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Na0.97KFe(SO4)2: Iron-based sulfate cathode material with outstanding cyclability and power capability for Na-ion batteries

Abstract

In this work, a novel cathode material for Na-ion batteries, KFe(SO4)2, was successfully prepared via slow evaporation and a low-temperature process, and its outstanding electrochemical performance was demonstrated. Based on the structural information of KFe(SO4)2 obtained from Rietveld refinement of X-ray diffraction data, the possible atomic sites for Na ions entering the structure were verified using bond-valence sum energy maps. Electrochemical measurements and X-ray absorption near-edge structure analyses revealed that ~0.97 mol Na ions can be reversibly (de)intercalated into the structure via the Fe3+/Fe2+ redox reaction. The average redox potential of KFe(SO4)2 was shown to be ~3.27 V (vs. Na+/Na), which is higher than that of other Fe-based phosphates owing to the inductive effect by (SO4)2−. It was verified that the specific capacity of KFe(SO4)2 at C/10 was ~85mAh g-1. At 10C (full charge/discharge in 12 min), ~53% of its capacity measured at C/10 was retained. In addition, up to ~99% of its initial capacity was retained over 200 cycles at 1C with a high coulombic efficiency of 99.3097%, which was attributed to the negligible volume change (~1.8%) during charge/discharge.

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Publication details

The article was received on 19 Jun 2018, accepted on 08 Aug 2018 and first published on 09 Aug 2018


Article type: Paper
DOI: 10.1039/C8TA05854G
Citation: J. Mater. Chem. A, 2018, Accepted Manuscript
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    Na0.97KFe(SO4)2: Iron-based sulfate cathode material with outstanding cyclability and power capability for Na-ion batteries

    W. Ko, T. Park, H. Park, Y. Lee, K. E. Kee and J. Kim, J. Mater. Chem. A, 2018, Accepted Manuscript , DOI: 10.1039/C8TA05854G

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