Multi-porous Co3O4 nanoflakes @ sponge-like few-layer partially reduced graphene oxide hybrids: Towards highly stable asymmetric supercapacitors
Journal
Journal of Materials Chemistry A
Journal Volume
5
Journal Issue
24
Pages
12569-12577
Date Issued
2017
Author(s)
Qorbani, M.
Chou, T.-C.
Lee, Y.-H.
Samireddi, S.
Naseri, N.
Ganguly, A.
Esfandiar, A.
Wang, C.-H.
Chen, K.-H.
Moshfegh, A.Z.
Abstract
The controlled growth of metal oxide nanostructures within hierarchically porous conductive carbon-based frameworks is critically important to achieving high volumetric performance and appropriate channel size for energy storage applications. Herein, we grow cobalt oxide (Co3O4) nanoflakes, using a sequential-electrodeposition process, into spherically porous sponge-like few-layer partially reduced graphene oxide (SrGO) synthesized by template-directed ordered assembly. Maximum specific/volumetric capacitances of 1112 F gCo3O4-1 (at 3.3 A gCo3O4-1), 178 F cm-3 (at 2.6 A cm-2), and 406 F gtotal-1 (at 1 A gtotal-1) and sensible rate capability (80% retention by increasing the charge/discharge current from 1 A g-1 to 16 A g-1) are obtained for the Co3O4 nanoflakes@SrGO hybrid electrodes. Besides, an asymmetric supercapacitor is made with the Co3O4[63%]@SrGO[37%] hybrid and activated carbon as a positive and a negative electrode, respectively. Electrochemical results indicate an energy density of 23.3 W h kg-1 at a high power density of 2300 W kg-1 (discharge time of about 42 s) and 62% retention even at a remarkable power density of 36 600 W kg-1 (discharge time of 1.6 s). Moreover, it shows excellent cycling stability with no decay after 20 000 charge/discharge cycles. This performance is attributed to the unique pore-sizes for an ion to channel into the porous structures, conductivity, and mechanical stability of the SrGO framework, which makes it promising for next-generation supercapacitors.
Publisher
Royal Society of Chemistry
Type
journal article