| Abstract Scope |
Defect chemistry in Ruddlesden–Popper nickelates (Ln₂NiO₄+δ) significantly impacts their mixed ionic–electronic conduction properties, crucial for solid oxide fuel cell (SOFC) cathode performance. Using La₂NiO₄+δ as a case study, we investigate atomic-scale mechanisms governing oxygen interstitial (O_i″) formation and hole conduction through density functional theory (DFT), phonon calculations, Zentropy theory, and Boltzmann transport equations. Our analysis highlights the dominance of O_i″ defects in oxidizing conditions, showing that interstitial formation energies decrease systematically from La to Pr due to lanthanide ionic radius contraction. Predicted electronic conductivities align closely with experimental data, validating our computational approach. Key findings underscore the necessity of incorporating temperature-dependent defect energetics and entropic stabilization in modeling. These insights establish a framework for optimizing cathode materials through controlled doping and non-stoichiometry, paving the way toward enhanced SOFC performance and durability. |