Abstract
Zinc–ion hybrid supercapacitors are a promising energy storage device as they simultaneously combine the high capacity of batteries and the high power of supercapacitors. However, the practical application of Zinc–ion hybrid supercapacitors is hindered by insufficient energy density and poor rate performance. In this study, a symmetrical zinc–ion hybrid supercapacitor device was constructed with hollow mesoporous-carbon nanospheres as electrode materials, and aqueous ZnSO4 adopted as an electrolyte. Benefiting from the mesoporous structure and high specific area (800 m2/g) of the hollow carbon nanospheres, fast capacitor-type ion adsorption/de-adsorption on both the cathode and the anode can be achieved, as well as additional battery-type Zn/Zn2+ electroplating/stripping on the anode. This device thus demonstrates outstanding electrochemical performance, with high capacity (212.1 F/g at 0.2 A/g), a high energy density (75.4 Wh/kg at 0.16 kW/kg), a good rate performance (34.2 Wh/kg energy density maintained at a high power density of 16.0 kW/kg) and excellent cycling stability with 99.4% capacitance retention after 2,500 cycles at 2 A/g. The engineering of this new configuration provides an extremely safe, high-rate, and durable energy-storage device.
Highlights
With the continuous development of electric vehicles, smart electric grids, and miniaturized electronics, it is important to develop high–performance electrochemical energy storage systems (Sun et al, 2018; Zhang et al, 2019)
The construction of better energy storage devices relies on the structure design of electrode materials, and more crucially, it depends on the engineering of the device configuration (Zhang et al, 2014; Zuo et al, 2017; Chen et al, 2019b)
A symmetrical zinc–ion hybrid supercapacitor system was constructed using mesoporous-carbon nanospheres with a hollow structure as both anode and cathode materials, as well as aqueous ZnSO4, which was adopted as an electrolyte
Summary
With the continuous development of electric vehicles, smart electric grids, and miniaturized electronics, it is important to develop high–performance electrochemical energy storage systems (Sun et al, 2018; Zhang et al, 2019). Aqueous zinc–ion hybrid supercapacitors (ZHSs) have recently emerged as promising energy storage devices, due to the intrinsic advantages of the zinc element, such as a high capacity of 820 mAh/g in theory, low redox potential of −0.76 V vs a standard hydrogen electrode (Ma et al, 2018; Chen et al, 2019a; Yu et al, 2019). Dong et al have constructed a novel ZHS device using Zn metal and activated carbon as an anode and a cathode, respectively This device revealed a high capacity of 121 mAh/g (84 Wh/kg) at 0.1 A/g current density, a high cycling stability of 91% capacity retention after 10 k charge/discharge cycles at 1 A/g (Dong et al, 2018). A symmetrical zinc–ion hybrid supercapacitor system was constructed using mesoporous-carbon nanospheres with a hollow structure as both anode and cathode materials, as well as aqueous ZnSO4, which was adopted as an electrolyte. Cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) measurements were applied to characterize the electrochemical performance of the constructed devices
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