Ingenieria quimica

international journal of hydrogen energy 34 (2009) 4889–4899

Available at www.sciencedirect.com

journal homepage: www.elsevier.com/locate/he

Review

Progress of electrochemical capacitor electrode materials: A review
Yong Zhang*, Hui Feng, Xingbing Wu, Lizhen Wang, Aiqin Zhang, Tongchi Xia, Huichao Dong, Xiaofeng Li, Linsen Zhang
Henan Provincial Key Laboratory of Surface & InterfaceScience, Zhengzhou University of Light Industry, Zhengzhou 450002, China

article info
Article history: Received 16 February 2009 Received in revised form 4 April 2009 Accepted 4 April 2009 Available online 29 April 2009 Keywords: Electrochemical capacitor Electrode materials Review

abstract
The electrode is the key part of the electrochemical capacitors (ECs), so the electrode materialsare the most important factors to determine the properties of ECs. In this paper, the storage principles and characteristics of electrode materials, including carbon-based materials, transition metal oxides and conductive polymers for ECs are depicted briefly. Among them, more work has been done using microporous carbons than with the other materials and most of the commercially available devicesuse carbon electrodes and organic electrolytes. But the composites of pseudocapacitive and carbonaceous materials are promising electrode materials for ECs because of their good electrical conductivity, low cost and high mass density. ª 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.

1.

Introduction

Electrochemical capacitors (ECs), oftencalled super-capacitors, electrical double-layer capacitors (EDLCs), pseudocapacitances, ultracapacitors, power capacitors, gold capacitors or power caches, have attracted worldwide research interest because of their potential applications as energy storage devices in many fields [1,2]. The charge-storage mechanism of these capacitors is predominately due to double-layer (DL) charging effects. Butin general, additional contributions of pseudocapacitance may also be part of the observed capacitance due to the functional groups present on the electrode surface [3]. So referring these capacitors as ECs is more appropriate, which is similar to a battery, they both require two electrodes (anode and cathode), an electrolyte, and a conducting charge path in

order to operate, ECs also have anadditional component, the separator that electrically isolates the two electrodes. These four components are then packaged together and can be used as a conventional capacitor would be, where the main structural difference is that in most EDLCs both the positive and negative electrodes are made of the same material. EDLCs are comprised of many individual cells (parallel or serial) in series to havehigh capacitance and work voltage. Fig. 1 depicts a typical structure model of EDLCs [4]. The primary advantages of ECs are that they can provide high power capability (60–120 s is typical), excellent reversibility (90–95% or higher), and long cycle life (>105). Typically they exhibit 20–200 times larger capacitance per unit volume or mass than conventional capacitors [5,6]. Therefore, a numberof applications now use ECs or are strongly considering them for use, including electric vehicles, digital

* Corresponding author. Tel./fax: þ86 371 63556510. E-mail address: zy@zzuli.edu.cn (Y. Zhang). 0360-3199/$ – see front matter ª 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ijhydene.2009.04.005

4890

internationaljournal of hydrogen energy 34 (2009) 4889–4899

Tab

Sealant

Current collector

Electrolyte

Separator

Electrode

Shell

Fig. 1 – The basic structure model of EDLCs.

communication devices, digital cameras, mobile phones, electric hybrid vehicles, electric tools, pulse laser technique, uninterruptible power supplies for computers, and storage of the energy generated by solar...