Zn-Fe Double Hydroxide-Carbon Nanotube Anodes for Asymmetric Supercapacitors

Zn-Fe double hydroxide (Zn-Fe-DH) - multiwalled carbon nanotube (MWCNT) composite has been developed as a new material for energy storage in negative electrodes of asymmetric supercapacitors. A conceptually new approach is based on the use of celestine blue (CB) dye as a multifunctional additive. We discovered that CB acted as a co-dispersant for Zn-Fe-DH and MWCNT and facilitated their mixing. New strategy was based on the use of CB as charge transfer mediator, which facilitated charge-discharge reactions. The electrodes showed a capacitance of 5.2 F cm(-2) in 0.5 M Na2SO4 electrolyte in a voltage window of -1.0 to -0.2 V vs. saturated calomel electrode and good cyclic stability. A new asymmetric device has been developed, containing Zn-Fe-DH-MWCNT negative electrodes and polypyrrole coated MWCNT positive electrodes. Good capacitive behavior of cathode and anode materials was achieved at high active mass of 40 mg cm(-2) in partially overlapping potential windows. The device showed promising performance in a voltage window of 1.6 V. The capacitance of 2.2 F cm(-2) was obtained at a scan rate of 2 mV s(-1).