Defect Formation and Diffusion on the (001) Surface of LiKCO3 for Fuel Cell Applications: Insight from Hybrid DFT
Among promising applications, LiKCO3 can be used as component of the oxide carbonate electrolytes for low temperature solid oxide fuel cells (LT SOFCs) but the species ensuring the transport at the interface between the two phases is still undetermined. In view of better clarifying the role of the carbonate phase in these materials, we studied the dominant Li related diffusion carriers and their diffusion pathways on the LiKCO3 (001) surface by density functional theory (DFT) calculations, based on the hybrid functional PBE0 for the exchange and correlation terms. Among the four different defect types considered, VLi' was found to be the thermodynamically most stable defect in LiKCO3, but the dominant diffusion carrier was Lii+ with low diffusion barriers whose origin could be related to high O coordination and low electrostatic repulsion arguments. The effect of the voltage applied in SOFC devices on diffusion paths was also taken into account by performing calculations in the presence of an external e.