Metallic MoS2 nanosphere electrode for aqueous symmetric supercapacitors with high energy and power densities

Metallic 1T-MoS2 nanospheres composed of nanosheets were facilely synthesized by a hydrothermal method, and the moderate polyvinyl alcohol (PVA) and K+ ions were intentionally introduced in the subsequent exfoliation process. The as-prepared electrode (1T-MoS2/PVAK+), collected on the available carbon paper through vacuum filtration, exhibits a large specific capacitance of 488 F g−1 at a current density of 1 A g−1 in an aqueous electrolyte (3M KCl) because of the crosslink effect PVA to integrate the MoS2 nanospheres and interaction of K+ cation into the interlayers of MoS2. An aqueous symmetric supercapacitor was further prepared with 1T-MoS2/PVAK+ as the positive and negative electrodes. 1T-MoS2/PVAK+//1T-MoS2/PVAK+ device can work with an operating voltage of 1.6 V and manifests a high energy density of 49.0 Wh kg−1 at power density of 800 W kg−1. Remarkably, the maximum power density of 1T-MoS2/PVAK+//1T-MoS2/PVAK+ device reaches as high as 8000 W kg−1 with a corresponding energy density of 38.2 Wh kg−1. Furthermore, this type of aqueous symmetric device evidences the outstanding cycling stability with capacitance retention of 96% after 16,000 charge–discharge cycles at 1 A g−1. These excellent electrochemical performances of 1T-MoS2/PVAK+ electrode demonstrate a promising potential for application in supercapacitor with high energy density and high power density.