Papers by Keyword: Transference Number

Abstract: The gel polymer electrolytes (GPEs) composed of polymethylmethacrylate (PMMA) with sodium trifluoromethanesulfonate (NaCF₃SO₃) salt dissolved in a binary mixture of ethylene carbonate (EC) and propylene carbonate (PC) organic solvents have been prepared by solution casting technique. The samples are prepared by varying the salt concentrations from 5 wt.% to 30 wt.%. Impedance spectroscopy measurement has been carried out to determine the ionic conductivity of the GPE samples. The sample containing 20 wt.% of NaCF₃SO₃ salt exhibits the highest room temperature ionic conductivity of 3.10 x 10^-3 S cm^-1. The conductivity of the GPEs has been found to depend on the salt concentration added to the sample though at higher salt concentration reveals decreasing in ionic conductivity due to ions association. The temperature dependence of conductivity from 303 K to 373 K is found to obey the Arrhenius rule. The ionic transference number, ti of GPEs has been estimated by DC polarization method and the value is found to be 0.95, 0.99, and 0.97 for the sample containing 5 wt.%, 20 wt.% and 30 wt.% respectively. This result is consistent with the conductivity studies.

Abstract: The gel polymer electrolytes (GPEs) composed of polymethylmethacrylate (PMMA) with lithium trifluoromethanesulfonate (LiCF₃SO₃) salt dissolved in a binary mixture of ethylene carbonate (EC) and propylene carbonate (PC) organic solvents have been prepared by the solution casting technique. The samples are prepared by varying the salt concentrations from 5 wt.% to 30 wt.%. Impedance spectroscopy measurement has been carried out to determine the ionic conductivity of the samples. The sample containing 25 wt.% of LiCF₃SO₃ salt exhibits the highest room temperature ionic conductivity of 2.56 x 10^-3 S cm^-1. The conductivity of the GPEs has been found to depend on the salt concentration added to the sample, while at higher salt concentration reveals a decrease in the ionic conductivity due to ions association. The temperature dependence of conductivity from 303 K to 373 K is found to obey the Arrhenius law. The ionic transference number, t_i of GPEs has been estimated by the DC polarization method and the value is found to be 0.98, 0.93, and 0.97 for the sample containing 25 wt.%, 5 wt.% and 30 wt.% respectively. This result is consistent with the conductivity studies.

Abstract: The electrolyte optimum composition consists of 1mol/L LiTFSI in the [EMIM]⁺[TFSI]^- mixed with EC and DMC in weight ratio of 60:20:20. The LiFePO₄/Li cell using 1 mol/L LiTFSI/([EMIM]⁺[TFSI]^-/EC/DMC) as electrolyte show that the first coulomb efficiency was 90% and the first discharge capacity was 168mAh g^-1. The 15th reversible capacities were maintain 157mAh g^-1 at 0.2C. Compared with traditional organic electrolyte and pure IL electrolyte, IL-based mixed electrolyte have good coulomb efficiencies and higher charge and discharge performances. The lithium transference number of IL-based mixed electrolyte at room temperature are 0.59. Thermal stability of IL-based mixed electrolyte higher than traditional organic electrolyte, and show almost non-flammability by the burning tests.

Abstract: The electrochemical methods of energy storage and conversion are of great interest for many practical applications. In the present investigations, PVA: MgSO4 based solid polymer electrolytes were prepared at different weight percent ratios using solution cast technique. FTIR spectroscopic studies were carried out to verify the complexation of the dopant with polymer. Force constant measurement was also carried out to ensure the interactions of polymer with salt. Optical absorption studies were carried out in the wave length range 200 to 600 nm. Absorption edge as well as bandgap values were evaluated. In order to ensure the ionic conduction of these electrolyte systems, transference number measurements were also carried out. The dominant conducting species were ions rather than electrons. These studies will help in verification or in investigating the feasibility of these electrolyte systems in polymer batteries, fuel cells, and other electrochemical systems.

Abstract: In this work, the polymethylmethacrylate (PMMA) based gel polymer electrolyte samples have been prepared by the solution casting technique. The composition range of the salt was from 3 wt% to 35 wt%. The ionic conductivity of the samples was measured using a.c. impedance technique. The highest room temperature conductivity was obtained from the sample containing 30 wt% of NaCF₃SO₃ salt, i.e. 5.31 x 10^-3 S cm^-1. The increase in the ionic conductivity with increasing salt concentrations is due to the increase in both concentration and mobility of charge carriers. The decrease in ionic conductivity at higher salt concentrations can be explained by aggregation of the ions, leading to the formation of ion-pair, thus decreasing the number of charge carriers and hence the ionic mobility. The conductivity-temperature dependence obeys the Arrhenius rule from which the activation energy was evaluated. The ionic transference number estimated by dc polarization method revealed that the conducting species are predominantly ions.

Abstract: Free standing polymer electrolyte films comprising of ammonium trifluoromethane sulfonate in poly(ethyl methacrylate) were prepared and characterized. The structural and electrical properties of the polymer electrolytes were investigated by X-ray diffraction and a.c. impedance spectroscopy, respectively. The formation of polymer-salt complex has been confirmed by Fourier transform infrared spectroscopy study. Conductivity of the polymer electrolytes increased with salt content. The highest ionic conductivity in the order of 10-5 S cm-1 at room temperature was achieved for the system with 35 wt% of ammonium salt. The temperature dependence of conductivity obeyed the Vogel-Tammam-Fulcher relation. The activation energy has been calculated from the VTF formalism. The ionic transference number of the mobile ions estimated by Wagner’s polarization method was close to unity for the highest conducting sample implying that the conductivity was contributed by ions which was expected to be protons.