title: Hydrothermally Oxidized Single-Walled Carbon Nanotube Networks for High Volumetric Electrochemical Energy Storage.
abstract: Improving volumetric energy density is one of the major challenges in nanostructured carbon electrodes for electrochemical energy storage device applications. Herein, a simple hydrothermal oxidation process of single-walled carbon nanotube (SWNT) networks in dilute nitric acid is reported, enabling simultaneous physical densification and chemical functionalization of the as-assembled randomly-packed SWNT films. After the hydrothermal oxidation process, the density of the SWNT films increases from 0.63 to 1.02 g cm(-3) and a considerable amount of redox-active oxygen functional groups are introduced on the surface of the SWNTs. The functionalized SWNT films are used as positive electrodes against Li metal negative electrodes for potential Li-ion capacitors or Li-ion battery applications. The functionalized SWNT electrodes deliver high volumetric as well as gravimetric capacities, 154 Ah L(-1) and 152 mAh g(-1) , respectively, owing to the surface redox reactions between the introduced oxygen functional groups and Li ions. In addition, these electrodes exhibit a remarkable rate-capability by retaining its high capacity of 94 Ah L(-1) (92 mAh g(-1) ) at a high discharge rate of 10 A g(-1) . These results demonstrate the simple hydrothermal oxidation process as an attractive strategy for improving the volumetric performance of nanostructured carbon electrodes.
authors.affiliation: George. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA.
authors.forename: Tianyuan
authors.initials: T
authors.lastname: Liu
authors.affiliation: School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA.
authors.forename: Amir A Bakhtiary
authors.initials: AA
authors.lastname: Davijani
authors.affiliation: Department of Physics and the Texas Center for Superconductivity, University of Houston, Houston, TX, 77004, USA.
authors.forename: Jingying
authors.initials: J
authors.lastname: Sun
authors.affiliation: Department of Physics and the Texas Center for Superconductivity, University of Houston, Houston, TX, 77004, USA.
authors.forename: Shuo
authors.initials: S
authors.lastname: Chen
authors.affiliation: School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA.
authors.forename: Satish
authors.initials: S
authors.lastname: Kumar
authors.affiliation: George. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA.
authors.forename: Seung Woo
authors.initials: SW
authors.lastname: Lee
keywords: carbon nanotubes; electrochemical energy storage; hydrothermal oxidation; positive electrodes; volumetric performance