Browsing by Author "Ko, J.M."
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Item Effect of Morphologically Different Conductive Agents on the Performance of Silicon Anode in Lithium‐Ion Batteries(ChemistrySelect, 2018-10) Madzvamuse, A.; Hamenu, L.; Mohammed, L.; Ko, J.M.The performance of electrochemical electrodes, is largely dependent on the extent of efficient electrical contacts between particles, and secondly, between the current collector and the particles, amongst other factors. We report on the electrical conductivity of silicon anode electrodes that have been prepared by using conductive agents with different morphological properties. Super P® Li (SP), VGCF®‐H vapor grown carbon fibers (VGCF), and their mixture were incorporated separately into the anode electrode to observe their distinctive resultant performance. The morphological characterization was done using scanning electron microscopy whilst the electrochemical properties of the prepared electrodes were characterized by electrical resistivity test, cyclic voltammetry, charge/discharge tests and electrochemical impedance spectroscopy. The combination of VGCF®‐H and Super P® Li, results in improved performance of the anode, due to their synergistic interactions which reduce the effects encountered during the failure of the silicon anode electrode caused by large volume changes. These findings unlock new opportunities for the exploration and development of other morphologically useful conductive agents to improve silicon anode in lithium ion batteries.Item Effects of novel benzotriazole based zwitterionic salt as electrolyte additive for lithium ion batteries(Current Applied Physics, 2019-10-20) Hamenu, L.; Phiri, I.; Bon, C.Y.; Kim, S.; Mwemezi, M.; Madzvamuse, A.; Kim, S.H.; Ko, J.M.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.Item Enhanced electrolyte performance by adopting Zwitterionic lithium-silica sulfobetaine silane as electrolyte additive for lithium-ion batteries(Materials Chemistry and Physics, 2019-12-25) Hamenu, L.; Phiri, I.; Bon, C.Y.; Mwemezi, M.; Madzvamuse, A.; Park, J.H.; Lee, K,S.; Ko, J.M.; Lu, Y.Zwitterionic lithium-silica sulfobetaine silane is fabricated by first synthesizing zwitterion sulfobetaine silane, grafting it onto hydrophilic silica to form silica sulfobetaine silane, and then lithiating the silica sulfobetaine silane. The resultant lithium-silica sulfobetaine silane additive is used as a liquid electrolyte additive in lithium-ion batteries with varying weight percentages in 1 M LiPF6 (ethylene carbonate/dimethyl carbonate ¼ 1:1). The electrolytes with the lithium-silica sulfobetaine silane shows higher ionic conductivities (1.92 × 10-2 S cm-1 at RT and 1.62 × 10-3 S cm-1 at -20 oC) and greater electrochemical stability (anodic limit at ~5.5 V vs. Li/Liþ) than the pure electrolyte (anodic limit at ~4.6 V vs. Li/Liþ). The discharge capacity of the lithium nickel cobalt manganese oxide/graphite cell is improved at higher C-rates with the addition of lithium-silica sulfobetaine silane due to increased ionic conductivity. The lithium nickel cobalt manganese oxide/graphite cells with the lithium-silica sulfobetaine silane additive also show stable cycling performance. These findings warrant the use of lithium-silica sulfobetaine silane as an electrolyte additive in lithium-ion batteries.Item Mesoporous carbon/Li4Ti5O12 nanoflakes composite anode material lithiated to 0.01 V(Journal of Industrial and Engineering Chemistry, 2019-09-01) Hamenu, L.; Bon, C.Y.; Isheunesu, P.; Mwemezi, M.; Kim, S.; Afrifah, V.A.; Ko, J.M.A composite anode material is fabricated from mesoporous carbon and synthesized Li4Ti5O12 nanoflakes for application in lithium ion batteries. Li4Ti5O12 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/Li4Ti5O12 nanoflakes composite material, and synergistic results have been confirmed. The composite achieves high specific capacity and excellent cyclability with a capacity stabilizing at 300 mA h g 1 after 100 cycles at a current density of 175 mA g 1 and 200 mA h g 1 after 500 more cycles at a high current density of 500 mA g 1. 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 0.01 V for high energy storage with fast charge– discharge capability.Item Structural Effect of Conductive Carbons on the Adhesion and Electrochemical Behavior of LiNi0.4Mn0.4Co0.2O2 Cathode for Lithium Ion Batteries(Journal of Electrochemical Science and Technology, 2018-12) Latifatu, M.; Bon, C.Y.; Lee, K.S.; Hamenu, L.; Kim, Y.I.; Lee, Y.J.; Lee, Y.M.; Ko, J.M.The adhesion strength as well as the electrochemical properties of LiNi Mn Co O 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 micro- scope 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 com- posite 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.