Solid electrolyte based on silicate matrix solvated by tetraalkylammonium salt solution in organic polar solvent
By Poling, Steven A.; Nelson, Carly R. & Martin, Steve W.
Published in Electrochimica Acta
2003
Abstract
Solid electrolyte composed of silicate matrix solvated by tetraalkylammonium salt solution in viscous organic polar solvent (propylene carbonate or sulpholane) was prepared by sol–gel method under controlled drying conditions. The organic solution was added directly to the tetramethoxysilane (TMOS) based sol. For comparison analogous material modified with pure solvent was prepared. Gel forms within 2–4 days depending on the solvent additive. The gelation time is longer than in the presence of lithium salt or pure solvent modified material. The obtained electrolyte is transparent and it loses about 12% its mass during first 30 days of aging. It was characterised by TGA, DSC, FTIR spectroscopy and impedance spectroscopy. The shape of TGA and DSC curve is similar to that of pure solvent. The IR spectra indicates silicate network formation with some silanol groups left. No indication of specific interactions between solute, solvent and silicate matrix has been found. The magnitude of electrical conductivity is close to 10-3 S cm-1 being one order of magnitude smaller than that of analogous liquid electrolyte. The electrical conductivity of silicate matrix modified with pure solvent is by two orders of magnitude smaller. The value of this parameter depends on time elapsed after gelation. Most substantial decrease is observed during first 10 days after gelation and it correlates with mass loss. The conductivity of TMOS based matrix solvated with pure solvent is another two orders of magnitude smaller. The obtained results indicate that silicate matrix is neutral reservoir for organic solvent. The porosity of the dried samples is to some extent affected by the presence of salt.