|Title:||In situ crystallographic investigations of charge storage mechanisms in MnO 2-based electrochemical capacitors||Authors:||Ghodbane O.
|Keywords:||Charge-discharge mechanism;In situ X-ray diffraction;Manganese dioxides;Microstructural material changes;Supercapacitor;Synchrotron||Issue Date:||2012||Journal Volume:||206||Start page/Pages:||454-462||Source:||Journal of Power Sources||Abstract:||
Structural behaviors of four MnO 2 allotropes are investigated by in situ synchrotron X-ray diffraction analyses upon charge/discharge cycling in LiCl and KCl aqueous media. During the anodic/cathodic scans of the 2D birnessite electrode, the interlayer spacing respectively extend/contract along the z direction by ?0.2 ?. This behavior is associated to electrostatic attractive forces between charged framework layers and hydrated electrolyte cations. In contrast, the oxidation/reduction of the 3D spinel electrode lead to the contraction/swelling of (1 1 1) crystalline planes by ?0.05 ?. Manganese-oxygen distance changes induced by Mn(III)/Mn(IV) redox reactions are assigned to such a mechanism. Structural characterizations are focused on the (0 0 2), (2 1 1), (1 1 0) and (2 0 0) planes for MnO 2 cryptomelane, while (0 0 2) and (2 0 0) planes for MnO 2 OMS-5. The 1D cryptomelane and OMS-5 electrodes also exhibit contraction/swelling processes of their structures upon discharge/charge cycling associated to deintercalation/intercalation of hydrated electrolyte cations in their channels, respectively, driven by size/steric constraints. ? 2012 Elsevier B.V. All rights reserved.
|Appears in Collections:||化學工程學系|
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