title: Ultrahigh-Capacity Lithium-Oxygen Batteries Enabled by Dry-Pressed Holey Graphene Air Cathodes.
abstract: Lithium-oxygen (Li-O2) batteries have the highest theoretical energy density of all the Li-based energy storage systems, but many challenges prevent them from practical use. A major obstacle is the sluggish performance of the air cathode, where both oxygen reduction (discharge) and oxygen evolution (charge) reactions occur. Recently, there have been significant advances in the development of graphene-based air cathode materials with a large surface area and catalytically active for both oxygen reduction and evolution reactions, especially with additional catalysts or dopants. However, most studies reported so far have examined air cathodes with a limited areal mass loading rarely exceeding 1 mg/cm2. Despite the high gravimetric capacity values achieved, the actual (areal) capacities of those batteries were far from sufficient for practical applications. Here, we present the fabrication, performance, and mechanistic investigations of high-mass-loading (up to 10 mg/cm2) graphene-based air electrodes for high-performance Li-O2batteries. Such air electrodes could be easily prepared within minutes under solvent-free and binder-free conditions by compression-molding holey graphene materials because of their unique dry compressibility associated with in-plane holes on the graphene sheet. Li-O2batteries with high air cathode mass loadings thus prepared exhibited excellent gravimetric capacity as well as ultrahigh areal capacity (as high as ∼40 mAh/cm2). The batteries were also cycled at a high curtailing areal capacity (2 mAh/cm2) and showed a better cycling stability for ultrathick cathodes than their thinner counterparts. Detailed post-mortem analyses of the electrodes clearly revealed the battery failure mechanisms under both primary and secondary modes, arising from the oxygen diffusion blockage and the catalytic site deactivation, respectively. These results strongly suggest that the dry-pressed holey graphene electrodes are a highly viable architectural platform for high-capacity, high-performance air cathodes in Li-O2batteries of practical significance.
authors.affiliation: National Institute of Aerospace , 100 Exploration Way, Hampton, Virginia 23666, United States.
authors.forename: Yi
authors.identifier: 0000-0002-1828-3518
authors.initials: Y
authors.lastname: Lin
authors.forename: Brandon
authors.initials: B
authors.lastname: Moitoso
authors.forename: Chalynette
authors.initials: C
authors.lastname: Martinez-Martinez
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: Steven D
authors.initials: SD
authors.lastname: Lacey
authors.affiliation: National Institute of Aerospace , 100 Exploration Way, Hampton, Virginia 23666, United States.
authors.forename: Jae-Woo
authors.initials: JW
authors.lastname: Kim
authors.affiliation: Department of Macromolecular Science and Engineering, Case School of Engineering, Case Western Reserve University , 10900 Euclid Avenue, Cleveland, Ohio 44106, United States.
authors.forename: Liming
authors.initials: L
authors.lastname: Dai
authors.affiliation: Department of Materials Science and Engineering, University of Maryland , College Park, Maryland 20742, United States.
authors.forename: Liangbing
authors.identifier: 0000-0002-9456-9315
authors.initials: L
authors.lastname: Hu
authors.forename: John W
authors.initials: JW
authors.lastname: Connell
keywords: Holey graphene; areal performance; binder-free; dry processing; lithium−oxygen batteries