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Author: Presser, Volker × End date: 2019 × Start date: 2016 × Type: article × Version: publishedVersion × Subject: carbon onions ×

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    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.
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    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.