title: Redox Active Cation Intercalation/Deintercalation in Two-Dimensional Layered MnO2Nanostructures for High-Rate Electrochemical Energy Storage.
abstract: Two-dimensional (2D) layered materials with a high intercalation pseudocapacitance have long been investigated for Li+-ion-based electrochemical energy storage. By contrast, the exploration of guest ions other than Li+has been limited, although promising. The present study investigates intercalation/deintercalation behaviors of various metal ions in 2D layered MnO2with various interlayer distances, K-birnessite nanobelt (K-MnO2), its protonated form (H-MnO2), and a freeze-dried sample of exfoliated nanosheets. Series of metal ions, such as monovalent Li+, Na+, and K+and divalent Mg2+, exhibit reversible intercalation during charge/discharge cycling, delivering high-rate pseudocapacitances. In particular, the freeze-dried MnO2of exfoliated nanosheets restacked with the largest interlayer spacing and a less compact 3D network exhibits the best rate capability and a stable cyclability over 5000 cycles. Both theoretical calculation and kinetic analysis reveal that the increased interlayer distance facilitates the fast diffusion of cations in layered MnO2hosts. The results presented herein provide a basis for the controllable synthesis of layered nanostructures for high-rate electrochemical energy storage using various single- and multivalent ions.
authors.affiliation: International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS) , Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan.
authors.forename: Pan
authors.identifier: http://orcid.org/0000-0001-9483-6535
authors.initials: P
authors.lastname: Xiong
authors.affiliation: International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS) , Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan.
authors.forename: Renzhi
authors.initials: R
authors.lastname: Ma
authors.affiliation: International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS) , Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan.
authors.forename: Nobuyuki
authors.identifier: http://orcid.org/0000-0002-9395-6751
authors.initials: N
authors.lastname: Sakai
authors.affiliation: International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS) , Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan.
authors.forename: Xueyin
authors.initials: X
authors.lastname: Bai
authors.affiliation: Department of Materials Science & Engineering, Royal Institute of Technology , SE-100 44 Stockholm, Sweden.
authors.forename: Shen
authors.initials: S
authors.lastname: Li
authors.affiliation: International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS) , Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan.
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Sasaki
keywords: cation intercalation/deintercalation; interlayer spacing; metal ion-based energy storage; rate capability; two-dimensional layered nanostructures