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Nano Research

Article Title

Hierarchically porous carbon foams for electric double layer capacitors

Keywords

hierarchically porousstructure, glutaraldehyde-crosslinkedchitosan, light weight, carbon foam, electrical double layercapacitors

Abstract

The growing demand for portable electronic devices means that lightweightpower sources are increasingly sought after. Electric double layer capacitors(EDLCs) are promising candidates for use in lightweight power sources due totheir high power densities and outstanding charge/discharge cycling stabilities.Three-dimensional (3D) self-supporting carbon-based materials have beenextensively studied for use in lightweight EDLCs. Yet, a major challenge for 3Dcarbon electrodes is the limited ion diffusion rate in their internal spaces.To address this limitation, hierarchically porous 3D structures that provideadditional channels for internal ion diffusion have been proposed. Herein, wereport a new chemical method for the synthesis of an ultralight (9.92 mg/cm3)3D porous carbon foam (PCF) involving carbonization of a glutaraldehydecross-linked chitosan aerogel in the presence of potassium carbonate. Electronmicroscopy images reveal that the carbon foam is an interconnected networkof carbon sheets containing uniformly dispersed macropores. In addition,Brunauer–Emmett–Teller measurements confirm the hierarchically porousstructure. Electrochemical data show that the PCF electrode can achieve anoutstanding gravimetric capacitance of 246.5 F/g at a current density of 0.5 A/g,and a remarkable capacity retention of 67.5% was observed when the currentdensity was increased from 0.5 to 100 A/g. A quasi-solid-state symmetricsupercapacitor was fabricated via assembly of two pieces of the new PCF andwas found to deliver an ultra-high power density of 25 kW/kg at an energydensity of 2.8 Wh/kg. This study demonstrates the synthesis of an ultralight andhierarchically porous carbon foam with high capacitive performance.

Graphical Abstract

Publisher

Tsinghua University Press

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