga 816-8580, Japan Article History: Received 24 June 2013; Revised 21 August 2013; Accepted 26 August 2013
Sulfur Compounds ; X-ray Spectroscopy ; Batteries ; Adsorption
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