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

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.