Abstract:
Abstract: Sodium nickelate, NaNiO2, is a candidate cathode material for sodium ion batteries due
to its high volumetric and gravimetric energy density. The use of atomistic simulation techniques
allows the examination of the defect energetics, Na-ion diffusion and dopant properties within the
crystal. Here, we show that the lowest energy intrinsic defect process is the Na-Ni anti-site. The Na
Frenkel, which introduces Na vacancies in the lattice, is found to be the second most favourable defect
process and this process is higher in energy only by 0.16 eV than the anti-site defect. Favourable
Na-ion diffusion barrier of 0.67 eV in the ab plane indicates that the Na-ion diffusion in this material is
relatively fast. Favourable divalent dopant on the Ni site is Co2+ that increases additional Na, leading
to high capacity. The formation of Na vacancies can be facilitated by doping Ti4+ on the Ni site. The
promising isovalent dopant on the Ni site is Ga3+.
