Abstract
Electrode material design is the key to the development of asymmetric supercapacitors with high electrochemical performances and stability. In this work, Al-doped NiO nanosheet arrays were synthesized using a facile hydrothermal method followed by a calcination process, and the synthesized arrays exhibited a superior pseudocapacitive performance, including a favourable specific capacitance of 2253 ± 105 F g−1 at a current density of 1 A g−1, larger than that of an undoped NiO electrode (1538 ± 80 F g−1). More importantly, the arrays showed a high-rate capability (75% capacitance retention at 20 A g−1) and a high cycling stability (approx. 99% maintained after 5000 cycles). The above efficient capacitive performance benefits from the large electrochemically active area and enhanced conductivity of the arrays. Furthermore, an assembled asymmetric supercapacitor based on the Al-doped NiO arrays and N-doped multiwalled carbon nanotube ones delivered a high specific capacitance of 192 ± 23 F g−1 at 0.4 A g−1 with a high-energy density of 215 ± 15 Wh kg−1 and power density of 21.6 kW kg−1. Additionally, the asymmetric device exhibited a durable cyclic stability (approx. 100% retention after 5000 cycles). This work with the proposed doping method will be beneficial to the construction of high-performance supercapacitor systems.
Highlights
With the sharply increasing environmental pollution and the energy crisis over the past decades, the development of renewable energy storage systems has been paid increasing attention [1,2], of which supercapacitors have attracted considerable interest due to& 2018 The Authors
A fabricated asymmetric supercapacitor (ASC) based on Al-doped NiO nanosheet arrays and N-doped multiwalled carbon nanotubes (MWCNTs) achieved superior energy density and power density of 215 + 15 Wh kg21 and 21.6 kW kg21, respectively, as well as a robust cycling stability. These findings demonstrate that the nanosheets can function as binder-free supercapacitor electrodes with improved capacitive performances, which can address the challenge for the application of NiO in electrochemical energy storage devices and beyond
The ASC was assembled based on an Al-doped NiO array directly as an electrode, the N-doped MWCNT electrode and 1 M KOH, which were used as the positive electrode, the negative electrode and the electrolyte, respectively
Summary
With the sharply increasing environmental pollution and the energy crisis over the past decades, the development of renewable energy storage systems has been paid increasing attention [1,2], of which supercapacitors have attracted considerable interest due to. Their quick charge/discharge rate, long lifespan, ultrahigh power density and reliability [3,4,5,6]. Compared with undoped NiO nanoarrays, the as-prepared Al-doped NiO nanosheets exhibited a higher capacitance (1679 + 46 F g21 at 20 A g21), namely approximately 50–168% improvement in the specific capacitance It showed a good cycling behaviour (1% capacitance loss after 5000 cycles) and a wonderful rate capability These findings demonstrate that the nanosheets can function as binder-free supercapacitor electrodes with improved capacitive performances, which can address the challenge for the application of NiO in electrochemical energy storage devices and beyond
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