Sodium iron sulfate alluaudite solid solution for Na-ion batteries: moving towards stoichiometric Na₂Fe₂(SO₄)₃

Abstract

The elusive Na2Fe2(SO4)3 stoichiometric compound was obtained through a precipitation method and is electrochemically active as a cathode.

Spherical Shell with CNTs Network Structuring Fe‐Based Alluaudite Na2+2δFe2−δ(SO4)3 Cathode and Novel Phase Transition Mechanism for Sodium‐Ion Battery

“…Owing to the higher working voltage of 3.8 V, the prepared material in the present work still exhibited a decent energy density close to 360 Wh kg −1 , which is relatively higher than other reported materials (Figure 7i and Table S7, Supporting Information). [17][18][22][23][24]32,36] On the other hand, both NFS@C and NFS@C@2% CNTs showed an irreversible capacity loss in the initial charging process, as shown in Figure 8a and Figure S9, Supporting Information, which is the same as the previous reports. [9,10,40] Two anodic peaks at 3.67 and 4.12 V existed in discharging and three corresponding reduction peaks occurred in the first charging process by CV test, and it displayed three pairs of reversible redox peaks in the second and third cycles (Figure 8b and Figure S9, Supporting Information).…”

Progress on Fe‐Based Polyanionic Oxide Cathodes Materials toward Grid‐Scale Energy Storage for Sodium‐Ion Batteries

“…Additionally, the heat treatment would disintegrate the metastable stoichiometric phase into sodium‐rich phase Na 2.56 Fe 1.75 (SO 4 ) 3 and secondary phase FeSO 4 due to the repulsive force caused by intimate contact between Fe 2+ in the Fe 2 O 10 dimer. [ 143 ] A novel aqueous solution method to synthesize high‐purity stoichiometric Na 2 Fe 2 (SO 4 ) 3 /C has also been reported (Figure 5g), which exhibited the initial discharge capacity of 110 mAh g –1 at 0.1 C and remained the capacity above 90% after 50 cycles at 0.1 C. [ 144 ] However, excess sodium should be added, and the prepared nanoparticles tended to agglomerate. Besides, Li et al.…”

A comprehensive review on recent advances of polyanionic cathode materials in Na‐ion batteries for cost effective energy storage applications

“…as well as exhibits antiferromagnetic ordering below 10.2 K (Dwibedi et al, 2017). Jungers et al shows an initial reversible discharge capacity of 102 mAh/g at C/20 for Na 2 Fe 2 (SO 4 ) 3 and the capacity retention shows good reversibility up to 20 C over 30 cycles (Jungers et al, 2019). However, Fe-based sulfates undergo severe difficulties like unstable sulfate radicals above 450 C, hygroscopicity of sulfate units resulting in poor electrochemical activity and irreversible capacity loss.…”