Abstract
Zn-Fe double hydroxide (Zn-Fe-DH) – multiwalled carbon nanotube (MWCNT) composite has been developed 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 dispersant for Zn-Fe-DH and MWCNT, facilitated their mixing and interfacial charge transfer. The electrodes showed a capacitance of 5.2 F cm-2 in 0.5 M Na2SO4 electrolyte in a voltage window of -1.0 - -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 behaviour 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.
Highlights
Transition metal-based materials have generated significant interest for applications in energy generation and storage devices (Cheong and Zhitomirsky, 2009; Zhai et al, 2018; Cesano et al, 2019; Chen et al, 2019; Dong et al, 2019)
The polyaromatic structure of celestine blue (CB) was beneficial for its adsorption on multiwalled carbon nanotube (MWCNT), which involved π-π interactions (Ata et al, 2018)
It was hypothesized that CB can potentially improve mixing of MWCNT and Zn-Fe-DH because CB, adsorbed on the MWCNT, interacted with Zn-Fe-DH particles by chemical bonding or electrostatic interactions
Summary
Transition metal-based materials have generated significant interest for applications in energy generation and storage devices (Cheong and Zhitomirsky, 2009; Zhai et al, 2018; Cesano et al, 2019; Chen et al, 2019; Dong et al, 2019). The high power density of 3,700 W kg−1 and energy density of 12 Wh kg−1 were achieved for an asymmetric device, containing FeOOH as a negative and MnO2 as a positive electrode in a voltage window of 1.85 V. The development of new colloidal techniques (Silva et al, 2018) facilitated the fabrication of FeOOH and composite electrodes with active mass of 36–39.6 mg cm−2. Asymmetric devices (Chen et al, 2018) containing α – FeOOH-carbon nanotube negative electrodes and MnO2-carbon nanotube positive electrodes showed good electrochemical performance. Previous investigations showed that the development and testing of double hydroxide materials is a promising avenue for the fabrication of advanced supercapacitor electrodes. An asymmetric device has been fabricated and tested, containing Zn-Fe-DH negative electrodes and polypyrrole-MWCNT positive electrodes
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