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Carbon coatings can help to stabilize the electrochemical performance of high-energy anodes using silicon nanoparticles as the active material. In this work, the comparison of the behavior and chemical composition of the Solid Electrolyte Interphase (SEI) was carried out between Si nanoparticles and carbon-coated Si nanoparticles (Si@C). A combination of two complementary analytical techniques, Electrochemical Impedance Spectroscopy and X-ray Photoelectron Spectroscopy (XPS), was used to determine the intrinsic characteristics of the SEI. It was demonstrated that the SEI on Si particles is more resistive than the SEI on the Si@C particles. XPS demonstrated that the interface on the Si particles contains more oxygen when not covered with carbon, which shows that a protective layer of carbon helps to reduce the number of inorganic components, leading to more resistive SEI. The combination of those two analytical techniques is implemented to highlight the features and evolution of interfaces in different battery technologies. [ABSTRACT FROM AUTHOR]

We report a comparative study of two silica-based ionogel electrolytes for electrochemical cycling applications. The ionogels considered represent two classes of gel networks, a covalently formed network generated by the polymerization of tetramethoxysilane catalyzed by formic acid, and a network formed by weak intermolecular forces obtained by mixing fumed silica nanopowder with ionic liquid. In both cases, 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide is utilized as the ion conductor in the gel network. With increasing temperature it is shown that the electrochemical stability window is reduced, the conductivity of the electrolyte is increased, and the double layer capacitance is increased for both types of ionogels. Long-term stability of the two ionogels is excellent, with 90% capacitance retained after 10,000 repetitive CV cycles at 100 °C. Our results indicate that both of these ionogel electrolytes are promising for application in solid-state electrochemical systems at high temperature. [ABSTRACT FROM AUTHOR]