Abstract
Porous structure and surface defects are important to improve the performance of supercapacitors. In this study, a facile pathway was developed for high-performance supercapacitors, which can produce transition metal hydroxides (LDHs) with abundant porous structure and surface defects. The NiCo-SDBS-LDH was prepared by one-step hydrothermal reaction using sodium dodecylbenzene sulfonate (SDBS) as anionic surfactant. And then, three dimensional (3D) interconnected porous flower-like 3D-NiCo-SDBS-LDH microspheres were designed and synthesized using the gas-phase hydrazine hydrate reduction method. Results showed that the hydrazine hydrate reduction not only introduces a large number of pores into 3D-NiCo-SDBS-LDH microspheres and causes the formation of oxygen vacancies, but it also roughens the surface of the microspheres. All these changes contribute to the enhancement of electrochemical activity of 3D-NiCo-SDBS-LDH; the NiCo-SDBS-LDH electrode after hydrazine hydrate treatment (3D-NiCo-SDBS-LDH) exhibits a higher specific capacitance of 1148 F·g−1 at 1 A·g−1 (about 1.46 times larger than that of NiCo-SDBS-LDH) and excellent long cycle life with 94% retention after 4000 cycles. Moreover, the assembled 3D-NiCo-SDBS-LDH//AC (active carbon) asymmetric supercapacitor (ASC) achieves remarkable energy density of 73.14 W h·kg−1 at 800 W·kg−1 and long-term cycling stability of 95.5% retention for up to 10,000 cycles. The outstanding electrochemical performance can be attributed to the synergy between the rich porous structure and the roughened surface that has been created by the hydrazine hydrate treatment.
Highlights
Supercapacitors have received a great deal of attention as an energy storage device in the electric vehicle and consumer electronics industries because of their fast charge–discharge features, long cycle stability, and high power densities [1,2,3,4,5]
We present a simple vacuum-assisted hydrazine hydrate reduction strategy for the production of 3D flower-like NiCo-LDH microspheres which are enriched in pores and have surface defects
Hydrazine hydrate was selected as the reducing medium
Summary
Discharge features, long cycle stability, and high power densities [1,2,3,4,5]. due to their low energy density, they are unable to meet the demands of high-performance supercapacitors in the market [6,7]. The improvement in intrinsic conductivity can accelerate the diffusion of ions and promote charge transfer dynamics, resulting in enhancement of electrochemical performance [24,25,26,27] Several modification methods, such as thermal annealing treatment [28,29,30], acid etching [31] or alkali etching [32], NaBH4 reduction treatment [26,33,34], and hydrazine hydrate reduction treatment [24,25,35], have been reported in previous studies to generate the defective structures in electrode materials. Results show that LDH improves electrochemical performance and cycling stability by altering electrode structure of the nanosheets
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