title: Dry-Processed, Binder-Free Holey Graphene Electrodes for Supercapacitors with Ultrahigh Areal Loadings.
abstract: For commercial applications, the need for smaller footprint energy storage devices requires more energy to be stored per unit area. Carbon nanomaterials, especially graphene, have been studied as supercapacitor electrodes and can achieve high gravimetric capacities affording high gravimetric energy densities. However, most nanocarbon-based electrodes exhibit a significant decrease in their areal capacitances when scaled to the high mass loadings typically used in commercially available cells (∼10 mg/cm2). One of the reasons for this behavior is that the additional surface area in thick electrodes is not readily accessible by electrolyte ions due to the large tortuosity. Furthermore, the fabrication of such electrodes often involves complicated processes that limit the potential for mass production. Here, holey graphene electrodes for supercapacitors that are scalable in both production and areal capacitance are presented. The lateral surface porosity on the graphene sheets was created using a facile single-step air oxidation method, and the resultant holey graphene was compacted under ambient conditions into mechanically robust monolithic shapes that can be directly used as binder-free electrodes. In comparison, pristine graphene discs under similar binder-free compression molding conditions were extremely brittle and thus not deemed useful for electrode applications. The coin cell supercapacitors, based on these holey graphene electrodes exhibited small variations in gravimetric capacitance over a wide range of areal mass loadings (∼1-30 mg/cm2) at current densities as high as 30 mA/cm2, resulting in the near-linear increase of the areal capacitance (F/cm2) with the mass loading. The prospects of the presented method for facile binder-free ultrathick graphene electrode fabrication are discussed.
authors.affiliation: NASA Interns, Fellows, and Scholars (NIFS) Program, NASA Langley Research Center , Hampton, Virginia 23681, United States.
authors.forename: Evan D
authors.initials: ED
authors.lastname: Walsh
authors.affiliation: Department of Materials Science and Engineering, University of Maryland , College Park, Maryland 20742, United States.
authors.forename: Xiaogang
authors.initials: X
authors.lastname: Han
authors.affiliation: NASA Interns, Fellows, and Scholars (NIFS) Program, NASA Langley Research Center , Hampton, Virginia 23681, United States.|Department of Materials Science and Engineering, University of Maryland , College Park, Maryland 20742, United States.
authors.forename: Steven D
authors.initials: SD
authors.lastname: Lacey
authors.affiliation: National Institute of Aerospace , 100 Exploration Way, Hampton, Virginia 23666-6147, United States.
authors.forename: Jae-Woo
authors.initials: JW
authors.lastname: Kim
authors.affiliation: Advanced Materials and Processing Branch, NASA Langley Research Center , Mail Stop 226, Hampton, Virginia 23681-2199, United States.
authors.forename: John W
authors.initials: JW
authors.lastname: Connell
authors.affiliation: Department of Materials Science and Engineering, University of Maryland , College Park, Maryland 20742, United States.
authors.forename: Liangbing
authors.initials: L
authors.lastname: Hu
authors.affiliation: National Institute of Aerospace , 100 Exploration Way, Hampton, Virginia 23666-6147, United States.|Department of Applied Science, The College of William and Mary , Williamsburg, Virginia 23185, United States.
authors.forename: Yi
authors.initials: Y
authors.lastname: Lin
keywords: areal capacitance; dry processing; graphene; holey graphene; supercapacitors