High Performance of Electrochemically Deposited NiCo2S4/CNT Composites on Nickel Foam in Flexible Asymmetric Supercapacitors

To exploit an efficient supercapacitor, improving the comprehensive properties of electrode materials has become an important goal. In this work, NiCo2S4 nanosheets were successfully combined with highly conductive carboxylated carbon nanotubes (CNT-h-COOH) by electrochemical deposition, forming an interconnected porous network of NiCo2S4 nanosheets/CNT composite on the nickel foam. The results showed that the deposition potential and time played important roles to influence the morphology and electrochemical performance of NiCo2S4 nanosheets/CNT composite. It turned out that the NiCo2S4/CNT composite prepared by depositing at a −0.9 V for 10 min presented excellent specific capacity at 1 A g–1 (2498.12 F g–1), outstanding rate characteristic at 100 A g–1 (compared with 1 A g–1, the capacitance retention was 61.1%), and exceptional cycle performance at 20 A g–1 (the capacitance retention rate after 10 000 charge/discharge cycles was 96.08%). Further, the flexible asymmetric supercapacitor (ASC) with a poly(vinyl alcohol) (PVA)/KOH gel electrolyte was obtained using commercial activated carbon as the anode and the NiCo2S4/CNT composite as the cathode. The ASC showed a high specific capacity of 215.06 F g–1 at 0.25 A g–1, an exceptional capacitance retention rate of 89.03% after 10 000 cycles, an outstanding energy density of 76.47 Wh kg–1 at 201.01 W kg–1, and excellent flexibility. Thereby, our study demonstrated that the electrodeposited porous NiCo2S4/CNT composite possesses a broad potential application in the area of supercapacitors.