Interrelation between inhomogeneity and cyclability in O3‐NaFe1/2Co1/2O2. Issue 1 (4th November 2016)

• Record Type: Journal Article
• Authors: Amaha, Kaoru; Kobayashi, Wataru; Akama, Shota; Mitsuishi, Kazutaka; Moritomo, Yutaka
• Is Part Of: Physica status solidi. Volume 11:Issue 1(2017)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2016-11-04
• Subjects: sodium‐ion secondary batteries -- layered oxides -- inhomogeneity -- concentration -- cyclability -- O3‐NaFe1/2Co1/2O2; Solid state physics -- Periodicals; 530.4105
• DOI: 10.1002/pssr.201600284
• Languages: English
• ISSNs: 1862-6254

Abstract

Abstract : O3‐NaFe1/2 Co1/2 O2 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 (Na x Fe1– y Co y 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 (Δ y ). The Δ y 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) Abstract : O3‐NaFe1/2 Co1/2 O2 is a promising candidate of cathode materials for sodium‐ion secondary batteries (SIBs). Its battery property, however, strongly depends on the thermal process of the material. The authors found that the slowly‐cooled sample shows inhomogeneity of the Fe concentration and lattice constants, even though it keeps the O3‐type structure. The inhomogeneity is responsible for the poor cyclability of the slowly‐cooled sample.