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

Ni3S2@polypyrrole/nickel foam (Ni3S2@PPy/NF) composite was successfully synthesized by combining a facile hydrothermal synthesis and a simple electrochemical-deposited process. For comparative study, the honeycomb-shaped Ni3S2 had in situ been grown on NF without the addition of any nickel salt to obtain the Ni3S2/NF composite. The electrochemical measurement results show that the area capacitance of the Ni3S2@PPy/NF electrode is 1.13 F cm(-2) that is slightly lower than 1.26 F cm(-2) of the Ni3S2/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 Ni3S2/NF electrode. Meanwhile, an asymmetric supercapacitor on the basis of the Ni3S2@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.