Bacto agar-based gel polymer electrolyte

The biopolymer of a Bacto agar-based gel polymer electrolyte (GPE) was prepared by addition of NaI and I₂ as redox couple. The prepared GPE was characterized using impedance spectroscopy and X-ray diffraction (XRD) in order to determine its electrical and structural properties, respectively. An optimized ionic conductivity of 12.41 × 10⁻⁴ S cm⁻¹ was achieved for the samples containing 1.6 M NaI and 50 μL I₂. Meanwhile, XRD revealed that the addition of NaI and I₂ altered agar properties and formed an amorphous structure. Linear sweep voltammetry showed that the electrochemical stability window of the sample had a working voltage of 2.0 V.     

Electrical and structural studies of a LiBOB-based gel polymer electrolyte

A series of gel polymer electrolytes (GPEs) containing lithium bis(oxalato)borate (LiBOB), propylene carbonate (PC), and ethylene carbonate (EC) have been investigated. Poly(ethylene oxide) (PEO) was used as the polymer. First, a series of liquid electrolytes was prepared by varying the Li:O ratio and obtained the best composition giving the highest conductivity of 7.1?×?10^?3 S cm^?1 at room temperature. Then, the PEO-based GPEs were prepared by adding different amounts of LiBOB and PEO into a mixture of equal weights of EC and PC (40 % of each from the total weight). The gel electrolyte comprises of 12.5 % of LiBOB, 7.5 % of PEO, 40 % of EC, and 40 % of PC gave the highest ionic conductivity of 5.8?×?10^?3 S cm^?1 at room temperature. From the DC polarization measurements, ionic nature of the gel electrolyte was confirmed. Fourier transform infrared (FTIR) spectra of electrolytes showed the Li⁺ ion coordination with EC and PC molecules. These interactions were exhibited in the peaks corresponding to ring breathing of EC at 893 cm^?1 and ring bending of EC and symmetric ring deformation of PC at 712 and 716 cm^?1 respectively. The presence of free Li⁺ ions and ion aggregates is evident in the peaks due to the symmetric stretching of O–B–O at 985 cm^?1.     

Effect of polar aprotic solvents on hydroxyethyl cellulose-based gel polymer electrolyte

Quasi-solid bioelectrolytes based on hydroxyethyl cellulose (HEC) and sodium iodide (NaI) in three different polar aprotic solvent systems, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and dimethylacetamide (DMA), were fabricated and characterized. FTIR studies revealed active solvent-ion interactions in DMF-based electrolytes in comparison to DMA and DMSO. The effect of the solvent system on the crystallinity of HEC gel electrolytes was more significant at low NaI concentration. In each solvent system, the highest ionic conductivity was achieved at 70 wt% NaI and generally DMF-based electrolytes showed higher conductivity than the other solvents. The availability of multiple complexation sites present in DMF is ascribed to improvement in ion mobility and hence conductivity. Rheological analysis was carried out to elucidate the mechanical properties of the gels. Generally, the mechanical strength of the polymer gels was unaffected by the type of solvent.     

Conductivity of nano-MIM diodes with a carbonaceous active medium in a model including percolation effects

A model proposed previously for processes in nano-MIM (metal-insulator-metal) diodes with a carbonaceous active medium is developed and refined. The inclusion of percolation effects in the insulating gap yields qualitatively new results and provides better agreement between the calculations and experimental data for physically reasonable values of all the parameters. An analysis of the model has made it possible to distinguish two different elements in the mechanism upon which it is based, which are important for understanding the essence of the processes that take place in electroformed nano-MIM diodes with a carbonaceous active medium: an internal negative feedback in the structure and modulation of the parameters of the cathode potential barrier. These elements show up in different ways in the observed characteristics of MIM structures. Zh. Tekh. Fiz. 69, 66–73 (November 1999)     

Electrical studies on ionic liquid-based gel polymer electrolyte for its application in EDLCs

Ionic liquid-based gel polymer electrolyte (GPE) has been synthesized using standard solution cast technique. Different weight percent of ionic liquid, 1-Butyl-3-methylimidazolium chloride (BMIMCl) and liquid electrolyte, ethylene carbonate (EC)–propylene carbonate (PC)–tetra ethyl ammonium tetra fluoro borate (TEABF₄) was incorporated in polymer, poly(vinylidene fluoride-co-hexafluoro propylene (PVdF-HFP) to obtain mechanically stable gel polymer electrolyte film (GPE) having maximum conductivity of ~10⁻³ S cm⁻¹ at room temperature, which is acceptable from device fabrication point of view. Potential window and ionic transference number has been obtained to examine the potential limit and ionic characteristics of optimized GPE system. Temperature dependence behavior of electrical conductivity curve follows Arrhenius nature in the temperature range of 303–373 K. Pattern of dielectric constant and its loss as a function of frequency and temperature have been studied and is being explained on the basis of electrode interfacial polarization effect. Frequency-dependent conductivity spectra obey the Jonscher’s power law. Further, optimized composition of GPE has been tested successfully for its application in supercapacitor fabrication with activated charcoal as an electrode material. Maximum specific capacitance of 118.6 mF cm⁻² equivalent to single electrode specific capacitance of 61.7 F g⁻¹ have been observed for the optimized GPE film.

     

Acrylamide based proton conducting polymer gel electrolyte for electric double layer capacitors

A new class of polymer gel electrolyte (PGE) was synthesized using acrylamide as host polymer and LiClO₄ as dopant. The polymer gel was subjected to electrochemical AC impedance analysis and thermal analysis. The polymer has conductivity in the order of 10⁻³ S cm⁻¹ at ambient temperature. Thermogravimetric analysis (TGA) revealed the effect of dopant on host polymer matrix. A supercapacitor was fabricated using acrylamide based polymer gel electrolyte with activated carbon as electrode material and it was subjected to various electrochemical techniques like cyclic voltammetry, electrochemical AC impedance analysis and galvanostatic charge–discharge tests at various current densities. From cyclic voltammetry a specific capacitance of 28 F/g was obtained at a scan rate of 10 mV/s. The capacitor had good self-discharge behavior and good cycle life of more than 10,000 cycles. The coulombic efficiency was more than 95%. These results indicate that this acrylamide-based polymer gel electrolyte doped with LiClO₄ is a potential electrolyte for electric double-layer capacitors (EDLCs).     

Electrical characterization of polymer composite gel under biasing as polar medium

Polyvinyl alcohol (PVA) composed with polymethyl methacrylate (PMMA) polymer hydrogel was prepared by using boric acid as a cross-linking agent. The semicrystalline phase of composite gel was detected by X-ray diffraction tool. The occupied polymer PMMA morphology exhibits cross-linked alignment shown by scanning electron microscopy (SEM). The two-polymer system demonstrates an excellent dielectric property (with values, ε?=?590 for composite gel versus 400 compare to virgin PVA). The nonfluid media exhibit the impulse DC bias polarization. The basic principle of this work is to understand and control the electrical parameters under external stimuli (field) response by Impedance tool. In the biomedical field, this gel may be an excellent supporting media for sonographic as one of the best polar medium.     

Properties of a gel polymer electrolyte based on lithium salt with poly(vinyl butyral)

Poly(vinyl butyral) (PVB) is of particular interest because of its low cost, extremely wide temperature work range (? 20 to 120 °C), and efficient chemical stability. In this study, a gel polymer electrolyte (GPE) containing Li⁺ ions was fabricated by using dimethylacetylamine (DMA), lithium perchlorate (LiClO₄), and PVB. The experimental results indicated that a highly transparent GPE with a high ionic conductivity (σ) could be obtained by mixing glue (DMA with a PVB content of 10 wt%) with a LiClO₄ content of 6 wt%. It was found that the ionic conductivity (σ) of the GPE depended on the LiClO₄ content, and the GPE with a LiClO₄ content of 6 wt% exhibited a maximum σ of 7.73 mS cm^?1, a viscosity coefficient of 3360 mPa s, and a transmittance greater than 89% (visible region) at room temperature. Furthermore, PVB improved the electrolyte solution leakage, and the LiClO₄ was used as an ion supply source for the high σ of the GPE.     

Study of a novel porous gel polymer electrolyte based on TPU/PVdF by electrospinning technique

Investigation on a new electrospun gel polymer electrolyte consisting of thermoplastic polyurethane (TPU) and poly(vinylidene fluoride) (PVdF) has been made. Its characteristics were investigated by scanning electron microscopy, FT-IR, Differential Scanning Calorimeter (DSC) analysis. This kind of gel polymer electrolyte had a high ionic conductivity about 3.2 × 10^− 3 S cm^− 1 at room temperature, and exhibited a high electrochemical stability up to 5.0 V versus Li⁺/Li, good mechanical strength and stability to allow safe operation in rechargeable lithium-ion polymer batteries. A Li/GPE/LiFePO₄ cell delivered a high discharge capacity when it was evaluated at 0.1 °C—rate at 25 °C (167.8 mAh g^− 1). And a very stable cycle performance also existed under this low current density.     

Nonlinear effects of non-Newtonian fluids on natural convection in a porous medium

This paper investigates the rheological effects of non-Newtonian fluids on the natural convection mechanism in a porous medium. A non-Newtonian behavior of power law fluid with a yield stress, saturating a porous medium, in which yield stress is temperature dependent, is considered. The cases of constant temperature boundary and constant heat flux boundary, along the heated vertical cylinder, are analyzed. The approximate similarity solutions in a closed form are shown, from which the velocity and temperature profiles are determined. The numerical solutions for a constant temperature boundary are also shown and discussed.     

Electrochemical characterization of ionic liquid based gel polymer electrolyte for lithium battery application

High molecular weight polymer poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-HFP), ionic liquid 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIMFSI), and salt lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)-based free-standing and conducting ionic liquid-based gel polymer electrolytes (ILGPE) have been prepared by solution cast method. Thermal, electrical, and electrochemical properties of 80 wt% IL containing gel polymer electrolyte (GPE) are investigated by thermogravimetric (TGA), impedance spectroscopy, linear sweep voltammetry (LSV), and cyclic voltammetry (CV). The 80 wt% IL containing GPE shows good thermal stability (~?200 °C), ionic conductivity (6.42?×?10^?4 S cm^?1), lithium ion conductivity (1.40?×?10^?4 S cm^?1 at 30 °C), and wide electrochemical stability window (~?4.10 V versus Li/Li⁺ at 30 °C). Furthermore, the surface of LiFePO₄ cathode material was modified by graphene oxide, with smooth and uniform coating layer, as confirmed by scanning electron microscopy (SEM), and with element content, as confirmed by energy dispersive X-ray (EDX) spectrum. The graphene oxide-coated LiFePO₄ cathode shows improved electrochemical performance with a good charge-discharge capacity and cyclic stability up to 50 cycles at 1C rate, as compared with the without coated LiFePO₄. At 30 °C, the discharge capacity reaches a maximum value of 104.50 and 95.0 mAh g^?1 for graphene oxide-coated LiFePO₄ and without coated LiFePO₄ at 1C rate respectively. These results indicated improved electrochemical performance of pristine LiFePO₄ cathode after coating with graphene oxide.     

A thermal and electrochemical properties research on gel polymer electrolyte membrane of lithium ion battery

N-methyl-N-propyl-piperidin-bis(trifluoromethylsulfonyl)imide/bis(trifluoromethylsulfonyl) imide lithium base/polymethyl methacrylate(PP₁₃TFSI/LiTFSI/PMMA) gel polymer electrolyte (GPE) membrane was prepared by in situ polymerization. The physical and chemical properties were comprehensively discussed. The decomposition characteristics were emphasized by thermogravimetric (TG-DTG) method in the nitrogen atmosphere at the different heating rates of 5, 10, 15 and 20 °C min⁻¹, respectively. The activation energy was calculated with the iso-conversional methods of Ozawa and Kissinger, Friedman, respectively, and the Coats-Redfern methods were adopted to employ the detailed mechanism of the electrolyte membrane. The equation f(α)=3/2[(1−α)^1/3−1] was quite an appropriate kinetic mechanisms to describe the thermal decomposition process with an activation energy (E_α) of 184 kJ/mol and a pre-exponential factor (A) of 1.894×10¹¹ were obtained.     

聚合物掺杂有机小分子发光二极管的电致发光与杂质陷阱效应

在新型空穴传输聚合物聚TPD(PTPD)中掺杂电子传输有机小分子荧光染料Rubrene制成薄膜器件.考察了不同掺杂浓度以及不同薄膜厚度器件的电致发光性能,结果表明存在杂质陷阱效应.基于固体中双注入理论，假设杂质陷阱限制在分立能级上，通过求解泊松方程，得到了掺杂器件J-V特性解析模型.该模型的计算值与实验结果一致.     

Efficient polymer white-light-emitting diodes with a single-emission layer of fluorescent polymer blend

Efficient polymer white-light-emitting diodes (WPLEDs) have been fabricated with a single layer of fluorescent polymer blend. The device structure consists of ITO/PEDOT/PVK/emissive layer/Ba/Al. The emissive layer is a blend of poly(9,9-dioctylfluorene) (PFO), phenyl-substituted PPV derivative (P-PPV) and a copolymer of 9,9-dioctylfluorene and 4,7-di(4-hexylthien-2-yl)-2,1,3-benzothiadiazole (PFO-DHTBT), which, respectively, emits blue, green and red light. The emission of pure and efficient white light was implemented by tuning the blend weight ratio of PFO: P-PPV: PFO-DHTBT to 96:4:0.4. The maximum current efficiency and luminance are, respectively, 7.6 cd/A at 6.7 V and 11930 cd/m² at 11.2 V. The CIE coordinates of white-light emission were stable with the drive voltages.     

Radiotracer diffusion and ionic conduction in a PEO-NaI polymer electrolyte

We studied ion transport in amorphous PEO30NaI consisting of poly(ethylene oxide) and sodium iodide in a Na-to-O ratio of 30. Diffusion coefficients of the radiotracers 22Na and 125I were measured for temperatures between 67 and 180 degrees C and compared with the overall charge diffusivity deduced from dc conductivity data. To explain the observed discrepancy between the sum of the tracer diffusivities and the charge diffusivity we propose a detailed model which is based on the formation of neutral ion pairs. Evaluating simultaneously all experimental data within this model yields not only the true diffusion coefficient of all individual species but also the ion-pairing reaction constant as a function of temperature.     

Nonlinear effects in the convective instability of a binary mixture in a porous medium near threshold

An amplitude equation is derived near threshold for both the stationary and the oscillatory instabilities and an oscillatory behavior in time for the Nusselt and the Froude number is predicted for the oscillatory instability.     

聚合物发光二极管中的负电容效应

采用交流阻抗谱技术,研究了以共轭聚合物(poly［2-methoxy,5-(2′-ethylhexoxy)-1,4-phenylenevinylene］)(MEH-PPV)为发光层,以带有胺基的聚芴共聚物poly［(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)］ (PF-NR₂)为电子传输层的发光二极管的交流响应特性. 对于结构为ITO/P 关键词： 2')" href="#">PF-NR₂ 聚合物发光二极管 交流阻抗谱 负电容效应     

The effects of ceramic fillers on the PMMA-based polymer electrolyte systems

The effects of ceramics fillers on the polymethylmethacrylate (PMMA)-based solid polymer electrolytes have been studied using ac impedance spectroscopy and infrared spectroscopy. The polymer film samples were prepared using solution cast technique, tetrahydrofuran (THF) used as a solvent, and ethylene carbonate (EC) has been used as plasticizer. Lithium triflate salt (LiCF₃SO₃) has been incorporated into the polymer electrolyte systems. Two types of ceramic fillers, i.e., SiO₂ and Al₂O₃, were then implemented into the polymer electrolyte systems. The solutions were stirred for several hours before it is poured into petri dishes for drying under ambient air. After the film has formed, it was transferred into desiccator for further drying before the test. From the observation done by impedance spectroscopy, the room temperature conductivity for the highest conducting film from the (PMMA–EC–LiCF₃SO₃) system is 1.36 × 10⁻⁵ S cm⁻¹. On addition of the SiO₂ filler and Al₂O₃ filler, the conductivity are expected to increase in the order of ∼10⁻⁴ S cm⁻¹. Infrared spectroscopy indicates complexation between the polymer and the plasticizer, the polymer and the salts, the plasticizer and the salts, and the polymer and the fillers. The interactions have been observed in the C=O band, C–O–C band, and the O–CH₃ band. Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7-9, 2006.     

Effect of NH4I and I2 concentration on agar gel polymer electrolyte properties for a dye-sensitized solar cell

Gel polymer electrolytes were prepared using agar polymer host, NH₄I, and I₂ salts. The sample of agar paste with 1.0 M of NH₄I and 0.2 μM of I₂ exhibits the highest conductivity and lowest viscosity values at room temperature of (2.64?±?0.19)?×?10^?3?S?cm^?1 and 1.17?±?0.29 Pa?s, respectively. All of the gel polymer electrolytes display Arrhenian behavior, and the optimum agar paste gave the lowest activation energy of 0.25 eV. It also had a good physical appearance compared with the other samples. This gel polymer electrolyte had a good potential and was applicable to a role as electrolyte in ITO-ZnO (N719 dye)/agar paste?+?1.0 M NH₄I?+?0.2 μM I₂/Au-Pd-ITO dye-sensitized solar cell.