(LiCl)2-Al2O3-SiO2xerogels were prepared by a sol-gel process. The structure of the heat-treated xerogels was studied by powder X-ray diffraction, Fourier transform infrared spectroscopy, and 7Li, 89Si, and 27Al nuclear magnetic resonance techniques. 7Li NMR studies indicate two kinds of lithium ions in the xerogels: (a) polycrystalline LiCl dispersed in the pores of the xerogel and (b) lithium ions associated with nonbridging oxygens on the silica tetrahedra or associated with AlO4 −units. For the samples having the same lithium content (20 mol % (LiCl)2) the ionic conductivity increases with increasing Al2O3/SiO2ratio. This is attributed to the increasing concentration of lithium ions associated with tetrahedral A104 or nonbridging oxygens in the xerogel. A constant activation energy is observed when the (LiCl)2content increases from 10 to 20 mol % for samples having the sample Al2O3/SiO2ratio of 1/2. This constant activation energy is analyzed in terms of the competition between the decreasing jump distance tending to decrease activation energy and increasing Coulombic interaction tending to increase activation energy.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Materials Chemistry