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 MoS 2 nanosheets densely dispersed on the surface of hollow carbon spheres (MoS 2 @HCS) is prepared through a glucose‐assisted, one‐pot synthesis. When evaluated as the cathode material for supercapacitors, MoS 2 @HCS exhibits pseudocapacitive behavior in a KOH electrolyte. More importantly, the capacitive performance of MoS 2 @HCS can be further boosted by activating the composite electrode in a KOH solution. The activation process partially removes the carbonaceous materials covering the MoS 2 surface, which leads to more exposure of active electrode materials to the electrolyte. Activated MoS 2 @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 MoS 2 electrode. Furthermore, MoS 2 @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 MoS 2 @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.