The target material was synthesized by reacting 1.54 g Na2SO4 (Wako, 99%) and 2.73 g FeSO4. The anhydrous FeSO4 precursor was prepared in-house by annealing commercial FeSO4.7H2O Na2Fe2(SO4)3 cathode compound was obtained via classical solid-state synthesis by ball milling the precursors for 4 h followed by annealing the mixture at 350 degC for 24 h under steady Ar flow. Chemical oxidation was performed to obtain desodiated Na2-xFe2(SO4)3 samples using NO2BF4 (Alfa Aesar, 96%) oxidant dissolved in acetonitrile solvent (Wako, H2O level <5 p.p.m.). The solution was stirred overnight (with steady Ar flow), and the final products were filtered and dried at 60 degC under vacuum.
Na2SO4
reacting
1.54 g
g
Na2SO4
99%
%
FeSO4
reacting
2.73 g
g
precursors
ball milling
4 h
h
mixture
annealing
350 degC
degC
mixture
annealing
24 h
h
NO2BF4
96%
%
acetonitrile solvent
H2O level
<5 p.p.m.
p.p.m.
final products
dried
60 degC
degC