Flexible poly(vinyl alcohol)-ceramic composite separators for supercapacitor applications

Bon, Chris Yeajoon,Mohammed, Latifatu,Kim, Sangjun,Manasi, Mwemezi,Isheunesu, Phiri,Lee, Kwang Se,Ko, Jang Myoun THE KOREAN SOCIETY OF INDUSTRIAL AND ENGINEERING 2018 JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY -S Vol.68 No.-

<P><B>Abstract</B></P> <P>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 (Al<SUB>2</SUB>O<SUB>3</SUB>), silicon dioxide (SiO<SUB>2</SUB>), and titanium dioxide (TiO<SUB>2</SUB>) 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–TiO<SUB>2</SUB> 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 6M 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.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Mesoporous carbon/Li₄Ti₅O₁₂ nanoflakes composite anode material lithiated to 0.01V

Bon, Chris Yeajoon,Isheunesu, Phiri,Mwemezi, Manasi,Kim, Sangjun,Afrifah, Vera Afumaa,Hamenu, Louis,Ko, Jang Myoun Elsevier 2019 Journal of industrial and engineering chemistry Vol.80 No.-

<P><B>Abstract</B></P> <P>A composite anode material is fabricated from mesoporous carbon and synthesized Li<SUB>4</SUB>Ti<SUB>5</SUB>O<SUB>12</SUB> nanoflakes for application in lithium ion batteries. Li<SUB>4</SUB>Ti<SUB>5</SUB>O<SUB>12</SUB> is used as a capacity contributing conductive additive because of the change in its electronic structure from insulating to metallic as it undergoes lithiation. Cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy are used to analyze the electrochemical properties of the mesporous carbon/Li<SUB>4</SUB>Ti<SUB>5</SUB>O<SUB>12</SUB> nanoflakes composite material, and synergistic results have been confirmed. The composite achieves high specific capacity and excellent cyclability with a capacity stabilizing at 300mAhg<SUP>−1</SUP> after 100 cycles at a current density of 175mAg<SUP>−1</SUP> and 200mAhg<SUP>−1</SUP> after 500 more cycles at a high current density of 500mAg<SUP>−1</SUP>. This research shows the applicability of using LTO as a conducting agent with significant capacity contribution as a composite material with anode materials discharged to 0.01V for high energy storage with fast charge–discharge capability.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Composite anode material is fabricated from mesoporous carbon and LTO nanoflakes. </LI> <LI> Mesoporous has high capacity but suffers from decreased conductivity. </LI> <LI> LTO is used as a conductive active material as it becomes metallic under 1V. </LI> <LI> The composite material exhibits electrochemical synergy when lithiated to 0.01V. </LI> <LI> The composite material shows increased capacity, rate capability, and cycle life. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

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.

Structural Effect of Conductive Carbons on the Adhesion and Electrochemical Behavior of LiNi_0.4Mn_0.4Co_0.2O₂ Cathode for Lithium Ion Batteries

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.

Effects of novel benzotriazole based zwitterionic salt as electrolyte additive for lithium ion batteries

Isheunesu Phiri,Chris Yeajoon Bon,Sang Jun Kim,Manasi Mwemezi,Louis Hamenu,Alfred Madzvamuse,Sang Hern Kim,Jang Myoun Ko 한국물리학회 2020 Current Applied Physics Vol.20 No.1

A novel zwitterionic lithium-benzotriazole sulfobetaine is fabricated by grafting 1,3– propanesultone onto benzotriazole and then lithiating it. The resultant lithium-benzotriazole-sulfobetaine additive is used as an electrolyte additive in lithium ion batteries in 1M LiPF6 (ethylene carbonate/dimethyl carbonate=1:1). The electrolytes with the lithium-benzotriazole sulfobetaine shows higher ionic conductivities (2.18 × 10−2 S cm−1) compared to the bare electrolyte (1.07 × 10−2 S cm−1) and greater electrochemical stability (anodic limit at ~5.5 V vs. Li/Li+) than the pure electrolyte (anodic limit at ~4.6 V vs. Li/Li+). The discharge capacity of the lithium cobalt oxide/graphite cells is improved at higher C-rates with the addition of lithium-benzotriazole sulfobetaine due to increased ionic conductivity. The lithium cobalt oxide/graphite cells with the lithiumbenzotriazole sulfobetaine additive also show stable cycling performance. These findings warrant the use of lithium-benzotriazole sulfobetaine as an electrolyte additive in lithium ion batteries.

Hydroxyl terminated Poly(dimethylsiloxane) as an electrolyte additive to enhance the cycle performance of lithium-ion batteries

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.

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>

Lithium Bis(oxalate)borate as an Electrolyte Salt for Supercapacitors in Elevated Temperature Applications

Madzvamuse, Alfred,Hamenu, Louis,Mohammed, Latifatu,Bon, Chris Yeajoon,Kim, Sang Jun,Park, Jeong Ho,Ko, Jang Myoun The Korean Electrochemical Society 2017 Journal of electrochemical science and technology Vol.8 No.4

The electrolyte plays one of the most significant roles in the performance of electrochemical supercapacitors. Most liquid organic electrolytes used commercially have temperature and potential range constraints, which limit the possible energy and power output of the supercapacitor. The effect of elevated temperature on a lithium bis(oxalate)borate(LiBOB) salt-based electrolyte was evaluated in a symmetric supercapacitor assembled with activated carbon electrodes and different electrolyte blends of acetonitrile(ACN) and propylene carbonate(PC). The electrochemical properties were investigated using linear sweep voltammetry, cyclic voltammetry, galvanostatic charge-discharge cycles, and electrochemical impedance spectroscopy. In particular, it was shown that LiBOB is stable at an operational temperature of $80^{\circ}C$, and that, blending the solvents helps to improve the overall performance of the supercapacitor. The cells retained about 81% of the initial specific capacitance after 1000 galvanic cycles in the potential range of 0-2.5 V. Thus, LiBOB/ACN:PC electrolytes exhibit a promising role in supercapacitor applications under elevated temperature conditions.

Pushing the limits of lithium bis(oxalate)borate/acetonitrile using 1- ethyl-3-methylimidazolium tetrafluoroborate for supercapacitors

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.