Hybrid aqueous supercapacitors based on mesoporous spinel-analogous Zn-Ni-Co-O nanorods: Effect of Ni content on the structure and energy storage

The structure and the electrochemical performance of mesoporous spinel-analogous Zn-Ni-Co-O (Zn1-xNixCo2O4; 0.2 <= x <= 0.8) nanorods are investigated. Cyclic voltammetry gives strong indication that the charge storage mechanism is governed by pore surface redox processes without significant contribution from the sub-surface charge storage. Since the size of the Zn1-xNixCo2O4 rods decreases with increasing Ni content x, the BET surface and thus the charge storage capacity increases with increasing x, namely from 266 C g(-1) to 463 C g(-1) at 3.12 A g(-1) when increasing x from 0.2 to 0.8. Hybrid aqueous supercapacitors (HSC) are fabricated with Zn1-xNixCo2O4, activated carbon (AC) and 6 M KOH as positive electrode, negative electrode and electrolyte, respectively. The specific energy densities of HSC are in the range of 27-2 Wh kg(-1) at the specific power densities range of 780-2240 W kg(-1). Real-world usage of the aqueous HSC device is demonstrated by enlightening a red light-emitting diode. These outcomes show that the mesoporous spinel-analogous Zn-Ni-Co-O materials are potential candidates for next-generation electrochemical energy storage applications. (C) 2021 Elsevier B.V. All rights reserved.