Abstract:
Polyanionic silicate-based cathode materials have attracted considerable attention due to their intrinsic
structural stability, strong thermal and chemical resistance, and ability to achieve high operating voltages through the
inductive effects of polyanion groups. In this study, atomistic simulations were conducted to explore the energetics of
intrinsic point defect formation, Na-ion migration pathways, and dopant incorporation in Na2FeSiO4, providing key
insights into its viability as a cathode material for sodium-ion batteries (SIBs). Among the native defects, the Na Frenkel
pair exhibited the lowest formation energy, suggesting a natural preference for vacancy-mediated Na-ion migration. The
calculated migration energy barriers of 0.38 and 0.41 eV further support the material’s capability for efficient sodium-ion
transport. Doping analysis identified K, Zn, and Ge as the most favorable isovalent dopants at the Na, Fe, and Si sites,
respectively, while Ga showed a strong tendency to substitute at Fe sites and facilitate Na-vacancy formation.
Furthermore, Al substitution at the Si site was found to increase the overall sodium content in the lattice. The electronic
structure of these promising dopants was further investigated using density functional theory (DFT), offering deeper
insights into their influence on the electrochemical behavior of Na2FeSiO4.
