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

A novel combination reaction of Na2Fe(SO4)2·nH2O (n = 2,4) and FeSO4·H2O to form Na2+2δFe2 −δ(SO4)3 (NFS) cathode is revealed, which delivers a discharging capacity of 95.9 mAh g−1 at 0.05 C and 60 mAh g−1 at 10 C. The full NFS@C@2%CNTs//HC cell, with an operating voltage of 3.5 V and mass-energy density of 140 Wh kg−1, is promising for large-scale commercialization. AbstractIron-based sulfate cathodes of alluaudite Na2+2δFe2 −δ(SO4)3 (NFS) in sodium-ion batteries with low cost, steady cycling performance, and high voltage are promising for grid-scale energy storage systems. However, the poor electronic conductivity and the limited understanding of the phase-evolution of precursors hinder obtaining high-rate capacity and the pure phase. Distinctive NFS@C@n%CNTs (n = 1, 2, 5, 10) sphere-shell conductive networks composite cathode materials are constructed creatively, which exhibit superior reversible capacity and rate performance. In detail, the designed NFS@C@2%CNTs cathode delivers an initial discharge capacity of 95.9 mAh g−1 at 0.05 C and up to 60 mAh g−1 at a high rate of 10 C. The full NFS@C@2%CNTs//HC cell delivers a practical operating voltage of 3.5  V and mass-energy density of 140 Wh kg−1 at 0.1 C, and it can also retain 67.37 mAh g−1 with a capacity retention rate of 96.4% after 200 cycles at 2 C. On the other hand, a novel combination reaction mechanism is first revealed for forming NFS from the mixtures of Na2Fe(SO4)2·nH2O (n = 2, 4) an...

Source: Small - September 21, 2023 Category: Nanotechnology Authors: Wei Yang, Qi Liu, Lijuan Hou, Qiang Yang, Daobin Mu, Guoqiang Tan, Li Li, Renjie Chen, Feng Wu Tags: Research Article Source Type: research