View source for Solvothermal synthesis of Sn3N4 as a high capacity sodium-ion anode: theoretical and experimental study of its storage mechanism

This article describes recent efforts to develop Sn3N4 as a battery anode material for Na batteries.  
The article is very intriguing for several reasons, which I highlight here and discuss below:

1) The really high capacity of Sn3N4 for Na is amazing.

2) We propose the conversion of the material to SnNa shells with vastly depleted SnXN4NaY cores.  Using a comparable energy argument, we estimate we can get to (3/4) Sn4Na15 + 4NaN.  This effectively gives 15.25 Na for each Sn3N4 unit.

2) We consider the convex hull of Sn and N with Na.  The Nitrogen has a particularly interesting point, being an experimentally smade Na3N, which could not be found to lie on the Convex hull.  The reason for this is due to the choice of N2 as the reference chemical potential for Nitrogen.  In future, a more suitable reference for N needs to be found.

3) It shows the PBE and HSE generally agree for convex hulls. 

4) Generally smaller grains give higher capacity.  This is because the reaction is significantly more favourable at the surface so the smaller the grain the better.

The article can be accessed here:

https://ore.exeter.ac.uk/repository/handle/10871/123099