Defect and Dopant Properties and Na‐Ion Mobility in the Na₂MnO₃ Cathode Material

Na₂MnO₃ is a promising candidate for sodium‐based oxide battery systems due to its structural characteristics and ionic conductivity. Atomistic simulation are used to analyze sodium‐ion diffusion pathways and intrinsic defect properties. The reliability of the interatomic potentials is confirmed by accurately reproducing key mechanical properties, including elastic constants, shear modulus, Young's modulus, bulk modulus, and Poisson's ratio, which reveals strong mechanical anisotropy. Among intrinsic defects, the sodium Frenkel defect is found to be the most energetically favorable, creating sodium vacancies that promote diffusion. The Na₂O Schottky defect is identified as the second most favorable. The low activation energy for Na⁺ migration (0.49 eV) indicates high ionic conductivity. Furthermore, doping Mn⁴⁺ sites with trivalent cations (R³⁺ = Al, Cr, Ga, Fe, Y, and Sc, La) enhances Na⁺ concentration by generating additional charge carriers. The local structural distortion induced by these dopants is thoroughly examined and found to potentially improve electrochemical performance. These findings suggest that trivalent doping is an effective strategy to enhance Na‐ion mobility and battery efficiency, highlighting Na₂MnO₃ as a strong candidate for high‐performance sodium‐ion energy storage devices.