Lithium conduction in inorganic gel monoliths containing LiNO3 or LiBr at low temperatures

Abstract

Lithium conducting silica gels were prepared with LiNO3 and LiBr salts added at the beginning of the sol–gel process. The chemical compositions of the initial sols corresponded to the formula TMOS/H2O/HCl/LiX/MeOH=1:n:5×10−4:0.2:3 for n=4 and n=20, where LiX=LiNO3 or LiBr. The ionic conductivity of the gels and that of the relevant solutions was measured by impedance spectroscopy in the temperature range 170–300 K. The temperature dependence of the conductivity for gels with a large excess of water (n=20) followed the Arrhenius formula σT=σ0exp[−E/kT] at temperatures below ca. 210 K and above ca. 245 K with different values of σ0 and E in both ranges. The ionic conductivity of gels prepared from stoichiometric sols (n=4) varied with temperature according to the Vogel–Tammann–Fulcher (VTF) equation σ=A/√Texp[−B/(T−T0)]. Results are discussed on the basis of the properties of the ionically conducting liquid, filling the pores of the gels, and the influence of gel porosity (mainly pore size and interactions with the pore liquid) on the properties of the conducting medium.