Mohamed Nor Sabirin

Ionic Conductivity of PVC-NH4I-EC Proton Conducting Polymer Electrolytes

Poly(vinyl) chloride (PVC)-NH4I-EC films have been prepared by solution cast technique. The sample containing 30 wt. % NH4I exhibited highest room temperature conductivity of 4.60 × 10-7 S cm-1. The conductivity increased to 1.08 × 10-6 Scm-1 when 15 wt. % of ethylene carbonate (EC) was added to 70 wt. % PVC - 30 wt. % NH4I. Fourier Transform Infrared (FTIR) showed evidence of polymer–salt complexation while DSC showed increase in glass transition temperature (Tg ) of PVC -NH4I - EC polymer electrolytes. The conductivity behavior of the studied system could be accounted by the changes in Tg values.

Characterization of PVDF-HFP-LiCF3SO3-ZrO2 Nanocomposite Polymer Electrolyte Systems

Nanocomposite polymer electrolytes were prepared by incorporating different amounts of zirconium oxide (ZrO2) nanofiller to poly(vinylidene fluoride-co-hexafluoropropylene)-lithium trifluoromethane sulfonate (PVDF-HFP-LiCF3SO3). X-ray diffraction (XRD) study has been carried out to investigate the structural features of the electrolyte films while a.c. impedance spectroscopy has been performed to investigate their electrical properties. The conductivity of nanocomposite polymer electrolyte systems is influenced by nanofiller concentration. The increase in conductivity is attributable to the increase in the fraction of amorphous region and the number of charge carriers and vice versa. The highest conductivity obtained is in the order of 10-3 S cm-1 for the system dispersed with 5 wt% of ZrO2 nanofiller.

Studies of Poly(Ethyl Methacrylate) Complexed with Ammonium Trifluoromethanesulfonate

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.

Ionic Conductivity of PVDF-HFP/MG49 Based Solid Polymer Electrolyte

Blend-based polymer electrolytes composed of PVDF-HFP/MG-49 (70/30) and LiClO4 as lithium salt has been studied. Solution casting method was applied to prepare the polymer electrolyte. Electrochemical impedance spectroscopy (EIS) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the electrolyte films. The maximum value of 2.51×10ˉ6 S cm-1 was obtained at ambient temperature for the 30 wt. % of LiClO4 and the conductivity increased to 1.10×10ˉ3 S cm-1 by increasing the temperature up to 383 K. FTIR spectra demonstrated that complexation occurred between the polymers and lithium salt.

Li2CO3 – Al2O3 Composite Solid Electrolytes Prepared by Sol Gel Method

Composite solid electrolytes in the system (1-x)Li2CO3-xAl2O3, where x = 0.1–0.7 were prepared by sol gel method using lithium carbonate and aluminum oxide precursors in ethanol. The gels obtained due to the addition of citric acid were calcined at 80 and 100 oC. Their structural, thermodynamic and electrical properties were investigated by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and impedance spectroscopy. The results indicated that interface phases of crystalline and amorphous exist in this composite system of (1-x)Li2CO3-xAl2O3. The presence of the interface phases are due to the chemical and physical interactions between both crystalline Li2CO3 and Al2O3. The Arrhenius plot of the composite system showed non-linear curves and reached maximum values of ∼10−4 - 10−5 S cm-1 at 150 -180 °C. Based on the results of this study, it can be concluded that the sol gel method used in the preparation of the composite system, has an important role to crystal morphology changes that results in high ionic conductivity.

Characterization of (ENR-50)-Ionic Liquid Based Electrolyte System

Ionic liquid based on imidazolium cation; 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMITFSI) has been incorporated with epoxidized natural rubber-50 (ENR-50) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to obtain electrolyte material. Fourier transform infrared spectroscopy (FTIR) spectra showed evidence of complexation between ENR-50, EMITFSI and LiTFSI. Glass transition temperature, Tg displayed an increasing trend with increase in salt concentration. The incorporation of EMITFSI resulted in an increase in ionic conductivity. The increase in ionic conductivity was attributed to the role of ionic liquid which reduced Tg, thus, facilitated ion conduction in the system. The highest ionic conductivity at room temperature was 5.72 ´ 10-4 S cm-1 for sample containing 20 wt% of EMITFSI and 50 wt% of LiTFSI.

LiCF3SO3 – CeO2 Composite Electrolytes Prepared by Sol-Gel Technique: Structural and Conductivity Studies

(100-x) LiCF3SO3 + (x) CeO2 composite electrolytes were prepared using sol-gel technique followed by sintering at 300 °C for four hours. Structural property and conductivity of the prepared composite electrolytes were studied using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDX) analysis and Impedance Spectroscopy. The XRD spectra show only crystalline peaks of CeO2 indicating that LiCF3SO3 exists in the form of amorphous phase. This is confirmed by SEM and EDX analyses. The highest ionic conductivity at room temperature is found to be in the order of 10-3 S cm-1 for the composite of 70 mol % LiCF3SO3 - 30 mol % CeO2. The conductivity of the composite electrolytes is observed to increase gradually with temperature.

Studies of ENR-50 and LiN(SO2CF3)2 Electrolyte System

In this work, electrolyte films based on epoxidized natural rubber-50 (ENR-50) and lithium imide (LiN(SO2CF3)2) salt were prepared using solution casting method. X-ray diffraction pattern for undoped ENR-50 shows a broad peak which indicated amorphous nature of the film. The intensity of ENR-50 peak decreases with increase in salt concentration. Thermal property study was carried out using Differential Scanning Calorimetry (DSC) to determine glass transition temperature, Tg. The DSC result displays an increasing trend of Tg with increase in salt concentration and opposite to the trend of variation of conductivity with salt concentration. This indicates that the increase in Tg dose not give adverse effect on ionic conductivity. The increase in Tg with concentration of salt may be due to formation of transient cross-linking between ENR-50 chains via the coordinated interaction between ENR-50 chains and LiN(SO2CF3)2. The highest room temperature ionic conductivity obtained is in the order of 10-5 S cm-1 for the film containing 50 wt.% of LiN(SO2CF3)2. The ionic conductivity of this electrolyte system increases with increase in temperature and obeys the Vogel-Tammam-Fulcher (VTF) relation in the temperature range of 303–373 K. The increase in ionic conductivity of the electrolyte system could be correlated to increase in number of charge carriers and the migration rate of charge carriers.

Characterization of LiClO4-SiO2 Composite Electrolyte Prepared by Modified Sol-Gel Method

(100-x) LiClO4-xSiO2 (x is mol %) solid composite electrolytes in various compositions were synthesized by modified sol-gel process with sintering at 200 °C. The electrical and structural properties of the composites were investigated. The ionic conductivity of the composites increased with mol % of the dispersoid and then decreased. The highest conductivity was obtained for x = 50 mol % with a value of 4.06 × 10-7 S cm-1 at room temperature. The enhancement in conductivity was more than two orders of magnitude when compared to the host material. The higher conductivity in the SiO2 dispersed system was interpreted in terms of space charge layer and percolation theory. The temperature dependence of conductivity of all samples were Arrhenian in nature and exhibited a maximum of 10-3 S cm-1 at T = 140 °C for x = 50 mol %. XRD spectra showed presence of heterogeneous phase of LiClO4-SiO2 crystalline peaks.

Synthesis, Characterization and Charge-Discharge Profile of LiMn0.3Co0.3Ni0.3Fe0.1O2 Prepared via Sol-Gel Method

LiCoO2 is a well established commercial Li-ion battery cathode. However, due to cost constraints and the toxicity of the metal, other layered compounds should be investigated. In this paper, layered LiMn0.3Co0.3Ni0.3Fe0.1O2 were prepared using sol-gel method with CH3COOLi•2H2O, (CH3CO2)2Mn•4H2O, (CH3CO2)2Co•4H2O, (CH3CO2)2Ni•4H2O and Fe (NO3)3•9H2O as starting materials. The sample was characterized by simultaneous thermogravimetric analysis, x-ray powder diffraction and scanning electron microscopy. The electrochemical characteristics were studied by a charge-discharge cycle done on the fabricated cell using a charge current of 1.0 mA and a discharge current 0.5 mA between 4.2 and 0.5 V. The XRD results showed that the layered LiMn0.3Co0.3Ni0.3Fe0.1O2 were of pure phase with discharge capacity of about 136 mAhg-1. The batteries were then subjected to a series of charge-discharge cycling in the voltage range of 2.5 to 4.2 V. The results showed there was little loss of capacity after 10 cycles.