Interface engineering of Fe3Se4/FeSe heterostructure encapsulated in electrospun carbon nanofibers for fast and robust sodium storage

Bilateral Interfaces in In2Se3-CoIn2-CoSe2 Heterostructures for High-Rate Reversible Sodium Storage

“…From the XRD patterns (Figure S11), the characteristic peaks of In 2 Se 3 and CoSe 2 could be observed at the beginning of discharge process. Subsequently, the peak intensities gradually weakened and finally disappeared at 1.2 V, suggesting that both selenides have been converted into Na 2 Se, which is confirmed by the appearance of the two characteristic peaks at 22.5° and 37.3° of Na 2 Se . When fully discharged to 0 V, the peaks of Na 2 Se can still be observed, and two new peaks appearing at 33° and 43.7° could be indexed to InNa alloy and Co, respectively.…”

“…The slight, but noticeable, increase in capacity during the first 20 cycles can be related to the activation process of the active materials. 25,44,45 Apparently, In 2 Se 3 /CoSe 2 -400 shows a capacity of 370.2 mAh g −1 after 200 cycles, which is lower than that of In 2 Se 3 /CoSe 2 -450 but higher than that of pure In 2 Se 3 (290.6 mAh g −1 ) and CoSe 2 (197.3 mAh g −1 ). Post-mortem SEM measurement was carried out to confirm the integrity of the structure (Figure S9).…”

“…Subsequently, the peak intensities gradually weakened and finally disappeared at 1.2 V, suggesting that both selenides have been converted into Na 2 Se, which is confirmed by the appearance of the two characteristic peaks at 22.5°and 37.3°o f Na 2 Se. 45 When fully discharged to 0 V, the peaks of Na 2 Se can still be observed, and two new peaks appearing at 33°and 43.7°could be indexed to InNa alloy and Co, respectively. The peaks of Na 2 Se disappeared after charging to 2.0 V. Notably, when charged to 2.5 V, no obvious peak of In 2 Se 3 and CoSe 2 could be observed, indicating the poor crystallinity of these formed metal selenides after the sodiation/desodiation process.…”

Carbon-Coated Three-Dimensional MXene/Iron Selenide Ball with Core–Shell Structure for High-Performance Potassium-Ion Batteries

“…7 a–d). In the first cathodic sweep, FeSe x @C/MB exhibited broad three peaks, in which the peak observed at 2.27 V was associated with the intercalation of K + into MB [ 15 ], and peaks at 1.18 and 0.45 V corresponded to the intercalation of K + into FeSe x and the formation of metal Fe and K 2 Se from K x FeSe y , respectively [ 51 , 52 ]. In addition, during the subsequent cathodic sweeps, the initial peaks disappeared, and new peaks appeared at a higher potential with low intensity.…”

Magnetism of Tetragonal β-Fe3Se4 Nanoplates Controllably Synthesized by Thermal Decomposition of (β-Fe2Se3)4[Fe(tepa)] Hybrid

“…According to the fitting area for the Fe 2+ and Fe 3+ ions, the molar ratio of Fe 2+ /Fe 3+ in the as-synthetic β-Fe 3 Se 4 nanoplates was estimated to be 1:1.9, which is close to the Fe 2+ /Fe 3+ of 1:2 for β-Fe 3 Se 4 based on the electrical neutrality principles. Figure 5c shows the Se 3d peak at 55.1 eV, indicating the presence of Se-Fe-Se [24,25], which could be deconvoluted into Se 3d 5/2 at 54.7 eV and Se 3d 3/2 at 55.6 eV. For the β-Fe 3 Se 4 nanoplates annealed at 623 K, the C 1s (at 285 and 285.5 eV), Fe 2p with Fe 2+ (2p 3/2 at 710.2 eV, 2p 1/2 at 723.8 eV) and Fe 3+ (2p 3/2 at 711.8 eV and 2p 1/2 at 725.4 eV) and Se 3d (3d 5/2 at 55.1 eV and 3d 3/2 at 56.0 eV) spectra were also analyzed and presented in Figure 5d-f, which are similar to the results of the as-synthetic β-Fe 3 Se 4 nanoplates.…”