Controllable synthesis of 3D binary nickel–cobalt hydroxide/graphene/nickel foam as a binder-free electrode for high-performance supercapacitors

Abstract

10Binder-free electrodes based on 3D porous nickel cobalt binary hydroxides (NCH)/graphene (G) composites on nickel foam (NF) for supercapacitors are fabricated via chemical vapor deposition (CVD) process combined with electrochemical deposition (ED) method. High quality graphene grown on NF makes the surface more suitable for deposition 3D porous NCH and enhances the conductivity of electrode at the same time. The 3D structure can improve the electron transport 15 ability and make more active sites contact with electrolyte sufficiently. The morphology and electrochemical performance of NCH/G/NF electrodes can be readily manipulated by adjusting the deposition current density and the Ni/Co ratio of deposition solution. Attributed to the synergetic effect of the above factors, high capacitance with enhanced stability and rate capability is achieved. Specifically, at the deposition current density of 0.625 mA cm -2 and Ni/Co 20 ratio of 1:1, the NCH11/G/NF electrode exhibits maximum specific capacitance of 1410 F g -1 at 2 A g -1 . When the current density increases to 4 A g -1 , the capacitance is still 1328 F g -1 with high capacitance retention of 94.2 %. After 2500 cycles, the capacitance retention is 92.1 %, which is higher than that of common slurry-coating electrode. To research its practical application, an asymmetric supercapacitor with NCH11/G/NF electrode as positive electrode and activated 25 carbon as negative electrode was fabricated. The asymmetric device exhibits a prominent energy density of 33.75 Wh kg -1 at a power density of 750 W kg -1 . The binder-free electrode with superior performance has been proved to be very promising for energy storage. 65to the nearly identical physical and chemical properties and the miscible ions in aqueous solution of nickel and cobalt. 14 What's more, the binary system not only inherits the merits of their individual components, but also yields much higher electrochemical performance. The atom substitution will 70 increase electrical conductivity and effectively enhance the active-site density and roughness of the final binary product. 15,

Cobalt hydroxide [Co(OH)2] loaded carbon fiber flexible electrode for high performance supercapacitor

“…The present values of energy and power densities are higher than those of recently reported for bare cobalt hydroxide and CF based composite electrodes 32,33 . Fig 4 (c) reflects Ragone plot for CF 40 electrode, the electrode shows high supercapacitive performance with excellent values of energy and power densities, these values in the present case are quite comparable to the recently reported one [34][35][36] . It is seen that at lower current densities, energy densities are high enough, however, decrease with the increase in the discharge current density.…”

Flexible Asymmetric Threadlike Supercapacitors Based on NiCo2Se4 Nanosheet and NiCo2O4/Polypyrrole Electrodes

“…[24,25] In addition, the signal from Se can be definitely observed, as shown in Figure 3d.T he peaks situated at 59.5 and 54.8 eV can be ascribed to Se 3d 3/2 and Se 3d 5/2 ,w hich are typical of metal selenium bonds. The cyclic voltammetry (CV) analysis of the NiCo 2 Se 4 nanosheets is shown in Figure 4a.T he CV curveso fN iCo 2 Se 4 are very similart ot hose of various Ni-Co based electroactive materials, such as Ni-Co oxide, [27][28][29] hydroxides, [30][31][32] and sulfides. The cyclic voltammetry (CV) analysis of the NiCo 2 Se 4 nanosheets is shown in Figure 4a.T he CV curveso fN iCo 2 Se 4 are very similart ot hose of various Ni-Co based electroactive materials, such as Ni-Co oxide, [27][28][29] hydroxides, [30][31][32] and sulfides.…”

Hierarchical ultrathin NiAl layered double hydroxide nanosheet arrays on carbon nanotube paper as advanced hybrid electrode for high performance hybrid capacitors

“…However, LDH suffers from its intrinsic low electrical conductivity and highly packed morphology, resulting in low rate performance and poor cycle life in supercapacitors [14,15]. To overcome this drawback, an effective approach is to design a binder-free electrode incorporating LDH with a conductive substrates such as conductive textile fibers [19], titanium plate [20], stainless steel [21] as well as nickel foam (NF) [22,23]. In such binder-free electrode approach, the traditional manufacture process of the slurry-derived electrode is neglected.…”