Ghodbane O.Ataherian F.Wu N.-L.Favier F.2019-05-172019-05-17201203787753https://scholars.lib.ntu.edu.tw/handle/123456789/408992Structural 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.Charge-discharge mechanismIn situ X-ray diffractionManganese dioxidesMicrostructural material changesSupercapacitorSynchrotronjournal article10.1016/j.jpowsour.2012.01.1032-s2.0-84857912679https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857912679&doi=10.1016%2fj.jpowsour.2012.01.103&partnerID=40&md5=cbe54bf391efbb99c8ab80c980ce715a