Metal organic framework derived P-doping CoS@C with sulfide defect to boost high-performance asymmetric supercapacitors.

Cobalt sulfide (CoS) is a promising battery-type material for electrochemical energy storage. However, the poor conductivity and slow charge transfer kinetics as well as the deficiency of electrochemically active sites seriously limit their applications. Herein, a class of the P-doping induced hexagonal CoS nanosheets with S defects (P-CoS1-x) derived from Co-based metal organic frameworks (MOFs) supported on carbon nanotube film (CNT) is designed and prepared. The density functional theory (DFT) simulations show the higher conductivity of the P-CoS1-x electrode than CoS. Taking advantage of the synergistic effects of the high conductive P-CoS nanosheets with rich S defects and the flexible CNT, the P-CoS1-x/CNT electrode exhibits a high reversible capacity of 4.3F cm-2, remarkable rate capability, and outstanding long-term cyclability. Impressively, the flexible asymmetric supercapacitor (ASC) based on P-CoS1-x//CoS@PPy achieves a satisfying energy density of 0.18 mWh cm-2 and high bending stability. The electrocatalytic result suggests that the P-CoS1-x possesses the lowest overpotential and the smallest Tafel slope. This vacancy engineering strategy also provides a new insight into active materials and should be beneficial for the design of the next generation of energy storage devices.