From Water and Ni Foam to a Ni(OH)₂@Ni Foam Binder‐Free Supercapacitor Electrode: A Green Corrosion Route

Abstract

In this work, a Ni(OH)2@Ni foam binder‐free electrode was obtained through the corrosion of Ni foam with ultrapure water under hydrothermal conditions. The structure, morphology, and surface chemical states of the obtained Ni(OH)2@Ni foam were characterized by X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, and X‐ray photoelectron spectroscopy. The chemical formation mechanism is discussed. In addition, it was found that the loading amount and morphology of the deposited Ni(OH)2 depend largely on the corrosion time. Furthermore, electrodes corroded for different times were then directly used as working electrodes to investigate the areal and specific capacitances of the deposited Ni(OH)2 by using cyclic voltammetry, through which a relationship between the corrosion time, loading amount, morphology, and final capacitance is built up. The electrode with the highest areal capacitance was further studied with cyclic voltammetry, galvanostatic charge−discharge processes, as well as electrochemical impedance spectroscopy. The as‐prepared Ni(OH)2@Ni foam is a typical pseudocapacitance electrode. At a high current density of 5 mA cm−2, the electrode exhibits an areal capacitance of 0.863 F cm−2. For the deposited Ni(OH)2, its specific capacitance reaches 693 F g−1 at a current density of 4 A g−1. After 3000 charge−discharge cycles at a current density as high as 10 A g−1 (12.5 mA cm−2), the areal capacitance retains 77.3 % of its initial value. The findings in this work could be meaningful for the corrosion preparation of related electrodes and the design of binder‐free electrodes.

Study on Capacitance of Zn-Based Electrode in Redox Electrolyte System

“…Galvanostatic charge and discharge curves at 1 A•g −1 are shown in Figure 3. In KOH electrolyte, there is a charging/discharging platform, while there are two obvious charging/discharging platforms at about 0.4 and 0.5 V in K 3 [Fe(CN) 6 ] + KOH electrolytes, which further confirms existence of multi-step redox process in K 3 [Fe(CN) 6 ] + KOH system [10].…”

“…In KOH electrolyte, a pair of main redox peaks appeared in CV curve at about 0.34 V and 0.56 V (vs HgO/Hg) at scanning rate of 0.01 V•s −1 , which could be attributed to the transition between Zn(II) and Zn(III) of HZC electrode. The HZC electrode showed typical pseudocapacitance characteristics [10] [11]. In , and the deviation of redox peak may be related to properties of substrate, surface roughness of substrate, or superpotential of electrode [12].…”

Electrochemical studies of Ni(OH) 2 , NiO, and Ni 3 S 2 nanostructures on Ni‐foam toward binder‐free positive electrode for hybrid supercapacitor application

“…24 Liu et al prepared Ni(OH) 2 in Ni-foam by corrosion and showed 863 mF cm À2 , stability up to 77.3% for 3000 cycles. 25 Similar Ni 3 S 2 synthesis studies have been reported using Ni-foam as a conductive matrix 19,[26][27][28][29] or a sacrificial template of Ni(OH) 2 on Nifoam. [30][31][32] These studies included precursor composition and hydrothermal conditions' effect on material growth.…”

“…Using this analogy, Chen et al prepared Ni 3 S 2 nanoparticles on a Ni‐foam electrode delivered 1120 mF cm −2 with no degradation up to 3000 cycles 24 . Liu et al prepared Ni(OH) 2 in Ni‐foam by corrosion and showed 863 mF cm −2 , stability up to 77.3% for 3000 cycles 25 . Similar Ni 3 S 2 synthesis studies have been reported using Ni‐foam as a conductive matrix 19,26‐29 or a sacrificial template of Ni(OH) 2 on Ni‐foam 30‐32 .…”

Construction of NiCo2S4@NiMoO4 Core‐Shell Nanosheet Arrays with Superior Electrochemical Performance for Asymmetric Supercapacitors

“…In order to further improve the rate performance and cycling stability of electrode materials for supercapacitors, one promising strategy is to build three dimensional core‐shell heterostructures combining the advantages of individual materials directly on various substrates, such as cellulose fiber, graphene foam, carbon nanofiber, Ti foil and Ni foam . To date, researchers have successfully constructed a wide variety of well‐defined core‐shell nanostructures with superior supercapacitive performance.…”