Metallic MoS2 nanosphere electrode for aqueous symmetric supercapacitors with high energy and power densities
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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.
The authors gratefully acknowledge support from the National Nature Science Foundation of China (61674059), the Science and Technology Planning Project of Guangdong Province (2015A010103012, 2015B010132009), the Science and Technology Planning Project of Guangzhou City (201804010399), and the Innovative Project of Education Department of Guangdong Province (2017KTSCX050).