Sandwich‐Type Microporous Carbon Nanosheets for Enhanced Supercapacitor Performance

Abstract

Sandwich‐type microporous hybrid carbon nanosheets (MHCN) consisting of graphene and microporous carbon layers are fabricated using graphene oxides as shape‐directing agent and the in‐situ formed poly(benzoxazine‐co‐resol) as carbon precursor. The reaction and condensation can be readily completed within 45 min. The obtained MHCN has a high density of accessible micropores that reside in the porous carbon with controlled thickness (e.g., 17 nm), a high surface area of 1293 m2 g−1 and a narrow pore size distribution of ca. 0.8 nm. These features allow an easy access, a rapid diffusion and a high loading of charged ions, which outperform the diffusion rate in bulk carbon and are highly efficient for an increased double‐layer capacitance. Meanwhile, the uniform graphene percolating in the interconnected MHCN forms the bulk conductive networks and their electrical conductivity can be up to 120 S m−1 at the graphene percolation threshold of 2.0 wt.%. The best‐practice two‐electrode test demonstrates that the MHCN show a gravimetric capacitance of high up to 103 F g−1 and a good energy density of ca. 22.4 Wh kg−1 at a high current density of 5 A g−1. These advanced properties ensure the MHCN a great promise as an electrode material for supercapacitors.

Carbon Nanosheets: Synthesis and Application

“…The thickness of the CNSs can be tuned to 17 and 36 nm. [19] By utilizing the bridging effect of asparagine between GO and the polymer,t he thickness of hierarchical porous CNSs can be precisely controlled over the nanometer length scale by wet-chemistry synthesis. The average thicknesses of the carbon coatings are measured to be (9.9 AE 1), (17 AE 2), (71 AE 3), and (82 AE 3) nm with carbon precursor/GO ratios of 15.1:1, 25.3:1, 86.5:1,a nd 100:1,r espectively.…”

“…CNSs have been prepared through many routes, such as chemicalv apor deposition (CVD), [16] solvothermal synthesis, [17] chemicalo rp hysical exfoliation, [18] templating, [19] and self-assembly. [20] There are some unique demands for each method: hydrocarbon gasesa re neededa sp recursors in the CVD process, al ayered structure and weak interactions between layers in the precursors are desired for expansion and exfoliation in chemicalo rp hysicale xfoliation, whereas monomers and small molecules are suitable for templating and self-assembly to synthesize CNSs.C arbon precursors are easily decomposed and the intermediates are prone to polymerization during solvothermalprocessing.…”

Synthesis of activated carbon nanospheres with hierarchical porous structure for high volumetric performance supercapacitors

“…Unfortunately, the surface utilization rates of those activated porous carbons are still very low, which is demonstrated by their small areal specific capacitances of 8-12 μF cm -2 in comparison with the theoretical values of 25-40 μF cm -2 for porous carbon electrodes [17]. Moreover, the developed porosity simultaneously resulted in a low mass density and therefore enormously reduced volumetric performance, which is a crucial parameter in practical applications [18][19][20][21][22]. Gogotsi et al even suggested that the volumetric performance should be more reliable than the gravimetric one when estimating the capacitive performance of supercapacitor electrodes, especially for portable and compact energy storage systems [23].…”

N,O-codoped porous carbon nanosheets for capacitors with ultra-high capacitance

“…doping, could further benefit the specific capacity by improving the electrolyte permeability, ion adsorbing, and so on [33][34][35]. Therefore, engineering the morphology and surface chemistry of carbon materials for EDLCs based on redox-active electrolyte is thus highly desirable while still very challenging [36][37][38].…”