Electrochemical properties of conductive filler/carbon aerogel composites as electrodes of supercapacitors

doi:10.1016/j.jnoncrysol.2008.06.007

Journal of Non-Crystalline Solids

Volume 354, Issues 40–41, 15 October 2008, Pages 4567-4571

https://doi.org/10.1016/j.jnoncrysol.2008.06.007 Get rights and content

Abstract

Carbon black, multi-walls carbon nanotube (CNT) and vapor grown carbon nano-fiber with different contents were added to the carbon aerogels (CAs) electrodes as conductive fillers to improve their capacitive properties. The results show that maximum capacitance exists when the content of the conductive filler gets to its percolation threshold. CNT is the most ideal conductive filler. The CA with 1 wt% content of CNT has the best electrochemical performance; its specific capacitances are 141.3 F g⁻¹ at 5 mV s⁻¹ and 127.1 F g⁻¹ at 100 mV s⁻¹, 1.4 times and 2.2 times as high as that of CA electrode, respectively.

Introduction

Electrochemical double layer capacitors (EDLCs) are unique energy storage devices and show promise for applications [1], [2], [3], [4]. The capacitance of EDLCs is strongly dependent upon the electrode area, and only those materials which are conductive and inert would be choices for these electrodes. Among the EDLC material candidates, carbon aerogels (CAs) are promising electrode materials due to their interconnected microstructure, high specific surface area, controllable pore structures and high electrical conductivity [5], [6].

Up to now, CA as a novel nanometer size porous amorphous carbon material has developed for nearly 20 years. At first, due to the time-consuming preparation and critical dried conditions, CAs were not in large-scale productions [7]. To solve the problems, new preparation methods were developed [8], [9], [10]. For example, ambient pressure drying preparation of CAs was explored by Wu et al. [11]. It is a cheaper and simpler method and thus improves the chances for large-scale application [12], [13], [14], [15], [16].

In the present work, CAs made by our group [11] were used as EDLCs electrode material. It was found that CAs are ideal materials for EDLCs compared with other electrodes materials [17], [18], [19]. However, related factors that affect the performances of EDLC, such as particle size, binders and conductive fillers, the poorer rate performance in electrode can be ascribed to an increase in the time constant contributed by the inter-particle pore resistance [20]. To improve the rate capability, carbon black (CB), multi-walls carbon nanotube (CNT) and vapor grown carbon nano-fiber (VCF) were chosen as conductive fillers to be added in the active materials. And the electrochemical presentations of conductive fillers with different contents were discussed to determine the optimum content.

Section snippets

Preparation of CAs

According to the predetermined formulations, resorcinol, formaldehyde, deionized water and cetyltrimethylammonium bromide, were mixed by a magnetic stirrer at room temperature and then transferred into a glass vial about 500 ml. The vial was sealed and then was put into a water bath at 75 °C to cure for 1 day and then cure for 4 days at 85 °C. After curing, the gels were directly dried in air at room temperature for 2 days, and then further dried under an infrared lamp with an irradiation

Results

Table 1 summarizes microstructural properties of CA, CB, VCF and CNT by nitrogen adsorption–desorption measurement. It can be seen that they have a dominant mesopore distribution. CA is a typical mesoporous material with high surface area (638 m² g⁻¹) and great mesopore volume (1.00 cm³ g⁻¹). The CAs with a large percentage of mesopores are more suitable to high power supercapacitor applications because the ions transport into the pores more easily [21]. Compared to CA, the BET and

Discussion

The capacitance of EDLC is not only related to the specific area of the active material, but also with the pore size and distribution. Pore size between 1 nm and 20 nm are presumably suitable for electrolyte to be accessed [23]. According to the Tabel.1, VCF and CNT have suitable pore size for electrolyte to be accessed; however the surface areas are negligible. The pore size of CB is unnecessarily large. So the capacitances of VCF, CNT and CB are little (Fig. 1), which means their capacitance

Conclusions

CAs were able to use as electrode material for supercapacitors. Conductive fillers added can improve the respond rate and high power density of CA electrode. Especially the CA/CNT electrode shows the lowest percolation threshold and the best electrochemical performance. The capacitances of CA/CNT-1 are always higher than that of other electrodes. It will be able to deliver the stored energy at higher power.

Acknowledgements

This research was supported by the Project of NNSFC (50472029, 50632040), and the Scientific Foundation of Guangzhou (2007Z2-D2041).

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Electrochemical properties of conductive filler/carbon aerogel composites as electrodes of supercapacitors

Abstract

Introduction

Section snippets

Preparation of CAs

Results

Discussion

Conclusions

Acknowledgements

Electrochim. Acta

J. Power Sources

J. Power Sources

J. Non-Cryst. Solids

J. Non-Cryst. Solids

Carbon

Carbon

NanoStruct. Mater.

Chem. Eng. J.

Carbon

Carbon

J. Power Sources