A high energy density asymmetric all-solid-state supercapacitor based on cobalt carbonate hydroxide nanowire covered N-doped graphene and porous graphene electrodes

Abstract

In order to achieve high energy densities, an asymmetric all-solid-state supercapacitor is developed by synthesizing a novel composite of cobalt carbonate hydroxide (CCH) nanowire covered N-doped graphene (NG) as positive and porous NG as negative electrodes. The CCH-NG composite is obtained from a one-step hydrothermal method, where optimization of the CCH content triples the specific capacitance of porous NG, reaching 1690 F g -1 at 1.0 A g -1 . The optimal composite exhibits a remarkable cycling stability retaining 94.2% of the initial capacitance after 10,000 cycles, and good rate capability (still 1358 F g -1 at 10 A g -1 ). The assembled asymmetric supercapacitor based on the optimal composite has a high discharge areal capacitance of 153.5 mF cm -2 (at 1.0 mA cm -2 ), can cycle reversibly in the high-voltage region of 0~1.9 V, and thus provide superior energy and power densities (0.77 Wh m -2 , 25.3 W m -2 ). 6 dryer for one day. Pure CCH was also prepared hydrothermally under the same conditions but without GO. Porous NG was synthesized by nearly the same procedure but using a high concentration GO aqueous suspension of 4 mg mL -1 . The as-prepared NG hydrogel was taken out of the autoclave with a tweezer and immersed in 1 M KOH aqueous solution overnight. CharacterizationsThe products were characterized by X-ray diffraction (XRD) with a D/Max-RA X-ray diffractometer (Cu Kα =1.5418 Å radiation) at 2 o /min. The elements' valence states were examined by X-ray photoelectron spectroscopy (XPS) in a Thermo VG Scientific MultiLab ESCA2000 system with a CLAM4 hemispherical analyzer at a base pressure below 3×10 -10 mbar. Morphology and sizes the products were analyzed by field-emission scanning electron microscopy (FE-SEM) on S-4800 (Hitachi) at 10 kV. Energy dispersed X-ray spectroscopy (EDS) was performed on the same FE-SEM microscope. Transmission electron microscopy (TEM), high resolution TEM, and selected area electron diffraction (SAED) were carried out on a JEM-2100 (JEOL) at an acceleration voltage of 200 kV. Fourier transform infrared (FT-IR) spectra were recorded with a Varian 3100 FTIR spectrometer. Thermogravimetric analysis (TGA) was performed on a TGA/SDTA thermogravimetric analyzer from room temperature (r.t.) to 800°C in air at a heating rate of 20 o C min -1 . Electrochemical measurements of electrode materialsNickel foams were ultrasonicated in 1 M NaOH for 10 min, and then washed with 1 M HCl, ethanol, and deionized water successively. The CCH-NG electrode was

Boosting the cycling stability of transition metal compounds-based supercapacitors

“…2) the good electrical conductivity of graphene reduces the impact of poor conductivity of transition metal compounds on their electrochemical performance. A variety of transition metal oxide/hydroxide and sulfide materials with different morphologies including nanodots, [54] nanocrystals, [211,212] nanowires, [213] nanosheets, [214,215] and flower-like structure [216] have been used to combine with graphene to form high performance composite materials. We take A g -1 (Figure 11b).…”

Flexible Asymmetric Supercapacitors Based on Nitrogen‐Doped Graphene Hydrogels with Embedded Nickel Hydroxide Nanoplates

“…[28] Dry GO (600 mg) was dispersed ultrasonically in deionized water (150 mL) by using a high-power horntype ultrasound sonicator ( Figure S1) for 1 h, which resulted in a homogeneous dispersion with a GO concentration of 4 mg mL À1 ; the ultrasound power was typically 540 W. Subsequently, NiCl 2 ·4 H 2 O (83 mg) was added to the GO dispersion (34 mL), which led to a Ni 2+ concentration of 0.35 mm. The pH was adjusted to 14 with NaOH with stirring for 1 h. Ethylenediamine (1 mL) was added over 15 min with stirring.…”

“…The use of high-power ultrasound leads to hierarchically porous micron-scale sheets that consist of a highly interconnected 3 D NG network in which Ni(OH) 2 nanoplates are well dispersed, which avoids the stacking of NG, Ni(OH) 2 docapacitance, low cost, and environmental compatibility. [26][27][28] Ni(OH) 2 nanocrystals with well-defined morphologies are desired, as demonstrated by some metal oxides and hydroxides. [29,30] For example, Ni(OH) 2 particles/G composite hydrogels exhibited a specific gravimetric capacitance of 1250 F g À1 at 10 mV s…”

Unifying miscellaneous performance criteria for a prototype supercapacitor via Co(OH)2 active material and current collector interactions

“…Given the influence the choice of current collector can have on morphological and structural properties of the active material, ranging from specific surface and porosity to particle size and size distribution (Cao et al, 2004;Simon & Gogotsi, 2008;Bae et al, 2011;Wang et al, 2012;Zhang & Lou, 2013;Bai et al, 2015), it is perhaps unsurprising that there has been considerable interest in this area. Although has been considerable interest in forming nanostructures of the active material in order to obtain a high specific surface area, which has been found to affect the density of electrochemically active sites (Simon & Gogotsi, 2008;Lu et al, 2013), one other approach to improving performance is to use porous substrates, which, by providing electrolyte channels through the electrode that maximize contract with the active material, can enhance the charge transfer process (Cao et al, 2004;Kong et al, 2010;Zhang & Lou, 2013;Bai et al, 2015;Xie et al, 2015).…”

“…Moreover, by using a substrate with high conductivity, it may be possible to utilize fast electron transport channels, which facilitate the collection of the electrons (Choi et al, 2013;Zhang & Lou, 2013;Xie et al, 2015;Gu et al, 2016;Hu et al, 2016). From this it can be seen that the effect of the substrate on electrode performance may be considerable, though to date there has been little research into the effect of substrates on modifying the charge transfer and electron transport processes between the electrode and electrolyte.…”