Ni3S2@polypyrrole composite supported on nickel foam with improved rate capability and cycling durability for asymmetric supercapacitor device applications

Ni 3 S 2 @polypyrrole/nickel foam (Ni 3 S 2 @PPy/NF) composite was successfully synthesized by combining a facile hydrothermal synthesis and a simple electrochemical-deposited process. For comparative study, the honeycomb-shaped Ni 3 S 2 had in situ been grown on NF without the addition of any nickel salt to obtain the Ni 3 S 2 /NF composite. The electrochemical measurement results show that the area capacitance of the Ni 3 S 2 @PPy/NF electrode is 1.13 F cm −2 that is slightly lower than 1.26 F cm −2 of the Ni 3 S 2 /NF electrode at a high current density of 30 mA cm −2 , yet its rate capability and cycling stability are far better than those of the Ni 3 S 2 /NF electrode. Meanwhile, an asymmetric supercapacitor on the basis of the Ni 3 S 2 @PPy/NF anode and the AC cathode exhibits a high energy density and power density of 17.54 Wh kg −1 and 179.33 W kg −1 at 2.5 mA cm −2 , respectively; besides, the energy density is still 8.67 Wh kg −1 at a power density of 3587.41 W kg −1 even at 50 mA cm −2 . Moreover, the capacitances of the device remain unchanged after 3000 galvanostatic charge/discharge cycles at a high current density of 30 mA cm −2 . Furthermore, two such 1 cm 2 devices connected in series can light five 40-mW LED indicators or power one of the same-power LED indicator for 20 min after being fully charged. The results demonstrate that our asymmetric supercapacitor has a promising potential in commercial applications.