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A.K. Arof
Physics Department, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia
Astronomy Computer Science & IT Earth & Planetary Sciences Electrical & Electronics Engineering Energy Engineering

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Two percolations model for conductivity-salt concentration in PVC-LiPF6 system R.H.Y. Subban; M.Z.A. Yahya; R. Puteh; A.K. Arof
Indonesian Journal of Physics Vol 15 No 3 (2004): Vol. 15 No. 3, July 2004
Publisher : Institut Teknologi Bandung

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Abstract

Lithium hexafluorophosphate (LiPF6) doped polyvinyl chloride (PVC) polymer electrolytes were prepared by the solution cast technique. LiPF6 has been claimed as the best salt for use in electrolytes for lithium ion batteries. In this work, 1.0 g of PVC and 1.0 g of LiPF6 were dissolved in tetrahydrofuran (THF). The LiPF6 was then substituted with LiCF3SO3 in different weight percentages. The solutions were cast in different petri dishes and left to form films at room temperature. The films were kept in a dessicator for a period of one week to ensure complete dryness. Impedance spectroscopy was used to obtain the bulk resistance from which the conductivity was calculated. The conductivity-salt concentration graph showed two peaks at 0.2g LiCF3SO3 and 0.8 g LiCF3SO3. In glasses, the conductivity is due to the conduction of cations, but in polymers both anions and cations are conducting. In some cases, the transference number of anions is greater than that of the cations. In most cases, the conductivity-salt concentration graph shows only one peak. In such observation, increase in conductivity is explained by the increase in number of free mobile ions and the decrease in conductivity is attributable to ion reassociation. The results in this work cannot be satisfactorily explained by the above mechanism. The two salient peaks observed maybe plausibly explained by the two percolations model in which both positive and negative ions contribute to the conductivity. The first peak is attributed to the lithium ions and the second peak is attributed to the PF6- and CF3SO3- ions. This is also in accordance to the results from transient ionic current experiments, which indicate that the cations have a higher mobility than anions.
Investigation on PVDF Based Solid Polymer Electrolytes for Rechargeable Lithium Batteries N.S. Mohamed; S.A. Hashim Ali; A.K. Arof
Indonesian Journal of Physics Vol 15 No 3 (2004): Vol. 15 No. 3, July 2004
Publisher : Institut Teknologi Bandung

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Solid polymer electrolytes consisting of PVDF and LiCF3SO3 plasticized with different amounts of EC plasticizer were prepared by solution casting method. The addition of plasticizer significantly improved the ionic conductivity. The temperature dependence of ionic conductivity of the plasticized PVDF film follows VTF empirical form, i.e the migration of ions depends mainly on the segmental movements of the polymer chain in the amorphous region. The characteristics of the cell employing the highest conducting system are also presented in this paper.
Stretching hydrolysis in LiI-Li2WO4-Li3PO4 by infrared spectroscopy A.H. Ahmad; M.Z.A. Yahya; R. Puteh; A.K. Arof
Indonesian Journal of Physics Vol 15 No 3 (2004): Vol. 15 No. 3, July 2004
Publisher : Institut Teknologi Bandung

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Infrared spectroscopy is a useful tool to probe the formation of polyhedral structures in alkali halide-oxysalts. LiI-Li2WO4- Li3PO4 is an example of alkali halide-oxysalt. These materials have been proposed as superionic materials for use as electrolytes in electrochemical devices. One of the pertinent problems in lithiated superionic materials is their hygroscopic property that can seriously affect the conductivity of the materials. In the present work, LiI-Li2WO4- Li3PO4 has been prepared by the sintering method in order to ensure removal of water from the samples. Fourier Transform Infrared (FTIR) spectra show that the band at 1634 cm-1 due to lithium tungstate, the band at 1628 cm-1 due to lithium iodide has overlapped to form a single band at around 1640 cm-1. The two bands at 1050 and 590 cm-1are assigned to pure lithium phosphate. The FTIR spectrum of the ternary system is almost similar to that of the binary system and they are quite similar to the spectrum of lithium tungstate. FTIR shows there is a strong broad band centered at 3400 cm-1 in the binary sample but the band decreases in width on addition of Li3PO4. This band is an indication of stretching hydrolysis. A medium band is also observed at 1505 cm-1, which is due to H-O-H bending motion This band almost disappears as the amount of Li3PO4 is increased to 30 wt.%. These results indicate that with further treatment the sample LiI-Li2WO4- Li3PO4 has potential for use in lithium batteries.
Transport and AC Impedance Studies of Plasticized-Chitosan Based Polymer Electrolytes A.S.A Khiar; A.K. Arof
Indonesian Journal of Physics Vol 22 No 4 (2011): Vol. 22 No. 4, October 2011
Publisher : Institut Teknologi Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (165.477 KB) | DOI: 10.5614/itb.ijp.2011.22.4.6

Abstract

Dimethyl Carbonate (DMC)-plasticized chitosan-based polymer electrolytes were prepared in the present work. The sample 37.5 wt% chitosan - 37.5 wt% NH4CF3SO3 - 25 wt% DMC showed the highest conductivity of (1.95±0.15) x 10-6 S/cm. From calculated values obtained using the Rice and Roth model, the increase in conductivity is due to the increase in the number density of mobile ions. Universal Power Law was used to analyze the AC conductivity of the sample. Arrhenius behavior was observed in the plot of hopping frequency; ωP against temperature. The AC conductivity master curve was obtained for the highest conducting sample when scaled vertically by σ and horizontally by ω .
Co-Authors A.H. Ahmad A.S.A Khiar M.Z.A. Yahya M.Z.A. Yahya N.S. Mohamed R. Puteh R.H.Y. Subban S.A. Hashim Ali