Ingeniously Designed Yolk–Shell-Structured FeSe₂@NDC Nanoboxes as an Excellent Long-Life and High-Rate Anode for Half/Full Na-Ion Batteries

Abstract

Thanks to their high conductivity and theoretical capacity, transition metal selenides have demanded significant research attention as prospective anodes for sodium-ion batteries. Nevertheless, their practical applications are hindered by finite cycle life and inferior rate performance because of large volume expansion, polyselenide dissolution, and sluggish dynamics. Herein, the nitrogen-doped carbon (NC)-coated FeSe2 nanoparticles encapsulated in NC nanoboxes (termed FeSe2@NDC NBs) are fabricated through the facile thermal selenization of polydopamine-wrapped Prussian blue precursors. In this composite, the existing nitrogen-doped dual carbon layer improves the intrinsic conductivity and structural integrity, while the unique porous yolk–shell architecture significantly mitigates the volume swelling during the sodium/desodium process. Moreover, the derived Fe–N–C bonds can effectively capture polyselenide, as well as promote Na+ transportation and good reversible conversion reaction. As expected, the FeSe2@NDC NBs deliver remarkable rate performance (374.9 mA h g–1 at 10.0 A g–1) and long-cycling stability (403.3 mA h g–1 over 2000 loops at 5.0 A g–1). When further coupled with a self-made Na3V2(PO4)3@C cathode in sodium-ion full cells, FeSe2@NDC NBs also exhibit considerably high and stable sodium-storage performance.

Revealing the Reaction and Fading Mechanism of FeSe2 Cathodes for Rechargeable Magnesium Batteries

“…Satellite peaks are also observed at 711.6 and 724.5 eV. In the Se 3d spectrum (Figure 1c), the peaks at 54.5 and 55.4 eV are respectively ascribed to Se 3d 5/2 and Se 3d 3/2 , signifying the Fe−Se and Se−Se bonds [28–29] . Besides, the peak at 58.9 eV is from the surface oxidation, which is a common phenomenon for synthesized selenides.…”

“…In the Se 3d spectrum (Figure 1c), the peaks at 54.5 and 55.4 eV are respectively ascribed to Se 3d 5/2 and Se 3d 3/2 , signifying the FeÀ Se and SeÀ Se bonds. [28][29] Besides, the peak at 58.9 eV is from the surface oxidation, which is a common phenomenon for synthesized selenides. The crystal structure of FeSe 2 could be described by Figure 1d, in which Fe atoms are bonded with six Se atoms in an octahedral arrangement.…”

Self-assembled nanoflower-like FeSe2/MoSe2 heterojunction anode with enhanced kinetics for superior-performance Na-ion half/full batteries

“…In the first anodic process, the oxidation peak at about 1.52 V corresponds to the formation of FeSe, and the four oxide peaks centered at around 1.67, 1.79, 2.05, and 2.31 V are assigned to the generation of Na x FeSe 2 , Na x MoSe 2 , FeSe 2 , and MoSe 2 , respectively. 36,37 The CV curves of FMSe overlap well after the initial scan, thereby suggesting that the three-dimensional heterostructure material possessed a remarkable electrochemical reversibility. Fig.…”

“…In the first anodic process, the oxidation peak at about 1.52 V corresponds to the formation of FeSe, and the four oxide peaks centered at around 1.67, 1.79, 2.05, and 2.31 V are assigned to the generation of Na x FeSe 2 , Na x MoSe 2 , FeSe 2 , and MoSe 2 , respectively. 36,37…”

Phosphorus-Doped FeOF Nanoparticle-Based Cathodes for Lithium Storage

“…As the scan rate increases from 0.2 to 1 mV s −1 , the anodic peaks shift to the positive direction, the cathodic peak shifts to the opposite direction, and these peaks gradually broaden, which is due to the increase in polarization at a higher scanning speed. 50 The b-value can be derived by fitting the log(i)−log(v) plot (calculation details in the Supporting Information), and the value of b close to 0.5 represents a diffusion-controlled process, while b close to 1 indicates electrochemical dominance by pseudocapacitive behavior. 51 The b-value obtained by fitting is 0.54, which indicates that the kinetics of the P-F6 electrode is mainly controlled by ionic diffusion (Figure 6b).…”