title: Bivalence Mn5O8with hydroxylated interphase for high-voltage aqueous sodium-ion storage.
abstract: Aqueous electrochemical energy storage devices have attracted significant attention owing to their high safety, low cost and environmental friendliness. However, their applications have been limited by a narrow potential window (∼1.23 V), beyond which the hydrogen and oxygen evolution reactions occur. Here we report the formation of layered Mn5O8pseudocapacitor electrode material with a well-ordered hydroxylated interphase. A symmetric full cell using such electrodes demonstrates a stable potential window of 3.0 V in an aqueous electrolyte, as well as high energy and power performance, nearly 100% coulombic efficiency and 85% energy efficiency after 25,000 charge-discharge cycles. The interplay between hydroxylated interphase on the surface and the unique bivalence structure of Mn5O8suppresses the gas evolution reactions, offers a two-electron charge transfer via Mn2+/Mn4+redox couple, and provides facile pathway for Na-ion transport via intra-/inter-layer defects of Mn5O8.
authors.affiliation: Department of Chemical Engineering, University of New Hampshire, Durham, New Hampshire 03824, USA.
authors.forename: Xiaoqiang
authors.initials: X
authors.lastname: Shan
authors.affiliation: Department of Chemical Engineering, University of New Hampshire, Durham, New Hampshire 03824, USA.
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Charles
authors.affiliation: Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
authors.forename: Yinkai
authors.initials: Y
authors.lastname: Lei
authors.affiliation: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Ruimin
authors.initials: R
authors.lastname: Qiao
authors.affiliation: Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
authors.forename: Guofeng
authors.initials: G
authors.lastname: Wang
authors.affiliation: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Wanli
authors.identifier: 0000-0003-0666-8063
authors.initials: W
authors.lastname: Yang
authors.affiliation: Chemical and Engineering Materials Division, Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Mikhail
authors.initials: M
authors.lastname: Feygenson
authors.affiliation: Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: Dong
authors.identifier: 0000-0002-1921-6683
authors.initials: D
authors.lastname: Su
authors.affiliation: Department of Chemical Engineering, University of New Hampshire, Durham, New Hampshire 03824, USA.
authors.forename: Xiaowei
authors.identifier: 0000-0001-9547-7175
authors.initials: X
authors.lastname: Teng