Core–shell structured WS2@Ni-Co-S composite and activated carbon derived from rose flowers as high-efficiency hybrid supercapacitor electrodes

Abstract

Developing highly efficient nanomaterials for energy storage in hybrid supercapacitors is important, but remains challenging. Herein, a MOFs-encapsulated-polyoxometalate (POM)-template strategy followed vulcanization was employed for preparing core-shell structure WS2@Ni-Co-S-X electrode materials. Effect of Ni and Co mass ratio on the morphology and electrochemical properties of the resulted composites were systematically studied. The core-shell structure exposed more active sites for fast Faradaic reactions and ensured the high utilization of electrode materials. Meanwhile, the synergistic effect between the two components effectively improved the electrochemical performance of the composite. It was found that the obtained battery-type WS2@Ni-Co-S-1 electrode material had a high specific capacitance of 1920.3 F·g−1 at 1 A·g−1 and a good rate performance with a specific capacitance retension of 72.84 % at 10 A·g−1 as well as an excellent cycle stability with only 6.25 % decrease of specific capacitance after 20,000 cycles. Biomass carbon with layered porous structure was prepared by activating rose with a convenient salt sealing technology, which also showed good electrochemical performance. Using this carbon as the negative electrode and WS2@Ni-Co-S-1 as the positive electrode, the assembled hybrid supercapacitor device achieved a high potential window of 1.7 V and a relatively high energy density, and could also light a small red bulb for a few seconds. This indicates that the device has broad application prospects in high-performance energy storage.