Defects, Dopants and Sodium Mobility in Na₂MnSiO₄.

ABSTRACT: Sodium manganese orthosilicate, Na₂MnSiO₄, is a promising positive electrode material in rechargeable sodium ion batteries. Atomistic scale simulations are used to study the defects, doping behaviour and sodium migration paths in Na₂MnSiO₄. The most favourable intrinsic defect type is the cation anti-site (0.44?eV/defect), in which, Na and Mn exchange their positions. The second most favourable defect energy process is found to be the Na Frenkel (1.60?eV/defect) indicating that Na diffusion is assisted by the formation of Na vacancies via the vacancy mechanism. Long range sodium paths via vacancy mechanism were constructed and it is confirmed that the lowest activation energy (0.81?eV) migration path is three dimensional with zig-zag pattern. Subvalent doping by Al on the Si site is energetically favourable suggesting that this defect engineering stratergy to increase the Na content in Na₂MnSiO₄ warrants experimental verification.

SUBMITTER: Kuganathan N 

PROVIDER: S-EPMC6168608 | biostudies-literature | 2018 Oct

REPOSITORIES: biostudies-literature