Chalcogen effects and cathodic properties of scandium-based materials for sodium-ion batteries

Sodium-ion batteries emerged as a sustainable alternative to overcome the cost, availability, safety, and energy density concerns challenged by existing commercialized lithium-ion battery technology. This paper focuses on modeling new layered sodium scandium chalcogenides (O, S, and Se), prepared by the solid-state synthesis method as electrode materials for large-scale energy storage. We examined and compared the structural, electronic, cathodic, and transport properties of NaScX₂ layered materials. We continued our investigation into the stability of these cathode materials for the charge–discharge process. Among the chalcogenide materials, NaScSe₂ exhibited the lowest estimated energy barrier for Na-ion diffusion, with values of 0.57 eV via a single vacancy mechanism and 0.21 eV for a divacancy mechanism. As we go to the higher ionic radii of divalent anions, it shows higher electric polarizability. Hence, layered selenide has a higher capability to deform the electron charge density of anion by the nearby Na cations. This influences the mobility of diffusing alkali metal cations.