High Ionic Conductivity in a LiFeO2–LiAlO2 Composite Under H2/Air Fuel Cell Conditions

New ionic conducting materials for electrolytes for electrochemical devices have been attracting the interest of researchers in energy materials. Here, for the first time, we report a conductive composite with high ionic conductivity derived from an electronic conductor α-LiFeO2 and an insulator γ-LiAlO2. High conductivity was observed in the α-LiFeO2–γ-LiAlO2 composite when prepared by a solid state reaction method. However, the conductivity enhancement in α-LiFeO2–γ-LiAlO2 composite was not observed when the two oxides were mechanically mixed. The α-LiFeO2–γ-LiAlO2 composite also exhibits O2− or/and H+ ionic conduction which was confirmed through H2/air fuel cell measurements. An exceptionally high conductivity of 0.50 S cm−1 at 650 °C was observed under H2/air fuel cell conditions. This provides a new approach to discover novel ionic conductors from composite materials derived from electronic conductors.