Commercial supercapacitors using available carbon products
have
long been criticized for the under-utilization of their prominent
specific surface area (SSA). In terms of carbonaceous electrode optimization,
excessive improvement in SSA observed in the gaseous atmosphere might
have little effect on the final performance because cracked/inaccessible
pore alleys considerably block the direct electrolyte ion transport
in a practical electrochemical environment. Herein, mesopore-adjustable
hierarchically porous carbon nanosheets are fabricated based on a
micelle-size-mediated spatial confinement strategy. In this strategy,
hydrophobic trimethylbenzene in different volumes of the solvent can
mediate the interfacial assembly with a carbon precursor and porogen
segment through π–π bonding and van der Waals interaction
to yield micelles with good dispersity and the diameter varying from
119 to 30 nm. With an increasing solvent volume, the corresponding
diffusion coefficient (3.1–14.3 m2 s–1) of as-obtained smaller micelles increases, which makes adjacent
micelles gather rapidly and then grow along the radial direction of
oligomer aggregates to eventually form mesopores on hierarchically
porous carbon nanosheets (MNC150-4.5). Thanks to the pore-expansion
effect of trimethylbenzene, the mesoporous volume can be adjusted
from 28.8 to 40.0%. Mesopores on hierarchically porous carbon nanosheets
endow MNC150-4.5 with an enhanced electrochemically active surface
area of 819.5 m2 g–1, which gives rise
to quick electrolyte accessibility and a correspondingly immediate
capacitive response of 338 F g–1 at 0.5 A g–1 in a three-electrode system. Electrolyte transport
through pathways within MNC150-4.5 ultimately enables the symmetric
cell to deliver a high energy output of 50.4 Wh kg–1 at 625 W kg–1 in a 14 m LiOTF electrolyte and
95% capacitance retention after 100,000 cycles, which show its superior
electrochemical performance over representative carbon-based supercapacitors
with aqueous electrolytes in recent literature.
Redox active carbonaceous materials have recently absorbed a wide range of interest in energy-related fields owing to their trade-off superiorities between carbon stability and heteroatom activity. Feasible alkali-calcination of heteroatom-rich...
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