title: Hierarchical Electrospun and Cooperatively Assembled Nanoporous Ni/NiO/MnOx/Carbon Nanofiber Composites for Lithium Ion Battery Anodes.
abstract: A facile method to fabricate hierarchically structured fiber composites is described based on the electrospinning of a dope containing nickel and manganese nitrate salts, citric acid, phenolic resin, and an amphiphilic block copolymer. Carbonization of these fiber mats at 800 °C generates metallic Ni-encapsulated NiO/MnOx/carbon composite fibers with average BET surface area (150 m(2)/g) almost 3 times higher than those reported for nonporous metal oxide nanofibers. The average diameter (∼900 nm) of these fiber composites is nearly invariant of chemical composition and can be easily tuned by the dope concentration and electrospinning conditions. The metallic Ni nanoparticle encapsulation of NiO/MnOx/C fibers leads to enhanced electrical conductivity of the fibers, while the block copolymers template an internal nanoporous morphology and the carbon in these composite fibers helps to accommodate volumetric changes during charging. These attributes can lead to lithium ion battery anodes with decent rate performance and long-term cycle stability, but performance strongly depends on the composition of the composite fibers. The composite fibers produced from a dope where the metal nitrate is 66% Ni generates the anode that exhibits the highest reversible specific capacity at high rate for any composition, even when including the mass of the nonactive carbon and Ni(0) in the calculation of the capacity. On the basis of the active oxides alone, near-theoretical capacity and excellent cycling stability are achieved for this composition. These cooperatively assembled hierarchical composites provide a platform for fundamentally assessing compositional dependencies for electrochemical performance. Moreover, this electrospinning strategy is readily scalable for the fabrication of a wide variety of nanoporous transition metal oxide fibers.
authors.affiliation: Department of Polymer Engineering and ‡Department of Polymer Science, University of Akron , Akron, Ohio 44325, United States.
authors.forename: Sarang M
authors.initials: SM
authors.lastname: Bhaway
authors.affiliation: Department of Polymer Engineering and ‡Department of Polymer Science, University of Akron , Akron, Ohio 44325, United States.
authors.forename: Yu-Ming
authors.initials: YM
authors.lastname: Chen
authors.affiliation: Department of Polymer Engineering and ‡Department of Polymer Science, University of Akron , Akron, Ohio 44325, United States.
authors.forename: Yuanhao
authors.initials: Y
authors.lastname: Guo
authors.affiliation: Department of Polymer Engineering and ‡Department of Polymer Science, University of Akron , Akron, Ohio 44325, United States.
authors.forename: Pattarasai
authors.initials: P
authors.lastname: Tangvijitsakul
authors.affiliation: Department of Polymer Engineering and ‡Department of Polymer Science, University of Akron , Akron, Ohio 44325, United States.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Soucek
authors.affiliation: Department of Polymer Engineering and ‡Department of Polymer Science, University of Akron , Akron, Ohio 44325, United States.
authors.forename: Miko
authors.initials: M
authors.lastname: Cakmak
authors.affiliation: Department of Polymer Engineering and ‡Department of Polymer Science, University of Akron , Akron, Ohio 44325, United States.
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Department of Polymer Engineering and ‡Department of Polymer Science, University of Akron , Akron, Ohio 44325, United States.
authors.forename: Bryan D
authors.initials: BD
authors.lastname: Vogt
keywords: block copolymer; electrochemical energy storage; electrospinning; nanofibers; ordered mesopores; self-assembly