A.K. Arof

Ionic conductivity studies of plasticized poly(vinyl chloride) polymer electrolytes

Abstract The ionic conductivity studies have been conducted for poly (vinyl chloride) polymer electrolytes (PVC:LiCF 3 SO 3 :LiBF 4 :PC:EC) over a wide frequency regime. It was found that the addition of plasticizers significantly improved the ionic conductivity. The dielectric data were analyzed using complex impedance Z *, complex admittance A *, complex permittivity e * and complex electric modulus M * of the sample with the highest ionic conductivity at various temperatures. The conductivity–temperature data obeys the classical Arrhenius relationship.

FTIR studies of chitosan acetate based polymer electrolytes

Chitosan is the product when partially deacetylated chitin dissolves in dilute acetic acid. As such, depending on the degree of deacetylation, the carbonyl, C=O-NHR band can be observed at similar to1670 cm(-1) and the amine, NH2 band at 1590 cm(-1). When lithium triflate is added to chitosan to form a film of chitosan acetate-salt complex, the bands assigned to chitosan in the complex and the spectrum as a whole shift to lower wavenumbers. The carbonyl. band is observed to shift to as low as 1645 cm and the amine band to as low as 1560 cm(-1). These indicate chitosan-salt interactions. Also present are the bands due to lithium triflate i.e. similar to761, 1033, 1182 and 1263 cm(-1). When chitosan and ethylene carbonate (EC) are dissolved in acetic acid to form a film of plasticized chitosan acetate, the bands in the infrared spectrum of the films do not show any significant shift indicating that EC does not interact with chitosan. EC-LiCF3SO3 interactions are indicated by the shifting of the C=O bending band from 718 cm(-1) in the spectrum of EC to 725 cm(-1) in the EC-salt spectrum. The Li+-EC is also evident in the ring breathing region at 893 cm(-1) in the pure EC spectrum. This band has shifted to 898 cm(-1) in the EC-salt spectrum. C=O stretching in the doublet observed at 1774 and 1803 cm(-1) in the spectrum of pure EC has shifted to 1777 and 1808 cm(-1) in the EC-salt spectrum

Dielectric behaviour of PVC-based polymer electrolytes

Abstract Thin films of poly(vinyl chloride) (PVC)–poly(methyl methacrylate) (PMMA) blend with lithium triflate (LiCF 3 SO 3 ) salt and dibutyl phthalate (DBP) as plasticizer were prepared by solution casting method. The conductivity and dielectric measurements were carried out on these films as a function of frequency at various temperatures. The addition of DBP significantly improved the ionic conductivity. The conductivity–temperature plots were found to follow an Arrhenius nature. The dielectric behaviour was analysed using dielectric permittivity ( e ′), dissipation factor (tan δ ) and electric modulus ( M ′) of the samples.

Transparent conducting lithium-doped nickel oxide thin films by spray pyrolysis technique

Nickel oxide (NiO) and lithium-doped nickel oxide films were deposited by the spray pyrolysis technique using NiCl2 and LiCl as starting materials. All the films were greenish-grey in colour and confirmed by X-ray analysis. The best NiO films were obtained when the substrate temperature, Ts=480 °C where a conductivity of 2.1×10-1Ω-1 cm-1 and transparency above 80% in the visible region are achieved. High transparency (above 80%) and highly conducting NiO films were obtained when doped with lithium.

Conductivity enhancement due to ion dissociation in plasticized chitosan based polymer electrolytes

Abstract Cast films of chitosan acetate, plasticized chitosan acetate, chitosan acetate containing salt and plasticized chitosan acetate–salt complexes were used to obtain some insight on the mechanism of ionic conductivity in chitosan-based polymer electrolytes. The films are largely amorphous. The conductivity is due to the mobile ions from the salt. The role of the plasticizer is to dissociate the salt thereby increasing the number of mobile ions, which lead to conductivity enhancement. The conductivity was calculated using the bulk impedance obtained through impedance spectroscopy. The Cole–Cole plots illustrating the variation of the negative imaginary impedance with the real impedance do not always show the double layer reactance but the plot of dielectric constant ϵ r versus frequency tends to a maximum at low frequencies. The real and imaginary parts of the electrical modulus of samples containing salt show a “long tail” feature, which is not found in the electrical modulus spectra of the unsalted samples. This long tail feature can be attributed to high capacitance, which further supports the plasticizers role as an agent to dissociate the salt into ions.

Ionic conductivity studies of poly(vinyl alcohol) alkaline solid polymer electrolyte and its use in nickel–zinc cells

Abstract X-ray diffraction (XRD) pattern reveals that potassium hydroxide (KOH) disrupts the crystalline nature of poly(vinyl alcohol) (PVA)-based polymer electrolytes and converts them into an amorphous phase. The PVA–KOH alkaline solid polymer electrolyte (ASPE) system with PVA/KOH wt.% ratio of 60:40 exhibits the highest room temperature ionic conductivity of 8.5×10−4 S cm−1. This electrolyte was used in the fabrication of a nickel–zinc (Ni–Zn) cell. The cell was charged at a constant current of 10 mA for 1 h providing it with 1.6 V. The cell was cycled 100 times. At the end of the last cycle, the cell still contained a capacity of 5.5 mA h.

Structural, thermal and electrochemical cell characteristics of poly(vinyl chloride)-based polymer electrolytes

Abstract A study is made of a polymer electrolyte system composed of poly(vinyl chloride) (PVC) as a host polymer, lithium tetrafluoroborate (LiBF 4 ) and lithium triflate (LiCF 3 SO 3 ) as salts and a mixture of ethylene carbonate and propylene carbonate as plasticizers. X-ray diffraction (XRD) reveales that the salts and plasticizers disrupt the crystalline nature of PVC-based polymer electrolytes and converts them into an amorphous phase. Differential scanning calorimetry studies suggest that the plasticized samples have lower values of the glass tranisition temperature T g , and thermogravimetric studies show that the thermal stability of the polymer electrolytes decreases with addition of plasticizers. The plasticized PVC electrolyte is used in the fabrication of electrochemical cells. The open-circuit voltage, discharge time for the plateau region, etc. are evaluated.

FTIR Studies of plasticized poly(vinyl alcohol)-chitosan blend doped With NH4NO3 polymer electrolyte membrane

Fourier transform infrared (FTIR) spectroscopy studies of poly(vinyl alcohol) (PVA), and chitosan polymer blend doped with ammonium nitrate (NH(4)NO(3)) salt and plasticized with ethylene carbonate (EC) have been performed with emphasis on the shift of the carboxamide, amine and hydroxyl bands. 1% acetic acid solution was used as the solvent. It is observed from the chitosan film spectrum that evidence of polymer-solvent interaction can be observed from the shifting of the carboxamide band at 1660 cm(-1) and the amine band at 1591 cm(-1) to 1650 and 1557 cm(-1) respectively and the shift of the hydroxyl band from 3377 to 3354 cm(-1). The hydroxyl band in the spectrum of PVA powder is observed at 3354 cm(-1) and is observed at 3343 cm(-1) in the spectrum of the PVA film. On addition of NH(4)NO(3) up to 30 wt.%, the carboxamide, amine and hydroxyl bands shifted from 1650, 1557 and 3354 cm(-1) to 1642, 1541 and 3348 cm(-1) indicating that the chitosan has complexed with the salt. In the PVA-NH(4)NO(3) spectrum, the hydroxyl band has shifted from 3343 to 3272 cm(-1) on addition of salt from 10 to 30 wt.%. EC acts as a plasticizing agent since there is no shift in the bands as observed in the spectrum of PVA-chitosan-EC films. The mechanism of ion migration is proposed for the plasticized and unplasticized PVA-chitosan-NH(4)NO(3) systems. In the spectrum of PVA-chitosan-NH(4)NO(3)-EC complex, the doublet CO stretching in EC is observed in the vicinity 1800 and 1700. This indicates that there is some interaction between the salt and EC.

FTIR studies of DMF plasticized polyvinyledene fluoride based polymer electrolytes

FTIR studies of the polymer polyvinyledene fluoride (PVDF), plasticizer dimethyl formamide (DMF) and their mixtures with lithium tetrafluoroborate (LiBF4) were carried out. LiBF4–DMF spectra for various salt concentrations showed shifting of the band at 659 cm−1 to higher wavenumber at 680 cm−1. The band at 659 cm−1 represents the OCN group of DMF. The interaction is between the Li cation and the oxygen atom of the OCN since the IR spectrum did not show any shift in the CN symmetric stretching band due to LiN interaction. The splitting of the CN symmetric stretching vibration of the plasticizer into a doublet at 860 and 880 cm−1 is evidence of plasticizer–polymer interaction. With increasing PVDF content the intensity of the bands at 1257, 1093 and 1063 cm−1, assigned to CN asymmetric and CH3 rocking (out of phase/in phase) vibrational modes of DMF, changes and shifts to lower wavenumbers. PVDF and LiBF4 interaction is weak and is shown by the broadening and shifting of the bands corresponding to PVDF.

Dielectric behaviour and AC conductivity of LiCF3SO3 doped H-chitosan polymer films

H-chitosan that exhibited solubility in THF was prepared by acyl modification of chitosan. Films of H-chitosan containing LiCF3SO3 were prepared by the solution cast technique. The effect of salt concentration on the frequency-dependent dielectric properties of H-chitosan: LiCF3SO3 complexes were investigated by impedance spectroscopy, in the temperature range from 243 to 373 K. The dielectric properties and ac conductivity of the samples prepared have been analyzed. The dielectric constant increases sharply with temperature in the low frequency region. At higher frequencies, the effect of temperature on the dielectric constant is negligible. The values of dielectric constant were also found to increase with increasing conductivity of the samples. The imaginary part, Mi of electrical modulus shows the formation of dispersion peak. Relaxation times for the ionic charge carriers were extracted from the loss tangent maximum peak at various temperatures. The plot of relaxation times as a function of temperature shows Arrhenius type behaviour. The ac conductivity was found to obey the universal power law and as the temperature increases, the feature of σ(θ) α θn is more predominant. The temperature dependence of the power law exponent n is reasonably interpreted by the overlapping large polaron tunneling (OLPT) model.