Hierarchical MoSe₂yolk–shell microspheres with superior Na-ion storage properties

Abstract

Yolk-shell-structured MoSe₂ microspheres were prepared via a simple selenization process of MoO₃ microspheres. The yolk-shell-structured MoSe₂ and MoO₃ microspheres delivered initial discharge capacities of 527 and 465 mA h g(-1) in the voltage range of 0.001-3 V vs. Na/Na(+) at a current density of 0.2 A g(-1), respectively, and their discharge capacities after 50 cycles were 433 and 141 mA h g(-1), respectively. The yolk-shell-structured MoSe₂ microspheres also exhibited outstanding high rate capabilities. The hierarchical yolk-shell structure comprised of wrinkled nanosheets facilitated fast Na-ion and electron kinetics, and buffered the large volume changes encountered during cycling.

Constructing monodispersed MoSe2 anchored on graphene: a superior nanomaterial for sodium storage

“…4c, the MoSe2/rGO hybrid nanostructure electrode exhibits final discharge capacities of 423.4, 384.0, 328.3, 259.4 and 200.2 mA h g −1 at current densities of 0.5, 1, 2, 4, and 8 A g −1 , respectively. It should be noted that this reversibility performance was much better than the other previous reports on this material [16,17]. After 60 charge/discharge cycles at different current densities, the discharge capacity of the MoSe2/rGO electrode could still achieve 448.2 mA h g −1 at 0.5 A g −1 , indicating superior rate capability and resilience ability of the electrode.…”

“…The peak at 0.65 V is attributed to the sodium insertion to MoSe2 to form NaxMoSe2 while the next peak at 0.44 V is due to the reduction of Mo 4+ to Mo metal accompanied by the forming of Na2Se and the irreversible decomposition of the electrolytes [16,34]. During the anodic scan, we could see two oxidation peaks at 0.8 and 1.75 V and this phenomenon is due to the partial oxidation of Mo and Na2Se [17]. Meanwhile, after the first cycle, one peak at 1.4 V shows up, and the two peaks at 0.44 and 0.65 V in the first cathodic sweep disappear, which may result from the reversible reaction of Mo 4+ + 2Na2Se ↔ MoSe2 + 4Na + [16,35].…”

“…Over the past few years, great attention has been paid to molybdenum sulfide (MoS2) due to its high theoretical specific capacity and good cycling performance in sodium storage. However, as a close analogue to the layer structured MoS2, the electrochemical sodium storage performance of MoSe2 has been rarely investigated [16][17][18][19]. In addition, it is reported that MoSe2 has smaller band gap and larger inter-planar space compared with MoS2, suggesting its smaller structure resistance for intercalating and de-intercalating of Na ion from the layered MoSe2 structure when used as anode material for SIBs [20].…”

“…Transition metal dichalcogenides (TMDs) MX2 (M = Mo or W, X = S or Se) with the similar feature of layered structure to graphite have great potential as alternative anode materials for sodium ion energy storage [11][12][13][14][15][16][17][18]. In general, each layer of M atoms are sandwiched between two layers of hexagonally close-packed X atoms and the nearby X layers are connected by weak van der Waals interaction.…”

“…Ko et al [17] synthesized hierarchical MoSe2 yolk-shell microspheres via a facile selenization of MoO3 microspheres, which possessed a reversible sodium storage capacity of 433 mA h g −1 after 50 cycles at a current density of 0.2 A g −1 . Yang et al [18] prepared porous hollow carbon spheres decorated with MoSe2 nanosheets via a three-step process, which manifested a reversible sodium capacity of 580 mA h g −1 after 100 cycles at a current density of 0.2 A g −1 .…”