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 O^2? 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.