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Preparation and Characterization of Ruthenium Oxide Based Composite Electrode for Supercapacitor

Author: LiXiang
Tutor: GanWeiPing
School: Central South University
Course: Materials Science
Keywords: oxide ruthenium activated carbon polyaniline polypyrrole specific capacitance
CLC: TM53
Type: PhD thesis
Year: 2012
Downloads: 244
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Abstract

Owing to its irreplaceable advantage with highest specific capacitance and specific energy, as well as the best charge and discharge property, supercapacitor has been considered as one of the new energy storage devices worldwide.Based on Faraday charge and discharge principle, RuO2has been identified as the key electrode material to make high specific capacitance supercapacitors. However, the application of RuO2was limited due to its high cost. Therefore, established on the frontier of the developing technology of supercapacitor electrode materials at home and abroad today, this paper focuses on the effects of RuO2-based electrode prepared with different composite systems and different methods on properties of high specific capacitance supercapaciors, aiming to find the law between its performance and cost. It is far-reaching significant for developing new high specific capacitance supercapacitor and enlarging application rang to figure out how to greatly reduce the cost and give full play to its performance.In this paper, we have studied different technics to prepare RuO2-based composite electrode with different systems, including rotation coating situ thermal decomposition method to prepare RuO2film electrodes, modified traditional colloidal method to prepare RuO2/activated carbon (AC) composite electrode, electrodeposition method to prepare RuO2/polyaniline (PANI) electrode and the combination of thermal decom-position and electrochemical oxide method to prepare RuO2/PANI and RuO2/polypyrrole (PPy) composite electrode. Based on those cases, we haved made further study on the effects of preparation, morphology and microstructure of RuO2composite electrode film doped with AC, PANI and PPy on electrochemical properties of electrodes, and we also optimized the property of specific capacitance, equivalent series resistance and cycle life of the electrode. The major findings of this paper are as follows:1. RuO2film electrode prepared by low cost and rotation si-tu coating thermal decomposition method is proposed for the first time. This method is easy to manipulate with low requirements for devices, and electrodes film has uniform thickness, excellent adhesion and great electrochemical properties, et al. The best comprehensive properties of RuO2film electrodes are obtained when RuO2film electrodes were annealed at260℃for3h. Meanwhile, the film thickness is7.7～8.0μm, adhesion gets18.00MPa, specific capacitance reaches705.3Fg-1and equivalent series resistance (ESR) lows to0.436Ω, and specific capacitance only loses0.32%after1000cycles.2. We firstly proposed a direct coating technology using RuO2/AC composite powders to prepare low cost and well performed RuO2/AC composite electrode. This method solved a series of problems of RuO2/AC composite prepared by traditional colloid method which includes problems such as:1) specific surface of film in electrode formed by coarse grain ruthenium oxide films declines and leads to specific capacitance decrease,2) NaCl generated in the reaction could hardly be eliminated,3) the mechanic tablet technology is used in the electrode preparation, this decreases the adhension between composite material and matrix, and finally makes the composite material spin off the matrix and leads to failure, etc. Direct coating RuO2/AC composite powders method has renovated the low cost and short technology of preparing composite electrode materials.3. The effect of annealing temperature and loading of activated carbon on phase structure and electrochemical properties of RuO2/AC composite electrode is revealed. The result shows that the highest specific capacitance of445Fg-1and excellent charge and discharge performance is obtained when RuO2/AC composite is annealed at240℃for4h. The capacitance decreases and more crystal phases appear when annealing temperature raises to270℃. In addition, study shows that the optimized content of activated carbon is27.65wt.%at which comes the highest specific capacitance of582Fg-1with only10.4%loss of specific capacitance after1000cycles.4. RuO2/PANI composite electrode prepared by electrodeposition and thermal decomposition combination method is explored and optimized. Firstly, as compasion, RuO2/PANI composite electrode has been prepared by electrodeposition method, and its specific capacitance is 474Fg-1, and only loss12%after1000cycles. Next, the composite electrode was prepared by electrodeposition and thermal decomposition combination method. The combination of the two methods can performs the advantages of both two preparations, that is to say, electrodeposition method can obtain high film adhesion, and thermal decomposition save precious metals of RuCl3.nH2O, and the amount of RuCl3.nH2O consumed by coating method is about1/15that of electrodeposition method. PANI particles prepared by combined method are fine and with good interface. The specific capacitance reaches478Fg-1and only loses11%after1000cycles.5. The effect of deposition time, current density and pyrrole monomer concentration on morphology and electrochemical performance of RuO2/PPy electrode prepared by combination method was revealed. The results show that the composite electrode obtains the best properties which specific capacitance reaches486Fg-1and only loses9.8%after1000cycles when deposition time, current density and pyrrole concentration are25min,2.4mA-cm-2and0.20mol·L-1, respectively.

Preparation and Characterization of Ruthenium Oxide Based Composite Electrode for Supercapacitor

Abstract

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