A hierarchical
structure, defined as structural features occurring
on different levels of scale, is widely used in the rational design
of composite electrodes for its superiorities in abundant electrochemical
active sites and functional differentiation for various components.
Herein, we in situ prepare a nickel–cobalt
layered double hydroxide (NiCo-LDH) nanosheet network on ultrathin
nickel–cobalt–zinc–sulfide (NiCoZnS
x
) microplate arrays to construct a special, coral-inspired
hierarchical structure. In this structure, NiCoZnS
x
microplate arrays not only provide plenty of rooms for
nanosheet growth but also improve the ion diffusion, charge transfer,
and structural stability of the composite electrode. The NiCo-LDH
nanosheet network paved through the microplate surface offers a high
specific surface area and capacitance. The composite electrode delivers
a high specific capacitance of 8.1 F cm–2 (1928
F g–1) at a loading mass of 4.2 mg cm–2, outstanding rate capability (63% capacitance retention, 50 mA cm–2), and cycling stability (80% capacitance retention,
10 000 cycles). Furthermore, the hybrid asymmetric supercapacitor
assembled by the composite electrode and active carbon exhibits a
maximal power density of 80.3 mW cm–2 at an energy
density of 270 μWh cm–2 with good rate capability
and cycling stability. This work reveals the significance and practical
potential of rational design in the electrode’s hierarchical
structure for a high-performance supercapacitor.
NiCo-based layered double hydroxides (NiCo-LDHs) have superior properties as electrode materials for supercapacitors, but poor cycle performance significantly limits their application. An effective strategy to tackle this issue is to dope inactive Al that could stabilize the metallic layers to form ternary hydroxides. However, the desired ternary electrodes with appropriate content of Al3+ are difficult to prepare by conventional electrodeposition due to the great difference in solubility product constants (Ksp) of corresponding hydroxides, where the non-electroactive Al(OH)3 (Ksp=1.3×10‒33) are preferentially deposited rathjer than the hydroxides of nickel and cobalt (Ksp=2.0×10‒15, 1.6×10‒15). Here, we propose a novel electrodeposition method assisted by F‒ to control Al3+ content in NiCoAl-LDHs. By adjusting the concentration of F‒ in the electrolyte, Al3+ content, as well as the morphology and electrochemical performance of the electrodes, could be manipulated. With the optimum ratio of F‒ to Al3+, the as-obtained electrode shows high specific capacitance along with a long lifespan (54.1%, 10000 cycles). An asymmetric supercapacitor is assembled using active carbon as the negative electrodes, which displays the maximal energy density of 35.5 Wh kg−1 at the power density of 477.3 W kg−1, with a long lifespan (75%, 10000 cycles).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.