Interlayer Conducting Mechanism in α-LiAlO₂ Enables Fast Proton Transport with Low Activation Energy for Solid Oxide Fuel Cells

Abstract

The α-NaFeO2 structure-type oxides, such as LiNiO2, LiCoO2, and α-LiAlO2, could not only provide channels for Li+ conduction but also conduct protons through intercalation. However, the detailed conduction mechanism of protons in the layer structure oxide needs to be further distinguished. In this work, we prepared layered-oxide α-Li0.88AlO2 and used it as an electrolyte to assemble a solid oxide fuel cell (SOFC), which delivered an output of 1046 mW cm–2 at 550 °C, a decent power output is ascribed to the excellent ion conductivity (0.2 S cm–1) and low activation energy (0.36 eV) of the α-Li0.88AlO2 electrolyte. Moreover, the H/D isotope experiments revealed that the proton dominated the ion conduction of α-Li0.88AlO2. First-principles calculations indicate that the special structure-layered oxides provide channels that allow protons to transfer rapidly with low activation energy. This work indicates the possibility of using layered oxides as proton conductors in a low-temperature SOFC (LT-SOFC) and reveals the proton transport mechanism in oxides, it provides a new approach to exploit novel electrolytes for LT-SOFC.