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Latifatu, Mohammed,Bon, Chris Yeajoon,Lee, Kwang Se,Hamenu, Louis,Kim, Yong Il,Lee, Yun Jung,Lee, Yong Min,Ko, Jang Myoun The Korean Electrochemical Society 2018 Journal of electrochemical science and technology Vol.9 No.4
The adhesion strength as well as the electrochemical properties of $LiNi_{0.4}Mn_{0.4}Co_{0.2}O_2$ electrodes containing various conductive carbons (CC) such as fiber-like carbon, vapor-grown carbon fiber, carbon nanotubes, particle-like carbon, Super P, and Ketjen black is compared. The morphological properties is investigated using scanning electron microscope to reveal the interaction between the different CC and the active material. The surface and interfacial cutting analysis system is also used to measure the adhesion strength between the aluminum current collector and the composite film, and the adhesion strength between the active material and the CC of the electrodes. The results obtained from the measured adhesion strength points to the fact that the structure and the particle size of CC additives have tremendous influence on the binding property of the composite electrodes, and this in turn affects the electrochemical property of the configured electrodes.
Latifatu, Mohammed,Park, Jeong Ho,Ko, Jang Myoun,Park, Jongwook Elsevier 2018 Journal of industrial and engineering chemistry Vol.63 No.-
<P><B>Abstract</B></P> <P>Physical mixing of activated carbon (AC) and a quinone derivative, 2,5-bis (pro-2-ny-1-ylamino) cyclohexa-2,5-diene-1,4-dione (coded HBU-281) was used to design a composite electrode for supercapacitors. The process proves to be simple and cost-effective; providing better performance compared to other reported methods. The electrode properties were probed in terms of composite composition, redox behavior, specific capacitance, and cycle life. The capacitance performance of the AC electrode was enhanced due to the extra redox reaction of hydroquinone/quinone couple of HBU-281. The composites recorded higher specific capacitance and excellent cycle stability than the individual electrodes (AC or HBU-281). This excellent performance can be connected to the synergistic contribution of AC facilitating the electron distribution of HBU-281, and making pronounce its redox activity. These findings led to the conclusion that physical mixing of AC and HBU-281 can be adopted to design cheap and excellent composite electrodes for supercapacitor applications.</P>
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>
단신 : 수산화라디칼과 오존에 의한 수중 천연 지방산 분해 제거 연구
( Latifatu Mohammed ),원정하 ( Jung Ha Won ),김용주 ( Yong Joo Kim ),고장면 ( Jang Myoun Ko ),송근한 ( Keun Han Song ),이창훈 ( Chang Hoon Lee ) 한국화학공학회 2013 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.51 No.4
본 연구에서는 수질정화 기술개발을 위하여 수산화라디칼 및 오존 발생기를 이용하여 수중에 존재하는 천연 지방산 분해 제거 연구를 수행하였다. 천연 지방산은 수산화라디칼 및 오존에 의하여 1차 분해반응 형태로 제거되었으며, 천연 지방산의 분해반응에서 수산화라디칼 단독으로 사용하는 것 보다 오존과 함께 사용한 경우 분해 효율을 크게 향상 시킬 수 있음을 알 수 있었다. 또한, 천연 지방산이 수산화라디칼과 오존에 의해 분해되는 화학반응 기구를 제안하였다. In order to purify the waste water containing natural fatty oil, hydroxy radical and/or ozone are used to remove the fatty oil dispersed in the waste water. The fatty oil is decomposed by oxidation reaction through hydroxy radical and ozone, and eliminated as a function of first order reaction. It is clearly confirmed that the fatty oil in waste water can be effectively removed much more in the use of both hydroxy radical and ozone than only hydroxy radical as an oxydant. In addition, the decomposition chemical reaction mechanism of the fatty oil by hydroxy radical and ozone is proposed.
( 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.
( Latifatu Mohammed ),이해수,( Louis Hamenu ),( Jeong Ho Park ),( Kwang Man Kim ),( Jang Myoun Ko ) 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
A quinone-containing conducting additive, 2,5-bis((2-(1H-indol-3-yl) ethyl)amino)cyclohexa 2,5-diene- 1,4-dione (HBU) is synthesized and mixed with activated carbon as an active material to yield a composite supercapacitor electrode. Due to the extra redox reaction of hydroquinone/ quinone couple, the supercapacitor adopting the composite electrode shows the enhancement of the electrochemical specific capacitance up to about 130 F g1 in the scan range of 100-1000 mV s1 and over the repeated redox processes for 1000 cycles at 100 mV s1, compared to the case of activated carbon electrode alone (about 100 F g1). The composite with the HBU is also electrochemically stable in the charge/discharge process and thereby can be highly recommended for supercapacitor electrode additive.
Latifatu Mohammed,Bismark Boating,Manasi Mwemezi,Louis Hamenu,Alfred Madzvamuse,Alex Nyarko,Mutala Mohammed,William Oduro,Francis Boateng Agyenim,이용민,고장면 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.11
Polyolefin separators are inherently hydrophobic and thermally unstable, contributing to poor cycle performance and high thermal shrinkage, respectively, which can shorten cycle life. Herein, a high-performance supercapacitor based on a composite separator made from nano-Al2O3/PVDF-coated on polyethylene (PE) polyolefin substrate was prepared using a low-cost casting (stir-dip-coat-dry) technique and an electrolyte containing 1M EMI-BF4 salt in EC : EMC:DMC (1 : 1 : 2 vol%) is reported. The results show that integration of nano-Al2O3 in the PVDF matrix contributes to a large interactive surface area that attenuates interfacial energy at the separator-electrolyte boundary and improves porosity as well as the overall performance. The filler also enhances high mechanical anchoring onto the PE substrate, contributing to the overall physical and electrochemical properties of the separator. These modified PE separators with porous microstructure demonstrate superior electrolyte wettability (88%), stable electrochemical performance, and high cycle stability superior to analogous cells with commercial separators. The pair of coated modified separators with the 1M EMI-BF4 modified electrolyte registered a high ionic conductivity value of 2.23mS/cm. This facile technique is scalable for separator-electrolyte design and is attractive for low-cost supercapacitor manufacturing which is safe and fast charging.
( Latifatu Mohammed ),박정호,고장면 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0
Composite electrodes composed of activated carbon and 1,4-dihydoxynapthalene derivatives were prepared as electrode material for supercapacitors. The synthesized HBU-551 and HBU-552 were mixed separately with activated carbon as an additive to enhance electrochemical capacitance. HBU-551 and HBU-552 showed electrochemical capacitance of about 216 F/g and 213 F/g in 1 M H2SO4 respectively compared to just the activated carbon. The composite electrodes were electrochemically stable in the charge/discharge process and therefore highly recommended for supercapacitor electrodes.
( Latifatu Mohammed ),박정호,고장면,박종욱 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0
A composite electrode consisting of activated carbon and quinine derivative (HBU-551) was probed in different hydrogen ion conducting electrolytes. The electrochemical performances of the composite electrode in the electrolytes were investigated by cyclic voltammometry (CV), electrochemical impedance spectroscopy (EIS) and charge-discharge. The different hydrogen ion conducting electrolytes with different anion sizes induced different electrochemical properties in the composite electrodes agreeing with their ionic conductivity. The specific capacitance is in the order of H2SO4>H3PO4>HCL>NH4Cl at a potential range of -0.2-0.8(VvsAg/AgCl).
Poly(acrylonitrile) 부직포 분리막에 코팅된 하이드로겔 고분자 전해질을 포함하는 활성탄 수퍼커패시터 특성
모하메드라티파투 ( Mohammed Latifatu ),고장면 ( Jang Myoun Ko ),이영기 ( Young Gi Lee ),김광만 ( Kwang Man Kim ),조정대 ( Jeong Dai Jo ),장윤석 ( Yun Seok Jang ),유정준 ( Jung Joon Yoo ),김종휘 ( Jong Huy Kim ) 한국화학공학회 2013 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.51 No.5
6M KOH 수계 전해액에 potassium poly(acrylate) (PAAK)를 3 wt% 포함시켜 제조한 하이드로겔을 poly(acrylonitrile)부직포 분리막에 코팅하고, 이를 활성탄 수퍼커패시터의 분리막 및 전해질로 사용하여 수퍼커패시터의 고율특성 향상을 시도하였다. 이 분리막 및 전해질은전자현미경 관찰 결과 PAAK 하이드로겔이 부직포의 표면기공에 균일하게 코팅되어 있으며, 24일 동안 하이드로겔의 합습도가 230% 이상으로 균일하게 유지되었고, 6 M KOH 전해액을 사용한 경우(3.6×10-2 S cm-1)보다 약간 낮은 2.9×10-2 S cm-1의 이온전도도를 나타내었다. 활성탄을 활물질로 사용한 대칭형 수퍼커패시터에 이 분리막 및 전해질을 채택한 경우 사이클릭볼타메트리 시험에서 1000 mV s-1의 고속스캔 조건에서도 27 F g-1 이상의 높은 비축전용량과 1000 사이클 경과후에도 97% 이상의 유지율을 나타내는데, 이는 부직포 상에 코팅된 PAAK 하이드로겔 전해질이 활성탄 전극과 부직포 분리막 사이에서 강력한 계면밀착을 유지할 수 있기 때문이다. A hydrogel electrolyte consisting of potassium poly(acrylate) (PAAK) (3 wt%) in 6 M KOH aqueous solution is coated on poly(acrylonitrile) nonwoven separator to examine high-rate characteristics of activated carbon supercapacitor adopting the separator. The hydrogel is homogeneously coated on the surface pores of the nonwoven separator. The electrolyte uptake of the PAAK hydrogel maintains for 24 days higher than 230% and the coated separator shows slightly lower ionic conductivity (2.9×10-2 S cm-1) than that (3.6×10-2 S cm-1) of using 6 M KOH only. The activated carbon supercapacitor adopting the coated separator shows a specific capacitance higher than 27 F g-1 at 1000 mV s-1 and a retention ratio higher than 97% after the 1000th cycle. This is due to strong interfacial contact of coated hydrogel electrolyte between the activated carbon electrode and the nonwoven separator.