Properties of LiI—Alumina composite electrolytes

LiI and 14 different LiI — high surface area Al 2 O 3 composite electrolyte materials have been examined by the ac-admittance method. The presented data span the temperature range from 25°C to 300°C, and the composition range from 20 to 70 mole % Al 2 O 3 , respectively. Maxima are observed in the isothermal conductivity versus composition plots at 40–50 mole % Al 2 O 3 . At 25°C the best material has a specific conductivity equal to3.75·10 −5 S/cm, or a factor 100 to 1000 higher than for LiI at the same temperature. The enhanced conductivity results from an increase in the preexponential factors and a minimum in the overall activation energy for conduction occuring between 40 and 50 mole % alumina. The compositional dependence of the conductivity is discussed on basis of a pore-model. Preliminary analysis of Hebb-Wagner polarization data for the cell Li/LiI/C indicates that electronic leakage currents in LiI are carried by electrons.