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Abstract: Electrochemical behavior of carbon black (CB) additives in 1 M LiPF6 EC/DEC (3:7 vol.) electrolyte in the operation potential range of positive electrodes in Li-ion cells was investigated. Various carbon blacks display noticeable electrochemical activity towards intercalation and electrolyte oxidation at potentials >4.0 V vs. Li/Li+. In situ X-ray diffraction, Raman spectroscopy, and ex situ scanning electron microscopy and Fourier Transform Infrared (FTIR) spectroscopy showed that repetitive intercalation/deintercalation of anions leads to structural alteration and degradation of carbon black nanoparticles. The mechanism of these interfacial processes on CB electrodes and their implications for electrochemical performance of high-voltage Li-ion electrodes during long-term cycling is evaluated. [Copyright &y& Elsevier]

Abstract: Graphene single nanosheet (GNS) is synthesized from graphite by chemical oxidation and thermal exfoliation at 1000 °C and confirmed by X-ray diffraction analysis. Scanning electron and transmission electron microscope images clearly show the lateral expansion of graphite sheet and uniform dispersion of Pt nanoparticles on GNS. Fourier transform infrared and X-ray photoelectron spectroscopy analyses are conducted for surface properties of GNS such as oxygenated functional groups. Cyclic voltammetric analysis shows that electrochemical active surface areas (ECSAs) for Pt/GNS, commercial Pt/Vulcan XC-72 carbon black and Pt-incorporated onto commercial carbon black (Pt/CB) prepared in the laboratory are 33.1 m2 g−1, 23.5 m2 g−1 and 22.5 m2 g−1, respectively. Because of significant restacking of Pt/GNS sheets, carbon black (CB) with different content is intercalated between Pt/GNS as a spacer. The ECSAs of Pt/GNS, Pt/GNS/CB20, Pt/GNS/CB30 and Pt/GNS/CB40 are evaluated to be 31.5 m2 g−1, 28.6 m2 g−1, 38.8 m2 g−1 and 30.4 m2 g−1, respectively. The cell performance highly depends on CB content and Pt/GNS/CB with 30 wt.% of CB content shows the best cell performance of 400 mA cm−2. [Copyright &y& Elsevier]