Spatial Confinement Strategy for Micelle-Size-Mediated Modulation of Mesopores in Hierarchical Porous Carbon Nanosheets with an Efficient Capacitive Response

Abstract

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.

Electrochemical Performance of N-Doped Carbon-Based Electrodes for Supercapacitors

“…The variable output of certain types of green alternative energy sources requires an effective method to store electrical energy . Supercapacitors have attracted significant attention as a potential solution because of their ability to be constructed from more environmentally friendly options like carbon-based materials, unlike other electrical storage options. , Additionally, intrinsic properties including fast charge–discharge response time, high power density, and long cycle life make such devices attractive candidates for energy storage solutions. − Such devices combine the high energy density of batteries with the high power density of capacitors. These properties are advantageous because they allow for short-term memory storage in electrical devices, where fast response time is paramount …”

Ni-MOF composite polypyrrole applied to supercapacitor energy storage

“…Hierarchically porous nanomaterials can enhance the electrochemically active surface area, which gives rise to quick electrolyte accessibility and a correspondingly immediate capacitive response in supercapacitor. 38 For example, a unique layered structure of Ni-MOF can store a large number of electrolyte ions, and the huge specific surface area improves the effective utilization rate of the electrode materials. Meanwhile, the introduction of PPy can increase the conductivity, provide conductive channels for electron transmission, and improve the cycle life of energy storage devices with stable structures.…”

Facile design and synthesis of a nickel disulfide/zeolitic imidazolate framework-67 composite material with a robust cladding structure for high-efficiency supercapacitors

“…The CV curves at different scanning rates all have the same shape, and the GCD curves at various current densities are smooth straight lines without potential platforms, which is consistent with the behavior of a typical electric double-layer capacitor. 65,66 Moreover, the specic capacitances of AC is 158.4, 137.6, 118.4, 96.0 and 80.0 F g À1 at 0.5, 1, 2, 5 and 10 A g À1 , respectively.…”