N. S. Mohamed

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.

Polymer batteries fabricated from lithium complexed acetylated chitosan

Abstract It is found that 0.8 g lithium nitrate added to a solution of 1 g chitosan dissolved in 100 ml 1% acetic acid produces a film, via the solution cast technique, with a maximum electrical conductivity of the order of 10−4 S cm−1. This film is amorphous. For battery fabrication, metal powder and hydrogen storage material are used for the anode, and a metallic oxide (MnO2) for the cathode material. The anode contains a mixture of zinc and zinc sulfate in the ratio of 3:1. Batteries with configurations Zn + ZnSO4·7H2O/LiCAC/I2 + C and Zn + ZnSO4·7H2O/ LiCAC/MnO2+C (LiCAC = lithium complexed acetylated chitosan) provide open-circuit voltages of 1.113 and 0.765 V, respectively. The discharge characteristics of the batteries are presented. Unfortunately, only short lifetimes and small discharge currents can be obtained. This is possibly due to incompatibility between the electrode materials and the electrolytes.

Silver nitrate doped chitosan acetate films and electrochemical cell performance

Abstract Chitosan acetate-silver nitrate (AgNO3) complexes were prepared in thin film form by the solution cast technique. The electrical conductivity σ of the films was measured by impedance spectroscopy. The plot of σ vs. dopant content indicates that σ increases with increasing dopant content up to a dopant amount of 0.25 g where σ reaches a maximum. The plot of In σT vs. 103/T (278 K ⩽ T ⩽ 313 K) for each film sample seems to obey the Arrhenius rule. Here σ is the electrical conductivity and T is temperature in Kelvin. From these plots the activation energy, EA was obtained and the graph of activation energy versus dopant content was plotted. From these plots the increase in σ can be explained in terms of the decrease in EA. The shape of the Cole-Cole plots seem to imply that the transport mechanism of Ag+ ions occurs by way of diffusion. The film with the highest ionic conductivity of 2.6 × 10−5 S cm−1 was used to fabricate Ag/AgNO3 — chitosan/I2 electrochemical cells. The average open circuit voltage of these cells is 0.672 V justifying the material to be an Ag+ ion conductor. By the electromotive force method, the ionic transference number of the film is 0.98 implying the low electronic conductivity of the material and its suitability as an electrolyte for electrochemical cell fabrication. Characteristics of such cells are presented and discussed.

Studies of alkaline solid polymer electrolyte and mechanically alloyed polycrystalline Mg2Ni for use in nickel metal hydride batteries

Ni–MH cells comprising PVA-KOH solid polymer electrolyte and mechanically alloyed Mg2Ni as the negative electrode have been fabricated. The alkaline solid polymer electrolyte with PVA:KOH wt.% ratio of 60:40 exhibits the highest room temperature ionic conductivity of 8.5×10−4 S cm−1. This sample is mostly amorphous. The cell was charged at a constant current of 10 mA and discharged at 0.1 mA. The discharge characteristics improved upon cycling and the plateau voltage maintained above 1.2 V for ∼10 h.

Properties of PEMA-NH4CF3SO3 added to BMATSFI ionic liquid

Polymer electrolyte films, comprising ammonium trifluoromethanesulfonate salt and butyl-trimethyl ammonium bis(trifluoromethylsulfonyl)imide ionic liquid immobilized in poly (ethyl methacrylate) was studied. Structural, morphological, thermal and electrical properties of the polymer electrolyte films were investigated by differential scanning calorimetry, scanning electron microscopy, and impedance spectroscopy, respectively. Interactions of the salt and ionic liquid with the host polymer were investigated by Fourier transform infra-red spectroscopy. Electrochemical stability of the electrolytes was determined using linear sweep voltammetry and transference numbers corresponding to ionic transport has been evaluated by means of the Wagner polarization technique. The highest conductivity achieved is in the order of 10−4 S cm−1 for the film added with 35 wt % butyl trimethylammonium bis (trifluoromethanesulfonyl)imide. The film has high amorphicity and low glass transition temperature of 2 °C. The film is electrochemically stable up to 1.8 V. The ion transference number in the polymer film is 0.82 and the conductivity behavior obeys Vogel-Tamman-Fulcher equation.

Investigation of the Ionic Conduction Mechanism in Carboxymethyl Cellulose/Chitosan Biopolymer Blend Electrolyte Impregnated with Ammonium Nitrate

In the present work, an attempt has been made to prepare a new natural biopolymer blend electrolyte of carboxymethyl cellulose/chitosan impregnated with NH4NO3 by the solution casting technique. The conductivity for the system was measured by impedance spectroscopy. The incorporation of 40 wt.% NH4NO3 optimized the ambient temperature conductivity of the electrolyte up to 1.03 × 10−5 S cm−1. All electrolytes were found to follow the Arrhenius relationship. Dielectric studies confirmed that the electrolytes obey non-Debye behavior. The temperature dependence of the power law exponent s for the highest conducting film can be represented by the correlated barrier hopping model.

Conductivity and Dielectric Behavior Studies of Carboxymethyl Cellulose from Kenaf Bast Fiber Incorporated with Ammonium Acetate-BMATFSI Biopolymer Electrolytes

This work was undertaken to study the conductivity and dielectric behavior of a biopolymer electrolyte based on carboxymethyl cellulose that was synthesized from kenaf fiber. Biopolymer electrolytes comprised of various weight percentage ratios of the host polymer, ammonium acetate salt, and butyl-trimethyl ammonium bis(trifluoromethylsulfonyl)imide ionic liquid were prepared by the solution casting technique. The conductivity values were determined by impedance spectroscopy. The highest conductivity found was 2.18 × 10−3 S cm−1 at ambient temperature for the film incorporated with 20 wt.% salt and 20 wt.% ionic liquid. In order to understand the conductivity behavior, a dielectric study was carried out. The results showed that the system obeys the Arrhenius rule and confirmed non-Debye behavior in the sample.

Simulation model of the fractal patterns in ionic conducting polymer films

Normally polymer electrolyte membranes are prepared and studied for applications in electrochemical devices. In this work, polymer electrolyte membranes have been used as the media to culture fractals. In order to simulate the growth patterns and stages of the fractals, a model has been identified based on the Brownian motion theory. A computer coding has been developed for the model to simulate and visualize the fractal growth. This computer program has been successful in simulating the growth of the fractal and in calculating the fractal dimension of each of the simulated fractal patterns. The fractal dimensions of the simulated fractals are comparable with the values obtained in the original fractals observed in the polymer electrolyte membrane. This indicates that the model developed in the present work is within acceptable conformity with the original fractal.

The Effect of Lithium Iodide to the Properties of Carboxymethyl κ-Carrageenan/Carboxymethyl Cellulose Polymer Electrolyte and Dye-Sensitized Solar Cell Performance

This study was undertaken to investigate the solid biopolymer electrolytes based on a carboxymethyl κ-carrageenan/carboxymethyl cellulose blend complexed with lithium iodide of various weight ratios. The complexation of the doping salt with the polymer blend was confirmed by Fourier transform infrared spectroscopy. Ionic conductivity of the film was determined by impedance spectroscopy in the frequency range of 10 Hz to 4 MHz and in the temperature range of 303–338 K. The ionic conductivity increased with the increase in lithium iodide concentration as well as temperature. The membrane comprising 30 wt % of lithium iodide was found to give the highest conductivity of 3.89 × 10−3 S·cm−1 at room temperature. The increase in conductivity was associated with the increase in the number as well as the mobility of the charge carries. The conductivity increase with temperature followed the Vogel–Tamman–Fulcher model. The fabricated dye-sensitive solar cell, FTO/TiO2-dye/CMKC/CMCE-LiI (30 wt %) +I2/Pt exhibited the highest conversion efficiency of 0.11% at a light intensity of 100 mW·cm−2. This indicated that the biopolymer blend electrolyte system has potential for use in dye-sensitized solar cells.

The influences of ionic liquid to the properties of poly(ethylmethacrylate) based electrolyte

A new and thermally stable poly (ethyl methacrylate) incorporated with 1-ethyl-3-methylimidazolium bis(trifluorosulfonyl) imide ionic liquid electrolytes were prepared using solution casting technique. Interaction between the polymer and ionic liquid was confirmed by Fourier transform infrared spectroscopy. The presence of amorphous phase which increased with increasing ionic liquid content was observed from scanning electron microscopic analysis. This result can be correlated to the decreased in glass transition temperature and the melting point of the sample obtained from differential scanning calorimetry. The addition of EMITFSI in PEMA matrix improved the thermal stability of the polymer electrolytes up to approximately 300 °C. The sample showed a maximum conductivity of 9.75 × 10−5 S cm−1 at 100 °C with activation energy value of 0.69 eV. The result obtained from linear sweep voltammetry revealed that the electrolyte system exhibited a reasonably wide electrochemical window.