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Mwemezi Manasi,Phiri Isheunesu,Bon Chris Yeajoon,Afrifah Vera Afumaa,Afrifah Vera Afumaa,Pyo Myoungho,Hamenu Louis,Madzvamuse Alfred,Lee Kwangse,Ko Jang Myoun,Kim Yong Joo 한국물리학회 2022 Current Applied Physics Vol.40 No.-
Hydroxyl terminated poly(dimethylsiloxane) (PDMS-HT) is used as an electrolyte additive in electrolyte systems containing 1 M LiPF6 in EC:DMC (ratios 1:9; 3:7; 4:6 and 1:1 v/v) to enhance the cycle performance of lithiumion batteries. Adding a small amount of PDMS-HT to the standard LIB electrolyte leads to improved specific capacity as well as improved capacity retention over prolonged cycles. There is also a slight increase in Li+ ion conductivity when PDMS-HT is added. Also, the PDMS-HT additive allows the formation of a more stable solid electrolyte interface (SEI) layer that enables the LIB cells to be cycled for longer cycles with minimal capacity fading. This combination of improved ionic conductivity and stable SEI layer formation due to the PDMS-HT additive, makes it an excellent candidate for an electrolyte additive for lithium ion batteries.
Rwiza, Mwemezi Johaiven,Oh, Seok-Young,Kim, Kyoung-Woong,Kim, Sang Don Elsevier 2018 CHEMOSPHERE - Vol.195 No.-
<P><B>Abstract</B></P> <P>Corn and rice husks, agro-wastes available in large quantities in Tanzania, were used to remove Pb<SUP>2+</SUP> from aqueous solution. Husks were used in raw form, pyrolyzed form, and chemically modified form. Material characterization was carried out using the BET method, FTIR spectroscopy, SEM, pH<SUB>PZC</SUB>, and cation exchange capacity analysis. Langmuir, Freundlich, Dubinin-Radushkevich (D-R), and Temkin isotherms were used to elucidate Pb<SUP>2+</SUP> sorption mechanisms. The surface area and cation exchange capacity (CEC) of untreated and chemically treated biochars were significantly higher than that of raw husks. Sorption data for Pb<SUP>2+</SUP> for all biosorbents fit the Freundlich and D-R models well with high <I>R</I> <SUP>2</SUP> values. Most of the synthesized biosorbents in this study indicated >90% for Pb<SUP>2+</SUP> removal, with the ZnCl<SUB>2</SUB>-treated corn husk biochar sorption capacities ranking highest in all modeling results. Surface morphological features (e.g., micropores and fissures) and acidic and unsaturated functional groups may have significantly contributed to the observed Pb<SUP>2+</SUP> removal efficiencies.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A multi-level biosorbent synthesis using agro-wastes from Tanzania was conducted. </LI> <LI> Pyrolysis and chemical treatment increase surface area and cation exchange capacity. </LI> <LI> 100% Pb removal by ZnCl<SUB>2</SUB>-treated agro-waste biochars was achieved. </LI> <LI> Low cost agro-wastes are feasible for the removal of heavy metals. </LI> <LI> Four-sorption isotherm modeling confirms high sorption capacity. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Development of Device Control System through Wireless Signal Sensing
Justus Selestine Mwemezi(주스투스 셀레스틴 음웨메지),Lika Long(리카 롱),Dong Min Kim(김동민) 한국통신학회 2021 한국통신학회 학술대회논문집 Vol.2021 No.6
In this research we present device control system through wireless signal sensing that aim at utilizing available Wi-Fi signal to control electronic devices. This research has technical contribution as well as social impact in ensuring livelihood of elderly people.
Mesoporous carbon/Li4Ti5O12 nanoflakes composite anode material lithiated to 0.01 V
Chris Yeajoon Bon,Phiri Isheunesu,Manasi Mwemezi,김상준,Vera Afumaa Afrifah,Louis Hamenu,고장면 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.80 No.-
A composite anode material is fabricated from mesoporous carbon and synthesized Li4Ti5O12 nanoflakesfor application in lithium ion batteries. Li4Ti5O12 is used as a capacity contributing conductive additivebecause of the change in its electronic structure from insulating to metallic as it undergoes lithiation. Cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy areused to analyze the electrochemical properties of the mesporous carbon/Li4Ti5O12 nanoflakes compositematerial, and synergistic results have been confirmed. The composite achieves high specific capacity andexcellent cyclability with a capacity stabilizing at 300 mA h g 1 after 100 cycles at a current density of 175mA g 1 and 200 mA h g 1 after 500 more cycles at a high current density of 500 mA g 1. This researchshows the applicability of using LTO as a conducting agent with significant capacity contribution as acomposite material with anode materials discharged to 0.01 V for high energy storage with fast charge–discharge capability.
Flexible poly(vinyl alcohol)-ceramic composite separators for supercapacitor applications
Chris Yeajoon Bon,Latifatu Mohammed,김상준,Mwemezi Manasi,PHIRI ISHEUNESU,이광세,고장면 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.68 No.-
Electrochemical characterization was conducted on poly(vinyl alcohol) (PVA)-ceramic composite (PVA–CC) separators for supercapacitor applications. The PVA–CC separators were fabricated by mixing various ceramic particles including aluminum oxide (Al2O3), silicon dioxide (SiO2), and titanium dioxide (TiO2) into a PVA aqueous solution. These ceramic particles help to create amorphous regions in the crystalline structure of the polymer matrix to increase the ionic conductivity of PVA. Supercapacitors were assembled using PVA–CC separators with symmetric activated carbon electrodes and electrochemical characterization showed enhanced specific capacitance, rate capability, cycle life, and ionic conductivity. Supercapacitors using the PVA–TiO2 composite separator showed particularly good electrochemical performance with a 14.4% specific capacitance increase over supercapacitors using the bare PVA separator after 1000 cycles. With regards to safety, PVA becomes plasticized when immersed in 6 M KOH aqueous solution, thus there was no appreciable loss in tear resistance when the ceramic particles were added to PVA. Thus, the enhanced electrochemical properties can be attained without reduction in safety making the addition of ceramic nanoparticles to PVA separators a cost-effective strategy for increasing the ionic conductivity of separator materials for supercapacitor applications.
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.