Rational Design of Sandwiched Ni–Co Layered Double Hydroxides Hollow Nanocages/Graphene Derived from Metal–Organic Framework for Sustainable Energy Storage

Abstract

In situ growth of Ni–Co layered double hydroxides on graphene nanosheets by virtue of metal–organic framework as a sacrifice template is reported, which yields hollow nanocages uniformly deposited on graphene nanosheets. The strong impact of graphene amount on the electrochemical performance of Ni–Co layered double hydroxides is illustrated. Controlling the mass of graphene (15 mg) leads to a maximum specific capacitance of 1265 F g–1, high rate capability (50% capacitance retention after increasing current density ten times), and good cycling life (92.9% capacitance retention after 2000 circles). The combination of battery-type Ni–Co LDH hollow nanocages/graphene composite and active carbon allows for the excellent electrochemical performance measured in an asymmetric device. In detail, the assembled asymmetric supercapacitor is able to deliver maximum specific capacitance 170.9 F g–1 in a potential window of 0–1.7 V, high energy density (68.0 Wh kg–1), as well as excellent power output (4759 W kg–1). These electrochemical performances, in combination with its facile fabrication, render hollow Ni–Co LDH/graphene composite as a promising electrode material in a sustainable energy storage device.

Hierarchical PANI/NiCo-LDH Core-Shell Composite Networks on Carbon Cloth for High Performance Asymmetric Supercapacitor

“…Meanwhile, all the nearly symmetric GCD curves reveal that the redox reactions between the PANI/LDH-200 electrode and KOH eletrolyte are highly reversible. Impressively, the PANI/LDH-200 delivers the largest capacitances of 1845 F g −1 at a current density of 0.5 A g −1 , which is superior to those of other reported LDH-based composite electrodes [17,39,40,41,42,43] as shown in Table S2.…”

Anion Exchange of Ni–Co Layered Double Hydroxide (LDH) Nanoarrays for a High‐Capacitance Supercapacitor Electrode: A Comparison of Alkali Anion Exchange and Sulfuration

“…The binding energy shows a decrease of around 0.5 eV after anion exchange or the sulfidation process, owing to the different chemical environment . For all samples, the fitting of Co 2p 3/2 peaks clearly highlights the coexistence of two oxidation states, with the Co 3+ component at 780.4 eV and the Co 2+ component at 781.2 eV . The presence of the Co 3+ component, originated from the hydrothermal oxidation of Co 2+ in alkaline media by solved oxygen, is important for the formation of NiCo LDH.…”

Heterogeneous assembly of Ni–Co layered double hydroxide/sulfonated graphene nanosheet composites as battery-type materials for hybrid supercapacitors

“…Even at a power density of 8000 W g -1 , the hybrid supercapacitor still retains an energy density of 28 Wh kg -1 , superior to most recently reported devices based on Ni, Co, and other transition metal compounds. 21,22,[59][60][61][62] As can be seen in Fig. 7f, the hybrid supercapacitor exhibits excellence cycling performance with the capacitance retention of 94% in continuous operation of 10 000 cycles.…”