Hypothesis: In recent years, gel polymer electrolytes (quasi-solid state electrolytes) have attracted great attention as a suitable substitute for liquid electrolytes. On the other hand, ionic liquids could dramatically enhance the ionic conductivity of electrolytes. In this work, gel polymer electrolytes based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)/poly(ethylene oxide) (PEO) blends (for application in dye-sensitized solar cells (DSSCs)) and imidazoliumbased ionic liquids were prepared. It is supposed that blending these two polymers could reduce the degree of crystallization and increase the porosity of the electrolyte blend to yield a higher electrolyte uptake and ionic conductivity. Methods: Polymer blend electrolytes were prepared in different blend ratios and in the presence of either one of the ionic liquids including BMII or BMIMBF4 through phase inversion method and their properties were investigated by differential scanning calorimetry (DSC), mercury porosimetry, electrolyte uptake, and morphology to optimize the blend ratio. Findings: It was found that the blend ratio of 60/40 (w/w) PVDF-HFP/PEO has the highest porosity and electrolyte uptake. Crystallization investigations by DSC showed that there is a direct relationship between the decrease of crystallinity of two polymers and the increment of electrolyte ionic conductivity. Electrolyte uptake gradually increased with increasing PEO component concentration up to 40 wt%, and reached a maximum of 98. 49% and 89. 48% for BMIMBF4 and BMII, respectively. Beyond this concentration, a decrease in electrolyte uptake was seen, which is an undesirable feature for the produced samples. In this blend ratio ionic conductivity was measured as 2. 07 mS/cm and 1. 78 mS/cm for PVDF-HFP/PEO/BMIMBF4 and PVDF-HFP/ PEO/BMII electrolytes, respectively.

Today, the economic growth of countries depends on the supply of energy resources. In most countries, these resources include coal, oil, natural gas, and nuclear energy. However, the use of these resources faces various challenges, including the depletion of fossil fuel resources, environmental pollution and an escalating price. In order to reduce global reliance on finite natural resources and environmentally destructive fuels, many efforts have been made to replace them with renewable resources, such as solar energy, water, wind, and etc. Batteries are one of the most potential technologies for this purpose. Lithium batteries have become increasingly important energy storage systems in our daily lives, which play a significant role in electronics and electric vehicles. However, their practical applications are plagued by the safety issues from liquid electrolytes, especially when the batteries are exposed to mechanical, thermal, or electrical abuse conditions. Polymer electrolytes are being proposed as an alternative liquid electrolyte for building safer lithium batteries. In this review article, polymer electrolytes are divided into two large categories of solid polymer electrolytes and gel polymer electrolytes. The characteristics and properties of solid polymer electrolytes and gel polymer electrolytes are presented at the first. Then, the recent progress of common polymers, namely, poly(ethylene oxide), poly(methyl methacrylate), polyacrylonitrile, poly(vinylidene difluoride) and poly(vinylidene fluoride-hexafluoropropylene) copolymer, biopolymers (cellulose, polyurethane, polycaprolactone), polycarbonate and polysiloxanes as polymer host of polymer electrolytes will be discussed. Finally, we will discuss remaining challenges and future perspectives of the polymer electrolytes for high-performance lithium batteries. We hope that this paper can provide useful information for the development of new polymer electrolytes with excellent properties for use in lithium batteries.

Background: Polymer gels are an emerging new class of dosimeters which are being applied to the challenges of modern radiotherapy modalities. Research on gel dosimetry involves several scientific domains, one of which is the imaging techniques with which dose data is extracted from the dosimeters. In the current work, we present our preliminary results of investigating capability of X-ray CT for extracting brachytherapy dose distributions from a normoxic gel dosimeter. Materials and Methods: A normoxic radiosensitive polymer gel was fabricated under normal atmospheric conditions and poured into three phantoms. Using Cs137 brachytherapy sources, the phantoms were irradiated with different dose distributions with a LDR Selectron remote after-loader. To improve SNR, 25 images were obtained of each slice for image averaging and an averaged background image of an un-irradiated gel phantom was then subtracted for artifact removal. To further improve the accuracy, a self-consistent normalized method was used for calibration of the dosimeters based on an assumption of a linear dose response between zero and maximum dose regions in the gel. Results: Although results reveal very similar CT-number gradients to that of brachytherapy dose distributions, but the method does not fulfill brachytherapy dosimetry requirements. This might be due to the high prescribed doses in this study which in turn results in a large change in the CT numbers. This change in the CT numbers of the images can not be considered to have a linear relationship with dose which was the basic assumption of our calibration method, so the results are just qualitatively comparable. Conclusion: In this study, the results of using X-ray CT for brachytherapy polymer gel dosimetry is promising but not still satisfying. Improving a proper calibration method for correlating CT numbers to dose will be significantly helpful for performing measurements with CT. The main limitation for CT is still a low signal to noise ratio especially in lower dose areas.    

In this work, solid polymer electrolytes based on poly (e-caprolactone) (PCL) with lithium bis (oxalato) borate as a doping salt were prepared by solution cast technique using DMF as a solvent. The electrical DC conductivity and dielectric constant of the solid polymer electrolyte samples were investigated by electrochemical impedance spectroscopy over a frequency range from 50 Hz to 1 MHz. It was found that the DC conductivity increased with increase in the salt concentration to up to 4 wt% and thereafter decreased. Dielectric constant versus salt concentration was used to interpret the decrease in DC conductivity with increase in salt concentration. The DC conductivity as a function of temperature follows Arrhenius behavior in low temperature region, which reveals that ion conduction occurs through successful hopping. The curvature of DC conductivity at high temperatures indicates the contribution of segmental motion to ion conduction. High values for dielectric constant and dielectric loss were observed at low frequencies. The plateau of dielectric constant and dielectric loss at high frequencies can be observed as a result of rapid oscillation of the AC electric field. The HN dielectric function was utilized to study the dielectric relaxation. The experimental and theoretical data of dielectric constant are very close to each other at low temperatures. At high temperatures, the simulated data are more deviated from the experimental curve of dielectric constant due to the dominance of electrode polarization. The non-unity of relaxation parameters (a and b) reveals that the relaxation processes in PCL-based solid electrolyte is a non-Debye type of relaxation.