An Amorphous–Crystalline Nanosheet Arrays Structure for Ultrahigh Electrochemical Performance Supercapattery

Abstract

SCs suitable for many different occasions. [1][2][3][4][5][6][7] However, the low energy density limits their extensive commercial applications. Based on the above, hybrid supercapacitors (HSCs) also called supercapattery with battery-type positive electrode as the energy source and electric double-layer capacitor negative electrode as the power source have been designed, it combines the dual advantages of high power density of traditional SCs and high energy density of batteries. [7][8][9][10] Further, the electrochemical properties of the HSCs are mainly determined by the battery-type electrode, so selecting suitable electrode materials or optimizing the electrode structure is essential for obtaining high-performance hybrid devices.Transition metal oxides and sulfides have become the most widely studied battery-type electrodes due to their remarkable electrochemical activity and high specific capacity. [11][12][13] For example, Chen et al. reported the self-supported Ni 3 S 2 nanosheet arrays by a two-step method. Benefiting from its unique 3D sheet structure, the electrode shows superb rate capability and energy density. [14] Kim et al. designed the independent electrode of NiMo 2 S 4 using the successive ionic layer adsorption and reaction (SILAR) method, which also showed high reversible specific capacity. [15] Although some progress has been made in the research of battery-type electrodes, the inherent physical and chemical properties of the single electrode materials may limit the further development. In order to achieve higher electrochemical performance, complex and stable electrode structures are required to be constructed.In the previous work, the first-principles calculations show that amorphous oxides (such as MnO 2 , [16] ) can produce lots of unsaturated suspension bonds, which makes them have a broad application prospect in the field of energy storage. [18][19][20] Liu et al. proposed amorphous manganese oxide as the pseudocapacitive electrode, which proved to possess excellent rate capability and high cycle stability. [21] This may be due to the fact that the loose arrangement of atoms and ions is more conducive to rapid ion transport of the active materials in the bulk of oxides. Sun et al. successfully synthesized MoO 3 by electrochemical deposition technique and pointed out that the disordered structure is likely to release the structural stress caused by the repeated ion deintercalation/intercalation behavior, thus Hybrid supercapacitors (HSCs), also called supercapattery, which can substitute for low power density batteries have attracted extensive interest. However, when HSCs comes to commercial applications, there is still space for improvement in energy density. It seems that designing of electrode with high capacity is an effective measure. Herein, amorphous-crystalline MoO 3 -Ni 3 S 2 /NF-0.5 nanosheet arrays are developed as battery-type electrodes. Specifically, the sheet-like structure of crystalline Ni 3 S 2 can achieve rich structural nanocrystallization, improving the redox reacti...

In‐situ nano‐engineering of amorphous MoS 2 nanosheets with carbon dots for enhanced supercapacitor performances

“…A CV curve at 1 mV s −1 and capacitive contribution curve is presented in Figure 4B, showing overflow of the capacitive contribution curve. We think that this overflow of the capacitive contribution curve from original CV curve is due to the relationship of polarization, the potential will move at different sweep rates 44 . In the near peak current, the value of i will be different at same potential.…”

“…Figure S8 shows the CV curves from 1 to 4 mV s −1 showing pair of redox peaks indicating battery‐like behavior of the electrode material. The peak currents (i) are plotted as a function of square root of sweep rate (v b ) plotted based on the following equation 44 : …”

“…In the near peak current, the value of i will be different at same potential. This could be the reason of capacitive contribution curve is overflowing from original CV curve 44 . The diffusion contribution for a‐MoS 2 /C‐dots composites at 1 mV s −1 was calculated to be 60%, and contribution at 2, 3, and 4 mV s −1 scan rates were obtained to be 56%, 52%, and 49%, respectively, showing a typical battery‐type faradic behavior 46 of a‐MoS 2 /C‐dots composites as shown in Figure 4C.…”

“…We think that this overflow of the capacitive contribution curve from original CV curve is due to the relationship of polarization, the potential will move at different sweep rates. 44 In the near peak current, the value of i will be different at same potential. This could be the reason of capacitive contribution curve is overflowing from original CV curve.…”

“…This could be the reason of capacitive contribution curve is overflowing from original CV curve. 44 The diffusion contribution for a-MoS 2 /C-dots composites at 1 mV s À1 was calculated to be 60%, and contribution at 2, 3, and 4 mV s À1 scan rates were obtained to be 56%, 52%, and 49%, respectively, showing a typical battery-type faradic behavior 46 of a-MoS 2 /C-dots composites as shown in Figure 4C. Electrochemical impedance spectroscopy (EIS) was performed to demonstrate the ion transport and conductivity for the as-synthesized composites in 2 M KOH electrolyte at a frequency range of 100 kHz to 0.1 Hz under OCP (open circuit potential).…”