N. H. Zainol

Studies on Sodium Ion Conducting Gel Polymer Electrolytes

Sodium ion conducting gel polymer electrolyte (GPE) films consisting of polyvinylidenefluoride-co-hexafluoropropylene (PVdF-HFP) as a polymer host were prepared using the solution casting technique. Sodium trifluoromethane-sulfonate (NaCF3SO3) was used as an ionic salt and the mixture of ethylene carbonate (EC) and propylene carbonate (PC) as the solvent plasticizer. The GPE films were found to be stable up to temperature of 145 °C as shown by TGA analysis. The AC impedance study show that the optimum conductivity of 2.50 x 10-3 S cm-1 at room temperature is achieved for the film containing 20 wt.% of NaCF3SO3 salt. The temperature dependence of conductivity obeys VTF relation in the temperature range of 303 K to 373 K.

Ionic transport and electrochemical stability of PVDF-HFP based gel polymer electrolytes

The gel polymer electrolytes (GPEs) samples consisting of polyvinylidenefluoride-co-hexafluoropropylene (PVDF-HFP), ethylene carbonate (EC) and propylene carbonate (PC) with different concentrations of magnesium triflate salt, Mg(CF3SO3)2 were prepared using the solution casting technique. The ionic conductivity of the GPEs was studied by using a.c impedance spectroscopy and the sample containing 20 wt% salt exhibited the highest conductivity of 5.11 × l0−3 Scm−1. Ionic transport number of the GPEs shows that the samples contain ionic species as main charge carrier while cationic transport number for the highest conducting sample was found to be 0.27. The electrochemical properties of the GPEs were studied using Linear Sweep Voltammetry (LSV) and Cyclic Voltammetry (CV). The GPEs show high electrochemical stability ∼3.5V (versus Mg2+/Mg) where the highest conducting sample exhibited the highest stability.

Ionic Conductivity, Morphology and Transference Number of Sodium Ion in PMMA Based Gel Polymer Electrolytes

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.

Transport and Morphological Properties of Gel Polymer Electrolytes Containing Mg(CF3SO3)2

Magnesium-ion conducting gel polymer electrolytes (GPEs) based on PMMA with ethylene carbonate (EC) and propylene carbonate (PC) as a plasticizing solvent were prepared via the solution casting technique. Mg(CF3SO3)2 salt was used as source of magnesium ions, Mg2+. The variation of conductivity with salt concentrations, from 5 wt.% to 30 wt.% was studied. The gel polymer electrolyte with composition 20 wt.% of Mg(CF3SO3)2 exhibited the highest conductivity of 1.27 x 10-3 S cm-1 at room temperature. The conductivity-temperature dependence of gel polymer electrolyte films obeys Arrhenius behaviour with activation energy in the range of 0.18 eV to 0.26 eV. Ionic transport number was evaluated using DC polarization technique and it reveals the conducting species are predominantly ions. It is found that the ionic conductivity and transport properties of the prepared GPEs are consistent with the X-Ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM) studies.

Synthesis of LiMn1.9Ti0.1O4 via a combustion method

Lithium Manganese Oxide, LiMn2O4 is being considered as one of the favourable options to replace the current cathode material, LiCoO2. LiMn2O4 have several advantages such as lower cost and non-toxic. In this research, Mn has been partially substituted with Ti in order to overcome the problem of severe capacity fading. LiMn1.9Ti0.1O4 was prepared by a self-propagating combustion method (SPC). Thermal analysis was carried out by Simultaneous Thermogravinometric Analyzer (STA). The material was annealed at 800 °C for 24 h and 48 h respectively. The Phase analysis was done by performing X-Ray Diffraction (XRD) and also to check the purity of the materials.

Phases of LiMn1.84V0.06Ti0.1O4 cathode material

In this work, LiMn1.84V0.06Ti0.1O4 was prepared via a combustion method using citric acid as a reductant. The precursor obtained was annealed at 700 °C for 24h in a furnace. The thermal profile of the precursor was obtained by simultaneous thermogravimetric analysis (STA). The observed material was characterized by X-ray Diffraction (XRD) and found to be pure and single-phase of cubic structure. The electrochemical performance of LiMn1.84V0.06Ti0.1O4 cathode material was studied by applying a constant current of 1.0 mA at a voltage range of 4.2 to 2.5 V. The specific capacity of LiMn1.84V0.06Ti0.1O4 cathode material at the 1st cycle shows the value of 95mAh/g which is less than the specific capacity of LiMn2O4, which is 117 mAh/g.

Study of cathode material, LiNi0.7Co0.3-(x+y)TixSnyO2 (x=0.1;y=0.01) prepared by combustion method

In this work, LiNi0.7Co0.3-(x+y)TixSnyO2 (x = 0.1; y = 0.01) was prepared via a combustion method using citric acid (CA) as a reductant. The precursor obtained were annealed at 650 °C, 750 °C and 850 °C for 24h in a furnace. The observed material was characterized by XRD as a pure and single-phase of rhombohedral crystal system with R-3m space group. FESEM images of LiNi0.7Co0.3 -(x+y)TixSn yO2 (x = 0.1; y = 0.01) material show homogeneous structure with polyhedral-type crystals. The charge-discharge profile of LiNi0.7Co0.3-(x+y)TixSn yO2 (x = 0.1; y = 0.01) material was studied by applying a constant current of 1.0 mA at a voltage range of 4.2 to 2.5 V. The specific capacity of annealed LiNi0.7Co0.3 -(x+y)TixSn yO2 (x = 0.1; y = 0.01) material at 850 °C shows highest value which is 70.05 mAh/g at the 1st cycle and it decreased to 30.86 mAh/g at the 30th cycle.