Anionic dopant–dispersants for synthesis of polypyrrole coated carbon nanotubes and fabrication of supercapacitor electrodes with high active mass loading† Yeling Zhu, Kaiyuan Shi and Igor Zhitomirsky * A conceptually new approach has been developed for the fabrication of composite polypyrrole (PPy)– multiwalled carbon nanotube (MWCNT) electrodes for electrochemical supercapacitors (ESs). The approach is based on the use of pyrocatechol violet (PV), eriochrome cyanine R (ECR) and acid fuchsin (AF) dyes as dispersants for MWCNTs and dopants for PPy polymerization. Testing results showed excellent electrochemical performance of the composite electrodes at high active mass loadings. The composite electrodes showed superior capacitance retention at high scan rates, compared to pure PPy electrodes. The comparison of the experimental data for the ES electrodes, prepared using different dyes, provided insight into the influence of their structure and functional groups on the composite microstructure and electrochemical performance. The use of ECR as a dispersant for MWCNTs and dopants for PPy allowed the fabrication of PPy coated MWCNTs. The fabrication method is simple and suitable for mass production. This new finding opens up a new and promising strategy for the fabrication of efficient ES electrodes and devices. The PPy coated MWCNTs were used for the fabrication of electrodes with a specific capacitance of 2.430–4.798 F cm 2 in the scan rate range of 2–100 mV s 1 for active mass loading of 18 mg cm 2 . The ES cells showed high capacitance at different charge discharge rates and good cycling stability. The ES cells and modules showed promising performance for practical applications. 1 Introduction Polypyrrole (PPy) is currently under intensive investigation for energy storage in electrochemical supercapacitors (ES). 1 The interest in PPy is attributed to high specic capacitance, high electrical conductivity and low cost of this material. 2 Recent studies highlighted the importance of the fabrication of efficient supercapacitor electrodes with high active mass loading and high active material to current collector mass ratio. 3 However, it is challenging to achieve high capacitance, good capacitance retention at high charge–discharge rates and cyclic stability for electrodes with mass loadings of 10–20 mg cm 2 , which are required for many practical applications. 3,4 The specic capaci- tance of PPy electrodes decreased with increasing PPy mass loading. 5 In this case the ES electrodes did not benet from the increasing mass of the active material. Another problem, limiting the application of PPy in ES, is poor cycling stability. 6 Many efforts have been made to improve electrochemical performance of PPy by the development of efficient dopants. It was found that the size and shape of PPy particles and elec- trochemical performance of PPy 7,8 were inuenced by the structure of the anionic dopants. Aromatic dopants promoted preferred orientation of the pyrrole ring parallel to the electrode or growth surface and enhanced PPy conductivity. 9 The use of large dopant molecules offers the advantage of their reduced movement during the charge–discharge process and reduced PPy swelling. 10 Moreover, large polyaromatic molecules 11 provided improved cycling stability of the ES electrodes. The increase in the size and charge to mass ratio of the dopant molecules resulted in reduced size of the PPy particles and increased capacitance. 12 However, poor capacitance retention was observed at high charge–discharge rates for electrodes with high PPy mass loading. 12 It was found that cyclic stability of the PPy lms can be improved by the use of multi-charged aromatic anionic dopants. 12 Moreover, anionic dopants, containing several charged groups can be linked to different polymer macromolecules, thus increasing interchain mobility of charge carriers and increasing PPy conductivity. 13 These studies showed that the investigation of new dopants is an important strategy in the development of efficient PPy electrodes. Department of Materials Science and Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4L7, Canada. E-mail: zhitom@mcmaster.ca; Tel: +1-(905)-525-9140 † Electronic supplementary information (ESI) available: Testing results for pure MWCNT electrodes and cells, based on PPy coated MWCNT electrodes. See DOI: 10.1039/c4ta02117g Cite this: J. Mater. Chem. A, 2014, 2, 14666 Received 29th April 2014 Accepted 8th July 2014 DOI: 10.1039/c4ta02117g www.rsc.org/MaterialsA 14666 | J. Mater. Chem. A, 2014, 2, 14666–14673 This journal is © The Royal Society of Chemistry 2014 Journal of Materials Chemistry A PAPER Published on 10 July 2014. Downloaded by McMaster University on 12/08/2014 17:43:57. View Article Online View Journal | View Issue