Conductive MOF electrodes for stable supercapacitors with high areal capacitance

Abstract

Owing to their high power density and superior cyclability relative to batteries, electrochemical double layer capacitors (EDLCs) have emerged as an important electrical energy storage technology that will play a critical role in the large-scale deployment of intermittent renewable energy sources, smart power grids, and electrical vehicles. Because the capacitance and charge-discharge rates of EDLCs scale with surface area and electrical conductivity, respectively, porous carbons such as activated carbon, carbon nanotubes and crosslinked or holey graphenes are used exclusively as the active electrode materials in EDLCs. One class of materials whose surface area far exceeds that of activated carbons, potentially allowing them to challenge the dominance of carbon electrodes in EDLCs, is metal-organic frameworks (MOFs). The high porosity of MOFs, however, is conventionally coupled to very poor electrical conductivity, which has thus far prevented the use of these materials as active electrodes in EDLCs. Here, we show that Ni(2,3,6,7,10,11-hexaiminotriphenylene) (Ni(HITP)), a MOF with high electrical conductivity, can serve as the sole electrode material in an EDLC. This is the first example of a supercapacitor made entirely from neat MOFs as active materials, without conductive additives or other binders. The MOF-based device shows an areal capacitance that exceeds those of most carbon-based materials and capacity retention greater than 90% over 10,000 cycles, in line with commercial devices. Given the established structural and compositional tunability of MOFs, these results herald the advent of a new generation of supercapacitors whose active electrode materials can be tuned rationally, at the molecular level.

The way to improve the energy density of supercapacitors: Progress and perspective

“…The surface area and porosity of MOFs far exceed those of activated carbon (AC), potentially challenging the leading role of carbon electrodes in EDLCs [36], whereas MOFs conventionally coupled with exhibiting an extremely low electrical conductivity, which has thus far prevented the use of MOFs as electrode materials in EDLCs. Very recently, Dincǎ et al [37] showed that porous MOF Ni 3 (HITP) 2 has a high electrical conductivity and is a promising electrode material for use in EDLCs; a large capacitance of~18 μF cm −2 was achieved without the use of any conductive additives or other binders, which is greater than the capacitance achieved using most carbon-based electrodes. Based on SCIENCE CHINA Materials.…”

Our Contributions in Nanochemistry for Antibiosis, Electrocatalyst and Energy Storage Materials

“…At the end of this portion, what we want to introduce is the application of metal oxide frameworks (MOFs). [38] As known, MOFs, a class of highly porous materials, have attracted researchers' attention a lot since 1990s. [39] Facing two intrinsic problems of MOFs (insufficient mechanical/ chemical stability and low electrochemical conductivity), we took measures to enhance the pseudocapacitiance of MOFs by doping metal oxides into the system with one-step precipitation.…”

Recent progress in carbon-based nanoarchitectures for advanced supercapacitors

“…Hence, the exploitation of energy storage devices to efficiently store renewable energy is critical [4]. Among the various energy storage systems (EESs), supercapacitors (SCs) have been regarded as one of the most promising emerging energy storage device because of their significantly long cycling life and high power density [5][6][7]. However, their practical applications have been seriously restricted by the relatively low energy density of SCs, which is mainly related to the structures and properties of active materials.…”

“…In general, carbon materials are commonly used in EDLCs as electrode materials. Conventional EDLCs store the charge by ion adsorption at high-surface-area porous carbon electrodes [7,8]. But the amorphous structure and rich microporous structure of carbon electrodes can lead to low electrical conductivity and high charge transfer resistance, resulting in significantly capacitive performance decay at high current density [9].…”