A novel intercalation cathode material for sodium-based batteries

• We propose NaFeZr2F11 and NaFeTi2F11 as novel sodium-based intercalation cathodes.
• The NaFeZr2F11 structure exists, and NaFeTi2F11 is a likely substitution material.
• The redox couple involved is Fe(2 +)/Fe(3 +).
• The computed average voltage of both structures is 4 V.

We propose NaFeZr2F11 and NaFeTi2F11 as novel materials for Na intercalation cathodes. The average sodium intercalation voltage for these compounds is about 4.0 V from first principles computations. The origin of this large voltage for a nominal Fe2 +/Fe3 + redox couple is proposed to be a combination of the fluorine “booster” effect, the inductive effect and the stiffness of the proposed structure upon desodiation.