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Your search keyword '"Cheruvally, Gouri"' showing total 42 results
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42 results on '"Cheruvally, Gouri"'

39. Effect of mechanical activation process parameters on the properties of LiFePO4 cathode material

Author

Kim, Jae-Kwang, Cheruvally, Gouri, Choi, Jae-Won, Kim, Jong-Uk, Ahn, Jou-Hyeon, Cho, Gyu-Bong, Kim, Ki-Won, and Ahn, Hyo-Jun

Subjects
*LITHIUM cells, *INDUSTRIAL concentration, *CATHODES, *ELECTRODES
Abstract

Abstract: Pure, nano-sized LiFePO4 and carbon-coated LiFePO4 (LiFePO4/C) positive electrode (cathode) materials are synthesized by a mechanical activation process that consists of high-energy ball milling and firing steps. The influence of the processing parameters such as firing temperature, firing time and ball-milling time on the structure, particle size, morphology and electrochemical performance of the active material is investigated. An increase in firing temperature causes a pronounced growth in particle size, especially above 600°C. A firing time longer than 10h at 600°C results in particle agglomeration; whereas, a ball milling time longer than 15h does not further reduce the particle size. The electrochemical properties also vary considerably depending on these parameters and the highest initial discharge capacity is obtained with a LiFePO4/C sample prepared by ball milling for 15h and firing for 10h at 600°C. Comparison of the cyclic voltammograms of LiFePO4 and LiFePO4/C shows enhanced reaction kinetics and reversibility for the carbon-coated sample. Good cycle performance is exhibited by LiFePO4/C in lithium batteries cycled at room temperature. At the high current density of 2C, an initial discharge capacity of 125mAhg−1 (73.5% of theoretical capacity) is obtained with a low capacity fading of 0.18% per cycle over 55 cycles. [Copyright &y& Elsevier]

Published
2007
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40. Effect of Metal Additives (Co and Ni) on the Electrochemical Properties of Lithium/FeS2 Batteries

Author

Choi, Jae Won, Cheruvally, Gouri, Ahn, Jou Hyeon, Kim, Ki Won, and Ahn, Hyo Jun

Abstract

Iron, sulfur and transition metal powders were used as the starting materials to prepare iron disulfide (FeS2) cathode material at room temperature by high energy mechanical alloying. Modified FeS2 were also prepared by incorporation of transition metals like Co and Ni. Li/FeS2 cells with the prepared iron disulfides as cathodes were studied for discharge properties at room temperature using the 0.5M LiTFSI in tetra(ethylene glycol) dimethyl ether (TEGDME). The first discharge capacities of Li/composite FeS2 cell with 5 wt.% Co and 3 wt.% Ni were 571 and 844 mAh/g, respectively, compared to 389 mAh/g for the cell without any additive. The enhanced properties resulted from the better electronic conductivity of the material containing the metallic additive. The initial capacity and cyclic performance were improved when nickel and cobalt were added to prepare the modified iron disulfide.

Published
2007
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41. Novel electrospun poly(vinylidene fluoride-co-hexafluoropropylene)–in situ SiO2 composite membrane-based polymer electrolyte for lithium batteries

Author

Raghavan, Prasanth, Choi, Jae-Won, Ahn, Jou-Hyeon, Cheruvally, Gouri, Chauhan, Ghanshyam S., Ahn, Hyo-Jun, and Nah, Changwoon

Subjects
*POLYELECTROLYTES, *LITHIUM ions, *ELECTRIC batteries, *ELECTROSPINNING
Abstract

Abstract: Composite membranes of poly(vinylidene fluoride-co-hexafluoropropylene) {P(VdF-HFP)} and different composition of silica have been prepared by electrospinning polymer solution containing in situ generated silica. These membranes are made up of fibers of 1–2μm diameters. These fibers are stacked in layers to produce fully interconnected pores that results in high porosity. Polymer electrolytes were prepared by immobilizing 1M LiPF6 in ethylene carbonate (EC)/dimethyl carbonate (DMC) in the membranes. The composite membranes exhibit a high electrolyte uptake of 550–600%. The optimum electrochemical properties have been observed for the polymer electrolyte containing 6% in situ silica to show ionic conductivity of 8.06mScm−1 at 20°C, electrolyte retention ratio of 0.85, anodic stability up to 4.6V versus Li/Li+, and a good compatibility with lithium metal resulting in low interfacial resistance. A first cycle specific capacity of 170mAhg−1 was obtained when the polymer electrolyte was evaluated in a Li/lithium iron phosphate (LiFePO4) cell at 0.1C-rate at 25°C, corresponding to 100% utilization of the cathode material. The properties of composite membrane prepared with in situ silica were observed to be comparatively better than the one prepared by direct addition of silica. [Copyright &y& Elsevier]

Published
2008
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42. Pt-TiO₂ Nanocomposites as Catalysts for Proton Exchange Membrane Fuel Cell: Prominent Effects of Synthesis Medium pH.

Author

Bharti A, Muliankeezhu S, and Cheruvally G

Abstract

Pt-TiO2 nanocomposite catalysts in different Pt:Ti atomic ratios (1:1, 2:1 and 3:1) were synthesized in acidic (pH < 3) and basic (pH >10) medium for oxygen reduction reaction of proton exchange membrane fuel cells. The pH of synthesis medium significantly affected both physicochemical and catalytic properties of Pt-TiO2. Pt-TiO2 prepared in acidic medium exhibited smaller crystallite size, higher specific surface area and more non-stoichiometric titania with higher electrical conductivity as compared to that prepared in basic medium. The oxygen reduction reaction performance from fuel cell polarization curves showed that, Pt-TiO2 catalysts synthesized in acidic medium performed better than those prepared in basic medium. Among the catalysts with varying Pt:Ti atomic ratios, performance decreased in the order 3:1 > 2:1 > 1:1. Among all, Pt:Ti 3:1-A was found to exhibit better fuel cell performance as ORR catalyst (power density-530 mWcm-2; mass activity-123 mAmg-1Pt) compared to commercial Pt/C catalyst (power density-440 mWcm-2; mass activity-87 mAmg-1Pt), under identical conditions. The favourable conditions of synthesis of Pt-TiO2 catalyst achieved in acidic medium contribute to its enhanced properties.

Published
2018
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