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Highlighting the Reversible Manganese Electroactivity in Na‐Rich Manganese Hexacyanoferrate Material for Li‐ and Na‐Ion Storage
Author(s) -
Mullaliu Angelo,
Asenbauer Jakob,
Aquilanti Giuliana,
Passerini Stefano,
Giorgetti Marco
Publication year - 2020
Publication title -
small methods
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.66
H-Index - 46
ISSN - 2366-9608
DOI - 10.1002/smtd.201900529
Subject(s) - manganese , x ray absorption spectroscopy , prussian blue , ion , absorption spectroscopy , electrochemistry , chemistry , absorption (acoustics) , inorganic chemistry , redox , metal , spectroscopy , sodium , materials science , electrode , physics , organic chemistry , quantum mechanics , composite material
Abstract The electroactivity of sodium‐rich manganese hexacyanoferrate (MnHCF) material constituted of only abundant elements, as insertion host for Li‐ and Na‐ions is herein comprehensively discussed. This material features high specific capacities (>130 mAh g −1 ) at high potentials when compared to other materials of the same class, i.e., Prussian blue analogs. The reversible electronic and structural modifications occurring during ion release/uptake, which are responsible for such high specific capacity, are revealed herein. The in‐depth electronic and structural analysis carried out combining X‐ray diffraction and X‐ray absorption spectroscopy (XAS), demonstrates that both Fe and Mn sites are involved in the electrochemical process, being the high delivered capacity the result of a reversible evolution in oxidation states of the metallic centers (Fe 3+ /Fe 2+ and Mn 2+ /Mn 3+ ). Along with the Mn 2+ /Mn 3+ oxidation, the Mn local environment experiences a substantial yet reversible Jahn–Teller effect, being the equatorial Mn‐N distances shrunk by 10% (2.18 Å → 1.96 Å). Na‐rich MnHCF material offers slightly higher performance upon uptake and release of Na‐ions (469 Wh kg −1 ) than Li‐ions (457 Wh kg −1 ), being, however, the electronic and structural transformation independent of the adopted medium, as observed by XAS spectroscopy.