Supporting Information

Unveiling the thermodynamic and kinetic properties of Eldfellite, NaFe(SO4)2: toward a high-capacity and low-

cost cathode material

Amitava Banerjee*a, Rafael B. Araujo*a and Rajeev Ahujaa,b aCondensed Matter Theory Group, Department of Physics and Astronomy, Box 516, Uppsala

University, S-75120 Uppsala, Sweden. bApplied Materials Physics, Department of Materials and Engineering, Royal Institute of Technology

(KTH), S-100 44 Stockholm, Sweden.

a) b) c)

d) e)

f)

g) h) i)

Figure S1. The ground state structure of each composition of NaxFe(SO4)2 (x=0-2), obtaining from the global optimization process is shown here. a) Na0Fe(SO4)2, b) Na0.25Fe(SO4)2, c) Na0.5Fe(SO4)2, d) Na0.75Fe(SO4)2, e) Na1Fe(SO4)2, f) Na1.25Fe(SO4)2, g) Na1.5Fe(SO4)2, h) Na1.75Fe(SO4)2, and i) Na2Fe(SO4)2.

Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A.This journal is © The Royal Society of Chemistry 2016