Rational Assembly of CoAl‐Layered Double Hydroxide on Reduced Graphene Oxide with Enhanced Electrochemical Performance for Energy Storage

Abstract

In this paper, we designed and synthesized composites of CoAl‐layered double hydroxide on reduced graphene oxide (CoAl‐LDH@rGO/NF) via a facile approach. The Co‐Al layered double hydroxide (CoAl‐LDH) nanosheets were grown onto the skeleton of reduced graphene oxide on Ni foam (rGO/NF). The as‐synthesized CoAl‐LDH@rGO/NF composites exhibited a superior electrochemical behavior, attributed to the coupling effect of homogeneous CoAl‐LDH nanosheets and high conductivity of rGO. In addition, the different morphologies of the CoAl‐LDH@rGO/NF composites can be controlled by adjusting the amount of NH4F. The optimum electrochemical performance of the CoAl‐LDH@rGO/NF hybrid electrode was obtained when the amount of NH4F was 6 mmol. The largest specific capacitance of 1671.4 F g−1 (1 A g−1) and the ultra‐high cycling performance with 97 % retention of the original value were achieved even after 5000 charge‐discharge cycles. A remarkable energy density value of 41.3 Wh kg−1 at a power density of 408.9 W kg−1 was achieved in the asymmetric supercapacitor (ASC) using CoAl‐LDH@rGO‐6/NF and activated carbon (AC) for positive and negative materials. Furthermore, the ASC retained 100 % of its original energy density value even after 5000 cycles. In addition, a design method for preparing high performance electrode materials with ideal morphology is proposed in this paper, which might be helpful to the future study of morphology and electrochemical properties.

Surface Engineering of Graphene Oxide Shells Using Lamellar LDH Nanostructures

“…These results prove good mechanical stability in real-time application. NiAl LDH/graphene 43 hydrothermal corrugated and scrolled sheets 781 F g −1 at 5 mV s −1 graphene/NiAl LDH 44 hydrothermal followed by chemical reduction nanosheets 915 F g −1 at 2 A g −1 CoAl LDH/rGO 45 layer-by-layer assembly nanosheets 1204 F g −1 at 5 mV s −1 CoAl LDH/rGO 46 electrostatic heteroassembly heterostacked LDH and rGO nanosheets 450 F g −1 at 5 A g −1 GNS/CoAl LDH 47 reflux method laminated structure 711 F g −1 at 1 A g −1 rGO/CoAl LDH 48 electrostatic self-assembly hexagonal morphology 825 F g −1 at 1 A g −1 CoAl LDH/rGO/nickel foam 49 hydrothermal method 3D nanosheets 1671 F g −1 at 1 A g −1 CoNi LDH/rGO 46 electrostatic heteroassembly heterostacked LDH and rGO nanosheets 650 F g −1 at 5 A g −1…”

α- and β-Phase Ni-Mg Hydroxide for High Performance Hybrid Supercapacitors

“…Doping or partially substituting with other metal ions, such as Mg [21,22], Al [23][24][25][26], Mn [27], Fe [4], Co [28][29][30][31][32] or Zn [33] in α-Ni(OH) 2 has found to be an effective way to stabilize the crystal structure; the resulting complex nickel hydroxides have demonstrated much improved electrochemical properties and performance when used as electrodes in supercapacitors. For example, α-phase NiCoMn hydroxide demonstrated high power densities and high energy [34], CoAl hydroxide possessed enhanced electrochemical performance [35,36]. Among these metal ions, Mg is an alkaline-earth metals with smaller atomic weight.…”

Rationally engineered 3D-dendritic cell-like morphologies of LDH nanostructures using graphene-based core–shell structures

“…These 3D nanostructure offers a large surface area, short ion diffusion path and more efficient contact between the ions of the active material and the electrolyte thereby enhancing the specific capacitance. A comparative of the material performance with that of similar materials systems reported in literature [42][43][44][45][46][47][48][49][50][51] is shown in Fig. 6d.…”