Hollow Hierarchical Carbon Spheres Decorated with Ultrathin Molybdenum Disulfide Nanosheets as High‐Capacity Electrode Materials for Asymmetric Supercapacitors

Abstract

A hierarchically structured nanocomposite consisting of ultrathin MoS2 nanosheets densely dispersed on the surface of hollow carbon spheres (MoS2@HCS) is prepared through a glucose‐assisted, one‐pot synthesis. When evaluated as the cathode material for supercapacitors, MoS2@HCS exhibits pseudocapacitive behavior in a KOH electrolyte. More importantly, the capacitive performance of MoS2@HCS can be further boosted by activating the composite electrode in a KOH solution. The activation process partially removes the carbonaceous materials covering the MoS2 surface, which leads to more exposure of active electrode materials to the electrolyte. Activated MoS2@HCS exhibits a high specific capacitance value of 458 F g−1 at 1 A g−1, which is approximately 2.5 times higher than that of the MoS2 electrode. Furthermore, MoS2@HCS exhibits remarkable cycling stability, with a capacitance retention of about 86% over 1000 cycles at 8 A g−1. To further demonstrate the practical applications of composite electrode, an asymmetric supercapacitor device (ASC) is fabricated by using activated MoS2@HCS and reduced graphene oxide as the positive and the negative electrodes, respectively. The fabricated device delivers a maximum energy density of 13.7 Wh kg−1 at a power density of 616 W kg−1. Even at a high power density of 4.9 kW kg−1, the ASC device can still retain 80% of the maximum energy density.

Ternary Composite Nanosheets with MoS2/WS2/Graphene Heterostructures as High‐Performance Cathode Materials for Supercapacitors

“…115 μA after 3 h. When self‐discharge behavior of the ASC device is taken into account, it is found that the cell voltage is gradually decreased from 1.5 to 0.36 V after 4 h, which corresponds to 24 % of the initial charged potential. The retention of output voltage is comparable to that for MoS 2 @HCS//rGO . These aforementioned results indicate that the rGO‐MoS 2 ‐WS 2 ‐4 can serve as one of the attractive electrode materials for supercapacitors.…”

“…The composite shows the weaker C1s signals at higher binding energy (>284.6 eV) than the as‐prepared GO nanosheets, suggesting that thermal annealing in H 2 removes most of oxygen‐containing functionalities. In the Mo 3d spectrum (Figure b), the major peaks at 232.2 and 229.0 eV are respectively assigned to Mo 3d 3/2 and Mo 3d 5/2 , which is resulted from the Mo 4+ ions . Moreover, the S 2p peak is observed at 226.1 eV, which confirms the existence of S species in MoS 2 .…”

“…Furthermore, the intercept of the EIS curve with the real impedance axis represents the equivalent series resistance ( R s ) while the diameter of the semicircle corresponds to charge transfer resistance ( R ct ) of the electrode material. These EIS spectra can be fitted using an equivalent circuit as shown in Figure S9 . It is found that R ct and R s values increase in the following order: rGO‐MoS 2 ‐WS 2 ‐4 ( R ct =0.13 Ω; R s =0.78 Ω ) < rGO‐MoS 2 ( R ct =1.32 Ω; R s = 0.89 Ω ) <rGO‐WS 2 ( R ct =19.3 Ω; R s = 0.91 Ω).…”

“…Prior to constructing the device, the ideal mass ratio of the rGO‐MoS 2 ‐WS 2 to rGO was determined through the following equation to maintain the charge balance between two electrodes [Eq. ] …”

A 3D Carbon Foam Derived from Phenol Resin via CsCl Soft‐Templating Approach for High‐Performance Supercapacitor

“…Carbon materials, such as activated carbon, graphene, carbon nanotubes, porous carbon, and so on, are frequently used as active component in EDLC because of the superior chemical stability, facile preparation, and adjustable structure. Valid specific surface area, appropriate pore size distribution matching ion sizes of electrolyte, and good electrical conductivity are indispensable for improving charge storage ability of EDLC .…”