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Ruoff, Rodney S.
Center for Multidimensional Carbon Materials (CMCM)
Research Interests
  • Next generation carbons, ultrathin sp3-bonded carbon sheets, negative curvature (‘Schwartzites’) carbons, sp3/sp2 hybrid carbon materials, model compounds for novel carbon materials, reaction mechanisms

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Structural Directed Growth of Ultrathin Parallel Birnessite on β-MnO2 for High-Performance Asymmetric Supercapacitors

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Title
Structural Directed Growth of Ultrathin Parallel Birnessite on β-MnO2 for High-Performance Asymmetric Supercapacitors
Author
Zhu, ShijinLi, LiLiu, JiabinWang, HongtaoWang, TianZhang, YuxinZhang, LiliRuoff, Rodney S.Dong, Fan
Keywords
core− shell structure;  birnessite;  asymmetric supercapacitor;  nanocomposite;  energy storage mechanism
Issue Date
201802
Publisher
AMER CHEMICAL SOC
Citation
ACS NANO, v.12, no.2, pp.1033 - 1042
Abstract
Two-dimensional birnessite has attracted attention for electrochemical energy storage because of the presence of redox active Mn4+/Mn3+ ions and spacious interlayer channels available for ions diffusion. However, current strategies are largely limited to enhancing the electrical conductivity of birnessite. One key limitation affecting the electrochemical properties of birnessite is the poor utilization of the MnO6 unit. Here, we assemble β-MnO2/birnessite core-shell structure that exploits the exposed crystal face of β-MnO2 as the core and ultrathin birnessite sheets that have the structure advantage to enhance the utilization efficiency of the Mn from the bulk. Our birnessite that has sheets parallel to each other is found to have unusual crystal structure with interlayer spacing, Mn(III)/Mn(IV) ratio and the content of the balancing cations differing from that of the common birnessite. The substrate directed growth mechanism is carefully investigated. The as-prepared core-shell nanostructures enhance the exposed surface area of birnessite and achieve high electrochemical performances (for example, 657 F g-1 in 1 M Na2SO4 electrolyte based on the weight of parallel birnessite) and excellent rate capability over a potential window of up to 1.2 V. This strategy opens avenues for fundamental studies of birnessite and its properties and suggests the possibility of its use in energy storage and other applications. The potential window of an asymmetric supercapacitor that was assembled with this material can be enlarged to 2.2 V (in aqueous electrolyte) with a good cycling ability.
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DOI
http://dx.doi.org/10.1021/acsnano.7b03431
ISSN
1936-0851
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