Carbon/two-dimensional MoTe₂core/shell-structured microspheres as an anode material for Na-ion batteries

Abstract

Unique-structured composite microspheres of carbon and MoTe were prepared by a two-step process. Precursor C-MoO composite microspheres were prepared by spray pyrolysis, and then the precursor was transformed into C-MoTe composite microspheres by a tellurization process. C-MoTe composites with a uniform distribution of MoTe nanocrystals (C/MoTe) and core-shell-structured C-MoTe composites (C@MoTe) were synthesized at tellurization temperatures of 450 and 600 °C, respectively. At a higher tellurization temperature of 600 °C, all of the MoTe nanocrystals moved to the surface of the microsphere because of the Ostwald ripening process. The initial discharge capacities of the C/MoTe, C@MoTe, and bare MoTe (i.e., containing no carbonaceous materials) powders for Na-ion storage at a current density of 1.0 A g were 328, 388, and 341 mA h g, respectively. The discharge capacities of the C/MoTe, C@MoTe, and bare MoTe powders for the 200 cycle were 241, 286, and 104 mA h g, respectively, and the corresponding capacity retentions, which were measured from the second cycle were 100%, 99%, and 37%, respectively. The high structural stability and well-developed two-dimensional layer of MoTe of the C@MoTe microspheres provide superior Na-ion storage properties compared to those of the C/MoTe microspheres and bare MoTe powder.

Highly Active, Durable Ultrathin MoTe2 Layers for the Electroreduction of CO2 to CH4

“…Weak peaks were observed at 232.9 and 236.0 eV, corresponding to MoO bonds. Te 3d 5/2 and Te 3d 3/2 peaks were observed at 573.5 and 583.8 eV, respectively, corresponding to the MoTe bonds in 2H‐MoTe 2 (Figure c). Small peaks were observed at 576.6 and 587.0 eV, corresponding to the TeO impurity.…”

“…XPS was utilized to further confirm the electronic states and bonding types of molybdenum and tellurium in the ultrathin MoTe 2 layers. In the high‐resolution Mo 3d and Te 3d spectra, Mo3d 5/2 and Mo 3d 3/2 peaks were observed at 228.8 and 231.8 eV, respectively, corresponding to the MoTe bonds in 2H‐MoTe 2 (Figure b). Weak peaks were observed at 232.9 and 236.0 eV, corresponding to MoO bonds.…”

Hierarchical Metal Sulfide/Carbon Spheres: A Generalized Synthesis and High Sodium‐Storage Performance

“…In addition, a hollow structured V 2 S 3 can be confirmed, which might be caused by Ostwald ripening effect. [27,28] The hierarchical V 2 S 3 &C spheres provide a very effective mixed-conducting network together with the greatly reduced sodium diffusion length within the particles, which is expected to alleviate the problems associated with conversion reactions.…”

Hierarchical Metal Sulfide/Carbon Spheres: A Generalized Synthesis and High Sodium‐Storage Performance

“…Elemental mapping analysis based on energy‐dispersive X‐ray spectroscopy (EDX) demonstrates uniform distribution of carbon‐coating layers on/in V 2 S 3 spheres (Figure j), which in addition to suppressing of the particles’ growth also improves electric interconnectivity of the V 2 S 3 nanocrystals. In addition, a hollow structured V 2 S 3 can be confirmed, which might be caused by Ostwald ripening effect . The hierarchical V 2 S 3 ⊂C spheres provide a very effective mixed‐conducting network together with the greatly reduced sodium diffusion length within the particles, which is expected to alleviate the problems associated with conversion reactions.…”