Filters

2016 - 20174

More filters

20194
Reset filters

Settings

Author: Presser, Volker × End date: 2019 × Start date: 2019 × DDC: 620 × Type: Text × Publisher: Cambridge : Royal Society of Chemistry ×

Search Results

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Review: Carbon onions for electrochemical energy storage
    (Cambridge : Royal Society of Chemistry, 2016) Zeiger, Marco; Jäckel, Nicolas; Mochalin, Vadym N.; Presser, Volker
    Carbon onions are a relatively new member of the carbon nanomaterials family. They consist of multiple concentric fullerene-like carbon shells which are highly defective and disordered. Due to their small size of typically below 10 nm, the large external surface area, and high conductivity they are used for supercapacitor applications. As electrode materials, carbon onions provide fast charge/discharge rates resulting in high specific power but present comparatively low specific energy. They improve the performance of activated carbon electrodes as conductive additives and show suitable properties as substrates for redox-active materials. This review provides a critical discussion of the electrochemical properties of different types of carbon onions as electrode materials. It also compares the general advantages and disadvantages of different carbon onion synthesis methods. The physical and chemical properties of carbon onions, in particular nanodiamond-derived carbon onions, are described with emphasis on those parameters especially important for electrochemical energy storage systems, including the structure, conductivity, and porosity. Although the primary focus of current research is on electrode materials for supercapacitors, the use of carbon onions as conductive additives and for redox-active species is also discussed.
  • Thumbnail Image
    Item
    Influence of carbon substrate on the electrochemical performance of carbon/manganese oxide hybrids in aqueous and organic electrolytes
    (Cambridge : Royal Society of Chemistry, 2016) Zeiger, Marco; Fleischmann, Simon; Krüner, Benjamin; Tolosa, Aura; Bechtel, Stephan; Baltes, Mathias; Schreiber, Anna; Moroni, Riko; Vierrath, Severin; Thiele, Simon; Presser, Volker
    Manganese oxide presents very promising electrochemical properties as an electrode material in supercapacitors, but there remain important open questions to guide further development of the complex manganese oxide/carbon/electrolyte system. Our work addresses specifically the influence of carbon ordering and the difference between outer and inner porosity of carbon particles for the application in aqueous 1 M Na2SO4 and 1 M LiClO4 in acetonitrile. Birnessite-type manganese oxide was hydrothermally hybridized on two kinds of carbon onions with only outer surface area and different electrical conductivity, and conventional activated carbon with a high inner porosity. Carbon onions with a high degree of carbon ordering, high conductivity, and high outer surface area were identified as the most promising material, yielding 179 F g−1. Pore blocking in activated carbon yields unfavorable electrochemical performances. The highest specific energy of 16.4 W h kg−1 was measured for a symmetric full-cell arrangement of manganese oxide coated high temperature carbon onions in the organic electrolyte. High stability during 10 000 cycles was achieved for asymmetric full-cells, which proved as a facile way to enhance the electrochemical performance stability.
  • Thumbnail Image
    Item
    Carbon onion–sulfur hybrid cathodes for lithium–sulfur batteries
    (Cambridge : Royal Society of Chemistry, 2017) Choudhury, Soumyadip; Zeiger, Marco; Massuti-Ballester, Pau; Fleischmann, Simon; Formanek, Petr; Borchardt, Lars; Presser, Volker
    In this study, we explore carbon onions (diameter below 10 nm), for the first time, as a substrate material for lithium sulfur cathodes. We introduce several scalable synthesis routes to fabricate carbon onion–sulfur hybrids by adopting in situ and melt diffusion strategies with sulfur fractions up to 68 mass%. The conducting skeleton of agglomerated carbon onions proved to be responsible for keeping active sulfur always in close vicinity to the conducting matrix. Therefore, the hybrids are found to be efficient cathodes for Li–S batteries, yielding 97–98% Coulombic efficiency over 150 cycles with a slow fading of the specific capacity (ca. 660 mA h g−1 after 150 cycles) in long term cycle test and rate capability experiments.
  • Thumbnail Image
    Item
    Carbon onion / sulfur hybrid cathodes via inverse vulcanization for lithium sulfur batteries
    (Cambridge : Royal Society of Chemistry, 2017) Choudhury, Soumyadip; Srimuk, Pattarachai; Raju, Kumar; Tolosa, Aura; Fleischmann, Simon; Zeiger, Marco; Ozoemena, Kenneth I.; Borchardt, Lars; Presser, Volker
    A sulfur–1,3-diisopropenylbenzene copolymer was synthesized by ring-opening radical polymerization and hybridized with carbon onions at different loading levels. The carbon onion mixing was assisted by shear in a two-roll mill to capitalize on the softened state of the copolymer. The sulfur copolymer and the hybrids were thoroughly characterized in structure and chemical composition, and finally tested by electrochemical benchmarking. An enhancement of specific capacity was observed over 140 cycles at higher content of carbon onions in the hybrid electrodes. The copolymer hybrids demonstrate a maximum initial specific capacity of 1150 mA h gsulfur−1 (850 mA h gelectrode−1) and a low decay of capacity to reach 790 mA h gsulfur−1 (585 mA h gelectrode−1) after 140 charge/discharge cycles. All carbon onion/sulfur copolymer hybrid electrodes yielded high chemical stability, stable electrochemical performance superior to conventional melt-infiltrated reference samples having similar sulfur and carbon onion content. The amount of carbon onions embedded in the sulfur copolymer has a strong influence on the specific capacity, as they effectively stabilize the sulfur copolymer and sterically hinder the recombination of sulfur species to the S8 configuration.