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Supercapacitive properties of RuO2 and Ru-Co mixed oxide deposited on single-walled carbon nanotube
( Hu Mengyang ),( Alfred Madzamuse ),( Louis Hamenu ),( Latifatu Mohammed ),이해수,( Kwang Man Kim ),( Jang Myoun Ko ) 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
Composite electrodes for redox supercapacitor were prepared potentiodynamically by the deposition of RuO2 and the co-deposition of Ru-Co mixed oxide on the surface of single-walled carbon nanotube. Electrode of Ru-Co mixed oxide, in which Ru(13.13 wt%) and Co(2.89 wt%) were deposited on the carbon nanotube, exhibited a similar specific capacitance(~ 620 F g-1) with RuO2 electrode at a low potential scan rate(10 mV s-1), but showed a superior one (570 F g-1) at a high scan rate(500 mV s-1) than that of RuO2(475 F g-1). Such increase in the specific capacitance at high scan rate by the co-deposition of Ru and Co species was due to the structural support of Co species to provide the electronic conduction through Ru species.
Hu, Mengyang,Park, Jeong Ho,Lee, Kwang Se,Ko, Jang Myoun The Korean Electrochemical Society 2019 Journal of electrochemical science and technology Vol.10 No.2
A derivative of 1,4-Naphthoquinone coded HBU671 was synthesized and used in addition to activated carbon as composite electrode for supercapacitor application. From the electrochemical properties analysis, a specific capacitance of about $300F\;g^{-1}$ exhibited almost two times of that of activated carbon at a scan rate of $100mV\;s^{-1}$ and a potential window of - 0.2 - 1V. This improvement is due to the inherent redox reaction in HBU671. Cycle test also proved that this composite is still stable even after 1000 cycle within the applied potential window and it is highly recommended for practical application.
Supercapacitive properties of electrodeposited RuO2 electrode in acrylic gel polymer electrolytes
( Hu Mengyang ),( Alfred Madzamuse ),이해수,( Louis Hamenu ),( Latifatu Mohammed ),( Won Il Cho ),( Young-gi Lee ),( Kwang Man Kim ),( Jang Myoun Ko ) 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
Hydrous ruthenium oxide (RuO2) is prepared by electrodeposition on a platinum substrate and its supercapacitive properties are characterized adopting acrylic gel polymer electrolytes, such as poly(acrylic acid) (PAA), potassium polyacrylate (PAAK), and poly(2-acrylamido-2-methyl -1-propanesulfonic acid) (PAMPS). The electrodeposited hydrous RuO2 exhibits an amorphous compact stratified morphology with a higher loading (0.15 mg cm-2) than that of a previous report, and shows broad redox peaks on both cathodic and anodic scans in the cyclic voltammetry. In particular, the RuO2 electrode for supercapacitor adopting the PAMPS electrolyte shows the highest specific capacitance of 642 F g-1 at 20 mV s-1. This is due to the efficient utilization of active RuO2 species and greater proton accommodation toward the negative oxygen sites of PAMPS's side chain. In addition, it is possible to improve sustainability against high-rate current with the RuO2 electrode with the PAMPS electrolyte, due to the crosslinks of the gel electrolyte, which support the mechanical strength.
다공성 Glass Fiber 부직포가 보강된 염기 계 겔 전해질을 포함한 초고용량 캐폐시터의 전기적 특성
( Hu Mengyang ),( Latifatu Mohammed ),우종서,고장면 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0
본 연구에서는 초 흡수성 고분자인 Potassium Acrylic acid 에 9M KOH-H2O를 첨가하여 제조한 염기 계 겔 전해질(APGE) Fig. 1를 다공성 유리섬유에 함침하여 초고용량 케폐시터에 적용할 수 있는 고분자 겔 전해질 복합체를 제조하였다. 케폐시터의 전기 화학적 특성을 확인하기위해 AC 임피던스(Nyquist plot , Bode plot)로 이온전도도와 이온응답속도를 측정하였고 Cyclic voltammetry 와 Charge-Discharge 를 통해서 용량을 확인 할 수 있었다. 그리고 APGE의 형태와 구성 성분을 확인하기 위해 주사전자현미경(SEM) 그리고 EDX 사용하였다. 9MKOH-H2O와 조성이 다른 APGE 전해질로 제조한 캐패시터와의 비교를 통하여 전해질의 누액에 대한 안정성을 확인하였다. 2.0% APGE의 이온전도도는 10 -1S/cm 정도로 측정 되었고 이온응답속도는 2.72 sec를 나타내었다. 본 연구에서 9M KOH H2O를 전해질과 APGE는 비슷한 이온전도도와 용량 값을 나타내었다. 2.0% APGE가 사용된 캐폐시터의 Cyclic voltammetry로 환산된 용량은 209F/g 이었고 충 방전기로 환산된 용량은 전류밀도 0.5 mA에서 237F/g 이었다.
Lithium modified silica as electrolyte additive for lithium secondary batteries
Latifatu, Mohammed,Hu, Mengyang,Kim, Sang Jun,Bon, Chris Yeajoon,Kang, Chiwon,Cho, Won Il,Ko, Jang Myoun Elsevier 2018 Solid state ionics Vol.319 No.-
<P><B>Abstract</B></P> <P>Lithium sulfonyl silica (LSS) was synthesized by replacing the surface H group in fumed silica with (CH<SUB>2</SUB>)<SUB>3</SUB>SO<SUB>3</SUB>Li and adopted as electrolyte additive for lithium ion battery. 3 wt% of the synthesized particles in 1 M LiPF<SUB>6</SUB> (EC/DMC = 1:1) showed improved ionic conductivity and better potential stability over the pristine electrolyte. The discharge capacity of the LiCoO<SUB>2</SUB>/graphite is particularly enhanced with the addition of LSS at higher C-rates due to the enhanced ionic conductivity at room temperature. The LiCoO<SUB>2</SUB>/graphite cells using 1.0 M LiPF<SUB>6</SUB>/EC/DMC (1: 1) and 1.0 M LiTFSI/EC/DMC (1: 1) with LSS also showed superior performance for the self-discharge test carried out at 45 °C for 200 days. These positive impacts of LSS on LiCoO<SUB>2</SUB>/graphite cells warrant its use in lithium ion batteries.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Lithium sulfonyl silica (LSS) was synthesized and used as an electrolyte additive in Li-ion Battery. </LI> <LI> The discharge capacity of the LiCoO<SUB>2</SUB>/graphite is enhanced at higher C-rates. </LI> <LI> The Li-ion cells with the LSS showed superior performance at higher temperature. </LI> </UL> </P>
Louis Hamenu,Alfred Madzvamuse,Mengyang Hu,Latifatu Mohammed,Chris Yeajoon Bon,김상준,조원일,박종욱,고장면 한국물리학회 2017 Current Applied Physics Vol.17 No.12
Supercapacitors provide us with enormous power output for energy storage. Their energy output however still remains quite low compared to other energy storage materials like the batteries. This paper reports a highly stable liquid electrolyte which is composed of mixtures of 1-ethyl-3-methylimidazolium tetrafluoroborate(EMIBF4) ionic liquid with highly stable lithium bis(oxalate)borate LiBOB/acetonitrile( ACN). The electrolytes display remarkable supercapacitive performance at a high voltage of 3 V. The electrochemical impedance spectroscopy shows that EMIBF4 helps to reduce the bulk resistance and charge transfer resistance across the electrode surfaces by facilitating high ionic diffusions across the electrode/electrolyte interface. The high stability and high ionic conductivity of the electrolytes reflected in the good cycling performance tests at 2.8 V with a maximum delivery capacitance of 19.5Fg-1 after 1000cycles at a high scan rate of 200 mVs-1.
이해수,( Louis Hamenu ),( Latifatumohammed ),( Hu Mengyang ),( Alfred Madzamuse ),( Ji Hyun Nam ),( Kwang Man Kim ),( Jang Myoun Ko ) 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
Polyaniline (PAn) electrode for a supercapacitor is prepared by electrodepositing on a platinum substrate. Its supercapacitive properties are characterized after adopting acrylic gel polymer electrolytes, such as poly(acrylic acid) (PAA), potassium polyacrylate (PAAK), and poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS). The electrodeposited PAn (ePAn) exhibits a network structure compactly connected with particles or particle aggregates to yield a porous morphology with an average pore size of 4 μm. The cyclic voltammogram of the ePAn electrode shows redox pair peaks on both cathodic (around 0.2 V) and anodic scans (around 0.1 V vs. Ag/AgCl) at low scan rates, but the redox peak potentials shift to give a higher potential difference at high scan rates, implying higher polarization. Except for the H<sub>2</sub>O/PAMPS electrolyte, the ePAn supercapacitor that adopts the acrylic gel polymer electrolytes exhibits comparable specific capacitance of 400-500 F g<sup>-1</sup>, even at high scan rates, due to specific interactions between the H<sub>2</sub>SO<sub>4</sub> solvent molecules and acrylic polymers.
( Louishamenu ),( Latifatu Mohammed ),이해수,( Alfred Madzamuse ),( Hu Mengyang ),( Kwang Man Kim ),( Jang Myoun Ko ) 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
In this work, lithium-modified silica nanosalt (Li202) is solution-synthesized and used as a gel-forming additive in 1.5 M tetraethylammonium tetrafluoroborate (TEABF4)/acetonitrile (ACN) electrolyte solution for the supercapacitor with activated carbon electrode. The electrochemical properties of the supercapacitor adopting the Li202 (5 wt.%) are investigated using linear sweep voltammetry, cyclic voltammetry, and complex impedance spectroscopy. By the addition of the Li202, the electrochemical stability of the electrolyte is improved over 4.0 V (cor responding to the current density below 0.6 mA cm-2) and higher specific capacitances at the scan rates of 10-500 mV s-1 are obtained. Thus, the Li202 can be considered as a promising electrolyte additive to enhance the supercapacitive properties of activated carbon electrode.
( Latifatu Mohammed ),이해수,( Louis Hamenu ),( Alfred Madzamuse ),( Hu Mengyang ),( Kwang Man Kim ),( Jang Myoun Ko ) 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
Sulfonated polypropylene (S-PP) is prepared by sulfuric acid-acetone aldol condensation reaction of polypropylene (PP) separator to yield hydrophilic separator surface with a moderate amount of -SO3H groups. Activated carbon supercapacitor is also fabricated adopting the S-PP separator coated with potassium polyacrylate (PAAK) hydrogel polymer electrolyte. As a result, the hydrophilic surface of S-PP separator involves better physical and electrochemical properties such as decrease in contact angle, improvements of wettability, electrolyte uptake, and ionic conductivity to give higher specific capacitance and long cycle-life.
이해수,( Louishamenu ),( Latifatumohammed ),( Yeo Il Yoon ),( Alfred Madzamuse ),( Hu Mengyang ),( Jang Myoun Ko ) 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
Prepared are three types of composite supercapacitor electrode, such as electroactive polyaniline (PAN), PAN/multi-walled carbon nanotube (CNT), and PAN/CNT/RuO<sub>2</sub>. Cyclic voltammetry was performed to investigate the supercapacitive properties of these electrodes in an electrolyte solution of 1.0M H<sub>2</sub>SO<sub>4</sub>. The PAN/CNT/RuO<sub>2</sub> electrode showed the highest specific capacitance at all scan rates (e.g., 441 and 392 F g<sup>-1</sup> at 100 and 1,000 mV s<sup>-1</sup>, respectively). In cycle performance, however, the PAN/CNT electrode demonstrated the best capacitance retention (66%) at 104th cycle.