Exfoliated Mesoporous 2D Covalent Organic Frameworks for High‐Rate Electrochemical Double‐Layer Capacitors

Abstract

The electrochemical double‐layer capacitors (EDLCs) are highly demanded electrical energy storage devices due to their high power density with thousands of cycle life compared with pseudocapacitors and batteries. Herein, a series of capacitor cells composed of exfoliated mesoporous 2D covalent organic frameworks (e‐COFs) that are able to perform excellent double‐layer charge storage is reported. The selected mesoporous 2D COFs possess eclipsed AA layer‐stacking mode with 3.4 nm square‐like open channels, favorable BET surface areas (up to 1170 m2 g−1), and high thermal and chemical stabilities. The COFs via the facile, scalable, and mild chemical exfoliation method are further exfoliated to produce thin‐layer structure with average thickness of about 22 nm. The e‐COF‐based capacitor cells achieve high areal capacitance (5.46 mF cm−2 at 1,000 mV s−1), high gravimetric power (55 kW kg−1), and relatively low τ0 value (121 ms). More importantly, they perform nearly an ideal DL charge storage at high charge–discharge rate (up to 30 000 mV s−1) and maintain almost 100% capacitance stability even after 10 000 cycles. This study thus provides insights into the potential utilization of COF materials for EDLCs.

Ultralight Covalent Organic Framework/graphene Aerogels with Hierarchical Porosity

“…4f). In the Nyquist plots, the straight line at the low-frequencies reveals convenient ion transport path, while the small semicircle at the high-frequencies indicates very low internal electrode-electrolyte resistance and efficient charge mobility in the capacitor device 9 . Therefore, it can be concluded that the 3D structure of COF/rGO material is beneficial for the rapid charge transfer and ion diffusion to redox-active sites, providing guarantee for the outstanding electrochemical performance of the supercapacitor.…”

Nickel Alloying Significantly Enhances the Power Density of Ruthenium‐Based Supercapacitors

“…C) Ragone plot, presenting a comparison between current work (black circles) and devices comprising vertically aligned CNTs (blue circles), [10] MoSe 2 (red triangulars), [46] MXene/polymer (green diamonds), [27] and covalent organic framework (brown squares). [15] excellent capacitor behavior, accounting for the linear respond of the voltage and the low IR-drop (0.06 V at 200 mA cm À 2 ), even in current densities up to 2000 mA cm À 2 , which is among the highest areal current densities reported for such thin layers. [10,15,27,46] This areal current density also corresponds to a high volumetric current density of more than 300 A cm À 3 for the entire device, including the current collector and spacer, which is significantly higher than commercial capacitors.…”

“…[15] excellent capacitor behavior, accounting for the linear respond of the voltage and the low IR-drop (0.06 V at 200 mA cm À 2 ), even in current densities up to 2000 mA cm À 2 , which is among the highest areal current densities reported for such thin layers. [10,15,27,46] This areal current density also corresponds to a high volumetric current density of more than 300 A cm À 3 for the entire device, including the current collector and spacer, which is significantly higher than commercial capacitors. Indeed, considering that the thickness of the active layer is less than 2 % of the overall volume of the device, the volumetric current density may be easily further increased upon reducing the thickness of the Ni current collector (currently 20 μm).…”

“…[10] Motivated by these studies, research on SCs which can operate at high frequency/scan rates have mostly focused on devices based upon electric double-layer capacitor (EDLC) mechanisms. Materials such as onion-like carbon, [11] mesoporous carbon, [12][13][14] covalent organic frameworks, [15] and exfoliated graphene, [16] have been promoted as candidates for highfrequency EDLC-based supercapacitors. Yet, low material densities and reduced specific capacitance generally require high mass loading in such devices in order to achieve high capacitance.…”

Nanoscale covalent organic frameworks as theranostic platforms for oncotherapy: synthesis, functionalization, and applications

“…151 Some examples for the preparation of NCOFs by ultrasonic exfoliation are shown in Table 2. [150][151][152][153][154][155][156][157][158][159][160][161][162][163][164][165] Evidently, the weaker the interactions between the COF layers, the easier it becomes to perform ultrasonic exfoliation. TPA-COF constructed with tris(4-aminophenyl)amine and tris(4-formylphenyl)amine exible monomers with the C 3v symmetry conrmed this prediction.…”