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.