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Enhanced Specific Capacitance of an Electrophoretic Deposited MnO2-Carbon Nanotube Supercapacitor
Patin Tagsin,Pawinee Klangtakai,Viyada Harnchana,Vittaya Amornkitbamrung,Samuk Pimanpang,Pisist Kumnorkaew 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.71 No.12
MnO2 and MnO2-carbon nanotubes (CNT) composite films were grown directly on stainless- steel substrates using an electrophoretic process employing supercapacitor electrodes. An electrophoretic MnO2 film with a nanoplate-like structure was observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Supercapacitor performance was studied using cyclic voltammetry (CV), charge-discharge (CD) and electrochemical impedance spectroscopy (EIS). The specific capacitance (SC) of the electrophoretic MnO2 film was 60 F/g at 1 A/g, with a 38.33% retention of the initial SC values after 1000 cycles. The low SC value of the MnO2 films was attributed to the high series and charge-transfer resistances of 1.70 and 3.20, respectively. The MnO2-CNT composites with the addition of 0.04, 0.06 and 0.08 g CNT to the electrophoretic MnO2 film were found to greatly increase the SC to 300, 206 and 169 F/g at 1 A/g, respectively. The series and charge-transferred resistances of MnO2-CNT composite films decreased to 1.38 - 1.52 and 2.62 - 2.86 , respectively. The SC improvement of the composite electrodes was attributed to presence of two active storage materials (MnO2 and CNT), a high film specific surface area and electrical conductivity.
Patin Tagsin,Pawinee Klangtakai,Viyada Harnchana,Samuk Pimanpang,Vittaya Amornkitbamrung 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.12
MnO2 films were hydrothermally grown directly onto stainless-steel substrates and used as supercapacitor electrodes. MnO2 with a cube-like structure was observed by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The measured sizes of the cubes were in the range of 270 − 820 nm. The specific capacitance (SC) of the 5-hour hydrothermallygrown MnO2 films was 20.2 F/g, which was slightly higher than that of the 3-hour films (13.8 F/g). The low values of the SC of the hydrothermally-deposited MnO2 films are attributed to their high series resistances of 1.73 − 2.06 measured by using electrochemical impedance spectroscopy. However, the specific capacitance was greatly increased, up to 226 F/g, after a polyaniline polymer had been added into the MnO2 hydrothermal reaction, there by producing a composite of the MnO2 and the polyaniline polymer. This SC improvement was attributed to presence of two active materials (polyaniline and MnO2) and the reduction of the electrode series resistance to 0.93 .