Next Article in Journal
Elastic Mechanical Properties of 45S5-Based Bioactive Glass–Ceramic Scaffolds
Previous Article in Journal
Impact of the Morphology of Micro- and Nanosized Powder Mixtures on the Microstructure of Mg-Mg2Si-CNT Composite Sinters
Open AccessArticle

Defect Chemistry, Sodium Diffusion and Doping Behaviour in NaFeO2 Polymorphs as Cathode Materials for Na-Ion Batteries: A Computational Study

1
Department of Materials, Imperial College London, London SW7 2AZ, UK
2
Faculty of Engineering, Environment and Computing, Coventry University, Priory Street, Coventry CV1 5FB, UK
*
Author to whom correspondence should be addressed.
Materials 2019, 12(19), 3243; https://doi.org/10.3390/ma12193243
Received: 10 September 2019 / Revised: 26 September 2019 / Accepted: 2 October 2019 / Published: 4 October 2019
Minor metal-free sodium iron dioxide, NaFeO2, is a promising cathode material in sodium-ion batteries. Computational simulations based on the classical potentials were used to study the defects, sodium diffusion paths and cation doping behaviour in the α- and β-NaFeO2 polymorphs. The present simulations show good reproduction of both α- and β-NaFeO2. The most thermodynamically favourable defect is Na Frenkel, whereas the second most favourable defect is the cation antisite, in which Na and Fe exchange their positions. The migration energies suggest that there is a very small difference in intrinsic Na mobility between the two polymorphs but their migration paths are completely different. A variety of aliovalent and isovalent dopants were examined. Subvalent doping by Co and Zn on the Fe site is calculated to be energetically favourable in α- and β-NaFeO2, respectively, suggesting the interstitial Na concentration can be increased by using this defect engineering strategy. Conversely, doping by Ge on Fe in α-NaFeO2 and Si (or Ge) on Fe in β-NaFeO2 is energetically favourable to introduce a high concentration of Na vacancies that act as vehicles for the vacancy-assisted Na diffusion in NaFeO2. Electronic structure calculations by using density functional theory (DFT) reveal that favourable dopants lead to a reduction in the band gap. View Full-Text
Keywords: NaFeO2; defects; Na-ion diffusion; dopants; atomistic simulation NaFeO2; defects; Na-ion diffusion; dopants; atomistic simulation
Show Figures

Graphical abstract

MDPI and ACS Style

Kuganathan, N.; Kelaidis, N.; Chroneos, A. Defect Chemistry, Sodium Diffusion and Doping Behaviour in NaFeO2 Polymorphs as Cathode Materials for Na-Ion Batteries: A Computational Study. Materials 2019, 12, 3243.

Show more citation formats Show less citations formats
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

1
Back to TopTop