Daniel Waszak

Physicochemical and morphological properties of hydrated silicas precipitated following alkoxysilane surface modification

Abstract Modified silicas were obtained by precipitation from aqueous solutions of sodium metasilicate and sulphuric acid. For the modification, silane coupling agents with various functional groups were applied, including aminosilane (AEAPTS), glycidoxysilane (GPTS), mercaptosilane (McPTS), and vinylsilane (VTMES). Extensive physicochemical evaluation of the obtained modified silicas was conducted, using FTIR, 29 Si CP MAS NMR and XPS techniques. The silica surface modification was proven to depend upon chemical reactions and to show intensity increasing with a rising concentration of a given modifier. A surface charge of the formed silica dispersions was also examined, by determining their zeta potential. Moreover, surface morphology, dispersion and particle size of the obtained silicas were evaluated, employing TEM electron microscopy and the technique of a dynamic light scattering (DLS). The studies demonstrated that application of hydrophobic type silanes for surface modification of the hydrated silicas restricted the intense tendency for agglomeration in the formed precipitated silicas.

Impact of selected supramolecular additives on the initial electrochemical lithium intercalation into graphite in propylene carbonate

Impact of silicon tripodand-type electrolyte additives and graphite pre-treatment agents on the electrochemical intercalation of lithium cations into graphite was investigated. Addition of Si-tripodand-type silanes to propylene carbonate-based electrolytes was found to suppress detrimental solvent co-intercalation and graphite exfoliation. Similar effects were observed for graphite pre-treated with the reported silane agents. It was observed that the presented supramolecular additives allow for the formation of effective passive layers on graphite during first charging, and thus can be considered as novel low-cost film-forming components for rechargeable lithium batteries.