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Issue 44, 2015
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From kröhnkite- to alluaudite-type of structure: novel method of synthesis of sodium manganese sulfates with electrochemical properties in alkali-metal ion batteries

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Abstract

The alluaudite-type of structure is of huge research interest as an open matrix ensuring fast alkali-metal ion mobility, a property that could contribute to the development of novel electrode materials for rechargeable alkali-metal ion batteries. In this contribution, we provide new data on the formation of well-crystallized sodium manganese sulfates Na2+δMn2−δ/2(SO4)3 with an alluaudite-type of structure by simple dehydratation of the corresponding dihydrate Na2Mn(SO4)3·2H2O with a kröhnkite-type of structure. The structure of Na2+δMn2−δ/2(SO4)3 is determined on the basis of Rietveld refinement of powder XRD patterns, infrared (IR) and Raman spectroscopy and electron paramagnetic resonance at X- and Q-band frequencies (EPR). From a structural point of view, the release of two H2O molecule from the kröhnkite phase takes place by a transformation of the infinite [Mn(SO4)2(H2O)2] chains into Mn2O10 dimers bounded by distorted Na(1)O-polyhedra. The anhydrous sulfates are able to participate in the electrochemical reaction delivering a reversible capacity of 135 mA h g−1, when they are used as cathode materials in lithium ion cells. The stability of the alluaudite phase Na2+δMn2−δ/2(SO4)3 in the lithium electrolyte solution and the mechanism of the electrochemical reaction are discussed on the basis of ex situ EPR, IR and Raman spectroscopy. This is a first report on electrochemical activity of manganese-based sulfate with an alluaudite-type of structure.

Graphical abstract: From kröhnkite- to alluaudite-type of structure: novel method of synthesis of sodium manganese sulfates with electrochemical properties in alkali-metal ion batteries

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Publication details

The article was received on 09 Sep 2015, accepted on 25 Sep 2015 and first published on 25 Sep 2015


Article type: Paper
DOI: 10.1039/C5TA07204B
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Citation: J. Mater. Chem. A, 2015,3, 22287-22299
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    From kröhnkite- to alluaudite-type of structure: novel method of synthesis of sodium manganese sulfates with electrochemical properties in alkali-metal ion batteries

    D. Marinova, V. Kostov, R. Nikolova, R. Kukeva, E. Zhecheva, M. Sendova-Vasileva and R. Stoyanova, J. Mater. Chem. A, 2015, 3, 22287
    DOI: 10.1039/C5TA07204B

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