Polymer Electrolyte

To prepare miscible polyethylene glycol diacrylate/polyvinylidene fluoride ͑PEGDA/PVdF͒ blend gel polymer electrolytes, low molecular weight (M ϭ 742) liquid PEGDA oligomer was mixed with PVdF-HFP dissolved in ethylene carbonate/dimethyl carbonate/LiPF 6 liquid electrolytes, and then cured under ultraviolet irradiation. Room temperature conductivity of PEGDA/PVdF blend films was found to be comparable to that of PVdF-HFP gel polymer electrolytes, and they were electrochemically stable up to 4.6 V vs. Li/Li ϩ. Scanning electron micrographs revealed that PEGDA/PVdF blend electrolytes have pore size intermediate between dense PEGDA and highly porous PVdF-HFP. It was confirmed by weight change measurement that liquid electrolyte was likely to evaporate through large pores in PVdF-HFP at 80°C, while PEGDA/PVdF blend showed better liquid electrolyte retention ability. This result was in good agreement with more stable interfacial properties of PEGDA/PVdF blend at 80°C in ac impedance analysis. Consequently, both PVdF-HFP and PEGDA/PVdF gel polymer electrolytes delivered similar discharge capacity at room temperature, but PEGDA/PVdF blend gel polymer electrolyte showed much better cycle performance than pure PVdF-HFP at 80°C.

The polymer electrolytes comprising blend of poly(vinyl acetate) (PVAc) and poly(methylmethacrylate) (PMMA) as a host polymer and LiClO4 as a dopant are prepared by solution casting technique. The amorphous nature of the polymer–salt complex has been confirmed by XRD analysis. The DSC thermograms show two Tg's for PVAc–PMMA blend. A decrease in Tg with the LiClO4 content reveals the increase of segmental motion. Conductance spectra results are found to obey the Jonscher's power law and the maximum dc conductivity value is found to be 1.76 × 10− 3 S cm− 1 at 303 K for the blend polymer complex with 20 wt.% LiClO4, which is suitable for the Li rechargeable batteries. The conductivity–temperature plots are found to follow an Arrhenius nature. The dc conductivity is found to increase with increase of salt concentration in the blend polymer complexes.

Electrochemical insertion of sodium ions into carbon using solid polymer electrolytes or organic liquid electrolytes is described. Cells with the configuration Na/P(EO)sNaCF3SOJCP(EO) = polyethylene oxide) or Na/liquid electrolyte/C were galvanostatically discharged, charged, and cycled. The extent of insertion into C (Le., x in Na § was found to be a strong function of the type and particle size of the carbon used, and the reversibility of the process was highly dependent upon the type of electrolyte used. The possibility of designing a sodium ion rocking chair cell is discussed, and a first-generation example, using a petroleum coke anode, polymer electrolyte, and sodium cobalt bronze cathode is described.

A comparative vibrational spectroscopy study is reported for a series of polymer electrolytes composed of poly(oligoethyleneoxy phosphazenes) containing dissolved lithium triflate. These polymers, of the form [NP((OCH 2 CH 2) x OCH 3) 2 ] n , with x=0, 1, 2, or 5, have been mixed with LiCF 3 SO 3 in oxygen:lithium concentration ratios ranging from 10:1 to 40:1. Raman vibrational spectroscopy has been used to examine ionic association and local changes of the polymer as the salt concentration and the length of the ethylene oxide side-chains vary. The degree of ionic association of the triflate ion increases with increasing salt concentration. At a given salt concentration, the degree of ionic association and the nature of the ion-polymer interaction are dependent on the length of the side-chains.

TiO 2 dye-sensitized solar cells (DSSCs) have been fabricated using TiO 2 photoelectrodes sensitized using the extracts of Delonix regia (May flower, locally called Vakai) and Eugenia Jambolana (Indian blackberry, locally called Naval) as natural sensitizers and their characteristics have been studied. Among them Eugenia Jambolana gave the best photosensitization effect and presents the prospect to be used as an environment-friendly, low-cost alternative system. The extracts having anthocyanin pigment (cyanidin 3-O-glucoside), which have carboxylic groups in the molecule can attach effectively to the surface of TiO 2 film. The solar cell constructed using the Eugenia Jambolana sensitized TiO 2 photo-electrode exhibited a short-circuit photocurrent of 1.49 mA and a power conversion efficiency of 0.5%.

The electrochemical, rheological, calorimetric, spectroscopic and morphological investigations have been used to examine poly(methyl methacrylate), PMMA based electrolytes dispersed with nano-sized fumed silica (SiO 2 ). The observed ionic conductivity was one of the highest and is of the order wmS/cm at ambient temperature which was studied as a function of concentration of fumed silica nano-particles. It was further found that the fumed silica acted as a passive filler and played a predominant role in controlling the rheological properties while ion transport properties were least effected. The differential calorimetry studies revealed single glass transition temperature pointing towards homogeneous nature of the composite polymeric electrolytes (CPEs). At an optimum concentration of fumed silica (2 wt%) the observed maximum conductivity and morphology was attributed to the presence of a strong network structure, while at a higher concentration the elastic behavior was more pronounced which impeded ion transport. This contention was supported by spectroscopic data. q .in (S.A. Agnihotry).

Gel Polymer Electrolytes (GPE) based on agar and containing LiClO4 have been prepared, characterized and applied to electrochromic devices. The ionic conductivity revealed the best result of 6.5 × 10−5 S/cm for the sample with 17 wt.% of LiClO4, which increased to 5.4 × 10−4 S/cm at 72°C. The GPE have been used in electrochromic devices (ECD) with K-glass/WO3/GPE/CeO2-TiO2/K-glass configuration. The ECD changed transmittance values up to 30% between the colored and transparent states. The charge density measurements revealed an increase of 5.5 to 7.5 mC/cm2 from the first to 500th cycles and then a decrease to 4.4 mC/cm2 during the next 4500 cycles. Coloration efficiency (η) of 25 cm2/C was obtained.

Electrochromic evacuated advanced glazing has been developed, combining optimum dynamic control of the solar radiation penetrating into buildings with a high degree of thermal insulation. This was achieved by the optimisation of the electrochromic device materials (electrochromic, ion storage, protective layers, transparent conductors and polymer electrolytes) and by the refinement of a sealing method for evacuated glazing. Electrochromic evacuated glazing prototypes with dimensions up to 40 cm  40 cm have been fabricated using vacuum techniques and chemical methods. The prototypes exhibit excellent optical and thermal performance, with a contrast ratio up to 1:32 (visible dynamic transmittance range T lum,bleached = 63% and T lum,colored = 2%), coloration efficiency up to 92 cm 2 /C and mid-pane U-values as low as 0.86 W m À2 K À1 . Their durability in relation to real working environmental conditions has been assessed through indoor and outdoor testing. Such a glazing can be used in building applications to improve occupant thermal comfort, contribute to a reduction in space heating and cooling loads and allow for increased areas of fenestration thereby reducing artificial lighting loads. These factors reduce the energy demand for the building and therefore contribute to the reduction of carbon dioxide emissions. #

We present a study of impedance spectroscopy (IS) under varying loads. An equivalent circuit is proposed taking the deformability and the effect of change in free volume into account, which yields the dc ion-conductivity as well as the Young's modulus from these results. Independent measurements of elastic properties are done and the result is compared with Young's modulus predicted from IS. The sample we studied is PEO-NH 4 ClO 4 with a salt fraction of 0.19 by weight, with frequencies varying in the range of 40 Hz to 3 MHz and loads varying from 400 to 1600 g.

8 MeV EB irradiation effect on dielectric constant and AC conductivity of polymer electrolyte films was observed. Occurrence of chain scission due to breaking of bonds was confirmed by FT-IR analysis. AC conductivity increases with dose due to more number of free charges involved in conduction.

A series of different composition of polymer electrolytes-based on poly(vinyl chloride) (PVC) as host polymer, lithium tetraborate (Li 2 B 4 O 7 ) as dopant salt, and dibutyl phthalate (DBP) as plasticizer were prepared by solution casting method. The interaction between the PVC, Li 2 B 4 O 7 , and DBP were studied by Fourier transform infrared. The shifting, broadening, and splitting of transmission peaks were the evidences of complexation. The highest ionic conductivity polymer electrolyte of 2.83× 10 −6 S/cm was achieved at ambient temperature upon addition of 30 wt.% of DBP. In addition, the temperaturedependent conductivity, frequency-dependent conductivity, dielectric permittivity, and modulus studies were performed. The temperature-dependent conductivity of the polymer electrolytes was found to obey the Arrhenius behavior. The thermal stability of polymer electrolytes was verified by thermogravimetric analysis. The lower in glass transition temperature was proven in differential scanning calorimetry, whereas the higher amorphous region within the polymer matrix was demonstrated in X-ray diffraction.

A new type of single-ion conductor with fixed cation was synthesized by spontaneous anionic polymerization of 4-vinylpyridine in the presence of short polyethylene oxide (PEO) chains as alkylating agents. These comblike polymers have low T g s and are amorphous with the shorter PEOs. Their conductivities are unaffected by the nature of the anion (Br 0 , ClO 0 4 , and tosylate) and are controlled by the free volume and the mobility of the pendant cation. By comparison of the results at constant free volume, it is shown that the charge density decreases with the increasing length of pendant PEO demonstrating that PEO acts only as a plasticizing agent. Best conductivity results ( s Å 10 05 S cm 01 at 60ЊC) are obtained with PEO side chains of molecular weight 350. With this sample, the conductivity in the presence of various amounts of added salt (LiTFSI) was studied. A best value of 10 04 S cm 01 at 60ЊC is obtained with a molar ratio EO/Li of 10. It is shown that, over the range of examined concentrations (0.2-1.3 mol Li kg 01 ), the reduced conductivity s r /c increases linearly with increasing salt concentration showing that the ion mobility increases continuously. Such behavior is quite unusual since in this concentration range a maximum is generally observed with PEO systems. To interpret this result and by analogy with the behavior of this type of polymer in solution, it is proposed that the conformation of these polymers in the solid state is segregated with the P4VP skeleton more or less confined inside the dense coils surrounded by the PEO side chains. Under the influence of the increasing salt concentration, this microphase separation vanishes progressively: The LiTFSI salt exchanges with the tosylate anions and acts as a miscibility improver agent.

A new approach to electrochromics, based on the reversible coating-dissolution of an oxide from an inorganic electrochromic electrolyte consisting of a silver-amine complex in a polymer electrolyte (PEO), has proven successful. The reversible electrodeposition of silver onto indium-tin oxide coated glass (ITO) was investigated and the influence of HClO 4 and KI was evaluated. Several characteristics of the electrolyte Ag-PEO make it suitable for use in electrochromic reversible silver electrodeposition devices, such as visible absorption spectrum with an absorbance variation of 60%, an electrochromic efficiency of 5.2 cm 2 C −1 and an ionic conductivity 4.4 × 10 −4 S cm −1. The addition of perchloric acid improved the transparency of Ag-PEO, and potassium iodide (KI) was fundamental in setting up the process of reversible silver electrodeposition in the PEO polymeric matrix. A description of the electrochemical processes implied is presented. A number of approaches focusing on the improvement of system performance are tested.

high-capacitance dielectrics that serve as gate insulators in organic thin-film transistors are a particular priority. Solid polymer electrolytes (a salt dissolved in a polymer matrix) have been investigated for this purpose, but they suffer from slow polarization response, limiting transistor speed to less than 100 Hz. Here, we demonstrate that an emerging class of polymer electrolytes known as ion gels can serve as printable, high-capacitance gate insulators in organic thin-film transistors. The specific capacitance exceeds that of conventional ceramic or polymeric gate dielectrics, enabling transistor operation at low voltages with kilohertz switching frequencies.

Work demand for energy is expected high and finding sufficient route to produce clean energy is an ever more pressing problem. Science had identified the key research challenges if solar energy is to provide a significant fraction of our energy needs. The huge gap between our present use of solar energy and its enormous undeveloped potential defines a grand challenge in energy research. One of the most attractive methods currently being developed is ''dye sensitization'' in solar cells in order to increase the efficiency of conversion of solar radiation into electricity. Although large improvements in present technology will be required, the review points to progress in nanoscience, in particular as a reason to be optimistic. r 2007 Published by Elsevier B.V.

Simultaneous impedance measurements and optical observations of polymer electrolytes were conducted in an automated experimental setup, combining an impedance analyser, polarizing microscope with a heating stage and a digital camera. The polymer film was placed between glasses with indium tin oxide conductive layers, forming a transparent cell mounted in a custom-designed holder, which preserved an argon atmosphere. Results of in-situ studies for various compositions of poly(ethylene oxide) (PEO) with LiN(CF 3 SO 2 ) 2 salt (LiTFSI), as well as pure PEO, are presented. In the investigated systems, crystallization had a strong impact on ionic conductivity. It was found that the initial growth of crystalline structures caused only a small fraction of the total decrease of conductivity. A large decrease in conductivity was observed during the second stage of crystallization, when no significant changes in microscope picture were observed. In pure PEO and the PEO:LiTFSI 6:1 system, a dense crystalline structure developed, resulting in a decrease in conductivity of over two orders of magnitude. In dilute PEO:LiTFSI systems, a "loose" structure was formed, with amorphous areas preserved between crystallites, and conductivity decreased by only a factor of about 6.

Lithium polymer electrolytes formed by dissolving a lithium salt LiX in poly(ethylene oxide) PEO may find useful application as separators in lithium rechargeable polymer batteries. The main problems which are still to be solved for a complete successful operation of these materials are the reactivity of their interface with the lithium metal electrode and the decay of their conductivity at temperatures below 708C. In this paper we demonstrate that a successful approach for overcoming these problems is the dispersion of selected, low-particle size ceramic powders in the polymer mass with the aim of developing new types of nanocomposite PEO-LiX polymer electrolytes characterized by enhanced interfacial stability as well as by improved ambient temperature transport properties.

The electrical properties of solvent-free, PEO-LiTFSI solid polymer electrolytes (SPEs), incorporating different N-alkyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide, PYR 1A TFSI, ionic liquids (ILs), are reported. For this purpose, PYR 1A TFSI materials containing side alkyl groups with different chain-length and branching, i.e., n-propyl, sec-propyl, n-butyl, iso-butyl, sec-butyl and n-pentyl, were properly synthesized and homogeneously incorporated into the SPE samples without phase separation. The addition of ILs to PEO-LiTFSI electrolytes results in a large increase of the conductivity and in a decrease of the interfacial resistance with the lithium metal anode. Most of the PEO-LiTFSI-PYR 1A TFSI samples showed similar ionic conductivities (>10 −4 S cm −1 at 20 • C) and stable interfacial resistance values (400 cm 2 at 40 • C and 3000 cm 2 at 20 • C) upon several months of storage. Preliminary battery tests have shown that Li/P(EO) 10 LiTFSI + 0.96 PYR 1A TFSI/LiFePO 4 solid-state cells are capable to deliver a capacity of 125 mAh g −1 and 100 mAh g −1 at 30 • C and 25 • C, respectively.

Solid polymer electrolytes based on poly (vinyl alcohol) (PVA) complexed with sodium fluoride (NaF) at different weight percent ratios were prepared using solution cast technique. The structural properties of these electrolyte films were examined by XRD studies. The XRD data revealed that the amorphous domains of PVA polymer matrix increased with increase of NaF salt concentration. The complexation of the salt with the polymer was confirmed by FT-IR studies. Electrical conductivity was measured in the temperature range of 303-373 K and the conductivity was found to increase with the increase of dopant concentration as well as temperature. The dielectric constant (e 0 ) increased with the increase in temperature and decreased with the increase in frequency. A loss peak was identified at 365 K in the dielectric loss spectra and is attributed to the orientation of polar groups. Measurement of transference number was carried out to investigate the nature of charge transport in these polymer electrolyte films using Wagner's polarization technique and Watanabe technique. Transport number data showed that the charge transport in these polymer electrolyte systems was predominantly due to ions and in particular due to anions. Using these polymer electrolytes, solid state electrochemical cells were fabricated. Various cell parameters like open circuit voltage (OCV), short circuit current (SCC), power density and energy density were determined.

As a potential electrolyte for lithium-ion batteries, a porous polymer electrolyte membrane based on poly(vinylidenefluoride-hexafluoropropylene) (PVDF-HFP) was prepared by a phase inversion method. The casting solution, effects of the solvent and non-solvent and addition of micron scale TiO 2 particles were investigated. The membranes were characterized by SEM, XRD, AC impedance, and charge/discharge tests. By using acetone as the solvent and water as the non-solvent, the prepared membranes showed good ability to absorb and retain the lithium ion containing electrolyte. Addition of micron TiO 2 particles to the polymer electrolyte was found to enhance the tensile strength, electrolyte uptake, ion conductivity and the electrolyte/electrode interfacial stability of the membrane. , in the polymer electrolyte . Usually, these inorganic fillers are dispersed in the polymer electrolyte in the form of nanoparticles, however, nanoparticles tend to aggregate because of the high surface energy. For example, Kim et al. reported that TiO 2 nanoparticles cannot be well dispersed, even under conditions such as ultrasonication and the subsequent ball-milling. In this study, the (PVDF-HFP)-based PSPE was prepared by the phase inversion method. The preparation process of the casting solution and effects of solvent and non-solvent on the configuration and performance have been investigated. The influence of micron particles of TiO 2 incorporated in PSPE on the structure and properties of PSPE have been examined.

Fuel cells (FCs) are mainly applied for electricity generation. This paper presents a review of specific FCs with ability to produce useful chemicals at the same time. The chemical cogeneration processes have been classified according to the different types of fuel cells. Thus, it is shown that a flow alkaline FC (AFC) is able to produce hydrogen peroxide. In aqueous acid or neutral FCs, hydrogenations, dehydrogenations, halogenations and oxidations, together with pollution abatement solutions, are reported. Hydrogen peroxide and valuable organic chemicals can also be obtained from polymer electrolyte FCs (PEFCs). A phosphoric acid FC (PAFC) allows the selective oxidation of hydrocarbons and aromatic compounds, and the production of industrial compounds such as cresols. Molten salt FCs (similar to molten carbonate or MCFCs) can be applied to obtain acetaldehyde with high product selectivity from ethanol oxidation at the anode. Solid oxide FCs (SOFCs) are able of chemical cogeneration of valuable industrial inorganic compounds such as nitric oxide with high yields. Although the number of related papers in the literature is small, the potential economic interest of this emergent field, related to the recent commercial development of fuel cells, is demonstrated in some cases, and the corresponding results encourage the development of FCs with electrocogeneration of useful chemicals with high added value and electricity.

Solid polymer electrolyte (SPE) water electrolysis is analyzed by a simple model based on Butler-Volmer kinetics for electrodes and transport resistance in the polymer electrolyte. An equivalent electrical circuit analogy is provided for the sequential kinetic and transport resistances. The model provides a relation between applied terminal voltage of the electrolysis cell and current density in terms of Nernst potential, exchange current densities, and conductivity of polymer electrolyte. The overpotentials and resistances at the anode, cathode, and overpotential due to ohmic resistances are individually analyzed and are in good agreement with experimental results. The reduction kinetics at the cathode is relatively fast while the anodic overpotential is mainly responsible for the voltage drop.

The aim of the present work is to demonstrate that an efficient all solid electric double layer capacitor (EDLC) may be realised with electrolyte membrane and carbon based electrodes prepared by using a Nafion ionomer solution. Polymer membrane was prepared by a casting method. Electrodes were prepared with two overlapped layers formed of a carbon Á/Nafion layer and a carbon paper substrate. Three different electrolyte separators in capacitor configuration have been tested and compared: (1) a commercial Nafion 115 membrane (N115), (2) a membrane prepared by casting the Nafion 1100 solution (NRG50) and (3) a porous glass fibre matrix impregnated with a 1 M H 2 SO 4 solution (FVH2SO4). The membrane and electrodes assemblies (MEA) had thickness of 0.6 Á/ 0.8 mm and geometric area of 4 cm 2 . The EDLCs characteristics have been studied by conductivity, cyclic voltammetry and DC charge Á/discharge methods. Proton conductivities of 5.7 )/10 (2 and 3.1 )/10 (2 S cm (1 have been measured at room temperature for the N115 and the NRG50, respectively. Specific capacity of 13.2 F g (1 has been obtained by capacitor utilising the cast Nafion membrane. This value is 70% of specific capacity obtained from the capacitor using sulphuric acid and about 140% of that using Nafion 115. #

The polymer electrolytes are promising materials for the ever-growing need for high energy density power sources for power and traction applications. With an emphasis on lithium batteries, the field of polymer electrolytes has gone through a sort of three stages; dry solid systems, polymer gels, and polymer composites. The 'polymer gels' and the 'polymer composites', the former incorporating organic solvents, have shown room temperature conductivities as high as 10 y3 S cm y1 .The 'dry solid systems' presently suffer from poor ionic Ž y5 y1 . conductivities ; 10 S cm at 208C , but are safer than the former due to absence of any organic solvent which can cause environmental hazards. In the area of electrode systems, one can notice quite good performances by the organo-sulfur polymers as Ž .

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Polymer electrolytes, generally, are all those materials where a supramolecular system is doped with ions and presents a significant conductivity. Following the 12th and most recent International Symposium of Polymer Electrolytes (ISPE-12), this historical and critical review summarizes the main developments in the fundamental science and applications of this family of materials since their establishment approximately 40 years ago. The history of polymer electrolytes is briefly outlined and the main families are reviewed in the framework of a tentative classification scheme. The applications of polymer electrolytes are discussed, highlighting the role of the electrolyte materials and reporting the most widely accepted performance and durability benchmarks in the various fields. Finally, a statistical analysis of the available scientific literature is presented to identify the most relevant current trends and future possibilities in the diversification and growth of worldwide research on this topic.

Polymer electrolyte-based unitized reversible fuel cells (URFCs) combine the functionality of a fuel cell and an electrolyzer in a single device. In a URFC, titanium (Ti)-felt is used as a gas diffusion layer (GDL) of the oxygen electrode, whereas typical carbon paper is used as a GDL of the hydrogen electrode. Different samples of Ti-felt with different structural properties (porosity and fiber diameter) and PTFE content were prepared for use as GDLs of the oxygen electrode, and the relation between the properties of the GDL and the fuel cell performance was examined for both fuel cell and electrolysis operation modes. Experimental results showed that the cell with a Ti-felt GDL of 80μm fiber diameter had the highest round-trip efficiency due to excellent fuel cell operation under relatively high-humidity conditions despite degradation in performance in the electrolysis mode.

Poly (N-vinyl pyrrolidone) (PVP) and ammonium thiocyanate (NH4SCN) based polymer films with different compositions have been prepared by solution casting technique. The amorphous nature of the polymer electrolytes has been confirmed by XRD analysis. The FTIR analysis confirms the complex formation of the polymer with the salt. The conductivity analysis shows that the 20 mol% ammonium thiocyanate doped polymer electrolyte has high ionic conductivity and it has been found to be 1.7 × 10−4 S cm−1, at room temperature. From the admittance plot, the activation energy has been found to be low for 20 mol% salt doped polymer electrolyte. The dielectric behavior has been analyzed using dielectric permittivity (ε∗), dissipation factor (tan δ) and electric modulus (M∗) of the samples.

The electrochemical and ion transport properties of heterogeneous electrolyte mixtures are reviewed. The review is restricted to lithium ion conducting electrolytes and to electrolytes containing at least one polymer component. Different electrolytetypes are compared, and lithium batteries based on the eletrolytes are described.

An improved polymer electrolyte membrane fuel cell-based amperometric hydrogen sensor has been developed. The sensor operates at room temperature, and the electrolyte used in the sensor is Nafion which is a protonconducting solid polymer electrolyte. Platinum black is used as both anode and cathode. The sensor functions as a fuel cell, H 2 /Pt//Nafion//Pt/O 2 , and a mechanical barrier limits the supply of hydrogen to the sensing side electrode. The limiting current is found to be linearly related to the hydrogen concentration. The sensor can be used to measure hydrogen in argon in parts per million and percentage levels. The basic principle, details of assembly, and response behavior of the sensor are discussed.

Recent studies show that the SEt on lithium and on LiXC6 anodes in liquid nonaqueous solutions consists of many different materials including Li20, LiF, LiCI, Li2C03, L1CO2-R, alkoxides, and nonconducting polymers. The equivalent circuit for such a mosaic-type SEI electrode is extremely complex. It is shown that near room temperature the grain-boundary resistance (R96) for polyparticle solid electrolytes is larger than the bulk ionic resistance. Up to now, all models of SEt electrodes ignored the contribution of R6b to the overall SEI resistance. We show here that this neglect has no justification. On the basis of recent results, we propose here for SEI electrodes equivalent circuits which take into account the contribution of grain-boundary and other interfacial impedance terms. This model accounts for a variety of different types of Nyquist plots reported for lithium and LiC6 electrodes in liquid nonaqueous and polymer electrolytes.

A series of cross-linked network polysiloxanes containing oligoethylene oxide units, (OCH 2 CH 2 ) n , as internal free chains have been synthesized by performing hydrosilylation of partially PEO-substituted polysiloxane precursor with a, N-diallyl terminated poly(ethylene glycol). The polymer electrolytes were formed by complexing with LiN(CF 3 SO 2 ) 2 electrolyte salt and exhibited superior conductive property. The r RT of the network polymer electrolytes is in the range of 2.50 Â 10 À 5 to 1.62 Â 10 À 4 S/cm and depends on the cross-linking density (in terms of Si -H amount of the siloxane precursor), repeating unit number of internal oligoethylene oxide and chain length of the cross-linker. The significant enhancement of the conductivity was observed when low molecular weight dimethyl poly(ethylene glycol) was added as plasticizer. The temperature dependence of the ionic conductivity was also studied, following the Vogel -Tamman -Fulcher (VTF) equation. D

Gel polymer electrolyte Sago Oxygen consumption a b s t r a c t The electrochemistry of a direct borohydride fuel cell based on a gel polymer electrolyte was studied. Sago is a type of natural polymer, was employed as the polymer host for the electrolyte. An electrolyte with a composition of sago þ 6 M KOH þ 2 M NaBH 4 was prepared and evaluated as a novel gel polymer electrolyte for a direct borohydride fuel cell system because it exhibited a high electrical conductivity of 0.270 S cm À1 . The rate at which oxygen was consumed at the cathode can be related to the electric current by comparing the calculated number of electrons reacted per molecule of oxygen for different currents supplied to the fuel cell. From the oxygen consumption data, it was deduced that four electrons reacted per molecule of oxygen. The performance of the fuel cell was measured in terms of its currentevoltage, discharge and open circuit voltage measurements. The maximum power density obtained was 8.818 mW cm À2 at a discharge performance of w230 mA h and nominal voltage of 0.806 V. The open circuit voltage of the cells was about 0.900 V and sustained for 23 h. .my (A.A. Mohamad).

Polymer electrolytes, (PEO:LiClO 4 )þx IL (1-Buty-3methylimidazolium hexafluorophosphate) with varying concentration of IL; x ¼ 0,5,10,15,20 wt % have been prepared by solution cast technique and characterized by X-Ray diffraction, differential scanning calorimetery, FTIR, conductivity and dielectric relaxation measurements in the frequency range of 100 Hz-5 MHz. Temperature dependence of relaxation frequency and conductivity were found to be typical of thermally activated process both at T > T m and T < T m . Composition dependence of conductivity, dielectric relaxation, and degree of crystallinity has also been studied. On addition of IL, the degree of crystallinity after a decrease at 5 wt % IL increases slightly at 10 wt % and then finally decreasing. Variation of conductivity and relaxation frequency with composition could only be partly explained on the basis of variation of degree of crystallinity. An additional feature of ion-ion interaction (contact ion pair formation between IL or salt cations and their associated anions) has been invoked which was supported by FTIR studies.

A plasticized polymer electrolyte system composed of PVDF-HFP, potassium iodide (KI), and equal weight of ethylene carbonate (EC) and propylene carbonate (PC) has been used in a dye-sensitized solar cell (DSSC). The electrolyte with the composition 40 wt. % PVDF-HFP-10wt. % KI-50 wt. % (EC + PC) exhibits the highest room temperature ionic conductivity of 1.10 x 10(-3) S cm(-1). A small amount of iodine crystal of about 10 wt. % of KI was added to the electrolyte in the liquid state to provide the redox couple for DSSC operation. The polymer electrolyte films were prepared by the solvent casting method. The DSSCs were fabricated with the electrolyte film sandwiched between a TiO(2)/dye photoelectrode and a Pt-counter electrode and characterized under 100 mW cm(-2) white light. The DSSC performance with different dyes such as Ruthenizer 535 (N3), anthocyanin, chlorophyll, and a mixture of anthocyanin and chlorophyll (v/v = 1) has been compared. The DSSC with Ruthenizer 535 (N3) dye exhibits the best performance with a short-circuit current density of 8.16 mA cm(-2), open-circuit voltage of 0.76 V, fill factor of 0.35, and photoconversion efficiency of 2.2%.

Composite electrolyte films consisting of poly(vinylchloride), poly(acrylonitrile), ethylene carbonate, LiClO4 and also TiO2 particles have been prepared by solution casting technique. The effect of inorganic filler on the conductivity of the blended polymer electrolyte was studied. A conductivity of (7.57 × 10−5 S cm−1) is achieved at room temperature for the composition PVC–PAN–LiClO4–EC (4.8–19.2–8–68), whereas it improves two orders of magnitude (4.46 × 10−3 S cm−1) upon dispersing fine particles of TiO2 as inert filler. The role of ceramic phase is to reduce the melting temperature which is ascertained from the thermogravimetric/differential thermal analysis.

Today, special interest is focused on polymer systems showing high ionic conductivity at ambient and/or sub ambient temperatures, since they find unique practical applications, such as separators in high power, versatile, rechargeable Li-based batteries. Thermo-set membranes prepared by free radical photo polymerisation (UV-curing) could be an interesting alternative to existing polymer electrolytes. In the present paper, we report the application of this technique to the synthesis of gel-polymer membranes which can be used as electrolytes for lithium battery application. These membranes are prepared by mixing a dimethacrylic (BEMA) and/or a diacrylic monomer (PEGDA), a methacrylic reactive diluent (PEGMA) and a radical photo-initiator with the in situ addition of a EC/DEC solution. The above mixtures are UV irradiated to obtain transparent, flexible, easy to handle gel-polymer films. The gel-polymer electrolytes (GPEs) are then prepared by swelling these membranes in different liquid electrolytes. The results obtained indicate some superior and satisfactory performances in terms of ionic conductivity at ambient temperature for various GPEs prepared with different lithium salt solutions. The relevance of these features in view of practical application is here demonstrated by the response of lithium cells based on prepared GPEs.

Gel polymer electrolytes (GPEs) made of blends of ionic liquids and polymer elements, are of high interest as electrolytes in batteries. They possess the high mechanical stability and non-fluidity of solids, together with the thermal and electrochemical stabilities of ionic liquids. In the present work we studied GPE, comprised of a EMI·(HF) 2.3 F ionic liquid and 2-hydroxyethyl methacrylate polymer. Morphological characteristics, thermal, electrical, and electrochemical studies confirmed the ability of the GPE to serve as an electrolyte in an all solid Si-air battery. The ionic transport number, determined via the Wagner polarization technique, was found to be close to unity, suggesting ionic conduction domination over an electrical conduction. GPE containing 70 mol% ionic liquid showed a discharge voltage of 0.6 V over more than 850 h, in a discharge current of 0.1 mA cm −2 . This work demonstrates the feasibility of using gel polymer electrolytes in silicon-air batteries that offer unprecedented specific energy for powering low power devices.

Two types of photolectrochemical (PEC) solar cells, FTO/TiO 2 /dye/PAN, EC, PC, Pr 4 N + I À , I 2 /Pt/FTO, and FTO/TiO 2 /dye/PEO, EC, PC, KI/I 2 /Pt/FTO have been fabricated using a PAN-based gel polymer electrolyte and a PEO-based plasticised polymer electrolyte. The PAN-based gel electrolyte, made of polyacrylonitrile (PAN), ethylene carbonate (EC), propylene carbonate (PC) and tetrapropylammoniumiodide (Pr 4 N + I À ) as the complexing salt exhibited a room temperature conductivity of 2.9 Â 10 À1 S m À1 for the composition, PAN (13%):EC (31%):PC (45%):Pr 4 N + I À (7%):I 2 (4%) by weight ratio. The PEO-based polymer electrolyte had a conductivity of 2.2 Â 10 À3 S cm À1 for the composition PEO (37.5%):EC (37.5%):PC (20.7%):KI (3.9%):I 2 (0.4%). These solar cells have been characterised using current-voltage characteristics and action spectra. The PAN-based solar cells had an overall quantum efficiency of 2.3%. However, the PEO-based solar cells had an overall quantum efficiency of only 0.6%. r

Due to energy crises in the future, much effort is being directed towards alternate sources. Solar energy is accepted as a novel substitute for conventional sources of energy. Out of the long list of various types of solar cells available on the market, solid state photoelectrochemical solar cells (SSPECs) and dye sensitized solar cells (DSSCs) are proposed as an alternative to costly crystalline solar cell. This review provides a common platform for SSPECs and DSSCs using polymer electrolyte, particularly on polyethylene oxide (PEO)-based polymer electrolytes. Due to numerous advantageous properties of PEO, it is frequently used as an electrolyte in both SSPECs as well as DSSCs. In DSSCs, so far high efficiency (more than 11%) has been obtained only by using volatile liquid electrolyte, which suffers many disadvantages, such as corrosion, leakage and evaporation. The PEO-based solid polymer proves its importance and could be used to solve the problems stated above. The recent developments in SSPECs and DSSCs using modified PEO electrolytes by adding nano size inorganic fillers, blending with low molecular weight polymers and ionic liquid (IL) are discussed in detail. The role of ionic liquid in modifying the electrical, structural and photoelectrochemical properties of PEO polymer electrolytes is also described.

In situ polymerization of pyrrole was carried out in the presence of fly ash (FA) to synthesize polypyrrole-fly ash composites (PPy/FA) by chemical oxidation method. The PPy/FA composites have been synthesized with various compositions (10, 20, 30, 40 and 50 wt%) of fly ash in pyrrole. The surface morphology of these composites was studied with scanning electron micrograph (SEM). The polypyrrole-fly ash composites were also characterized by employing X-ray diffractometry (XRD) and infrared spectroscopy (IR). The a.c. conductivity behaviour has been investigated in the frequency range 10 2 -10 6 Hz. The d.c. conductivity was studied in the temperature range from 40-200°C. The dimensions of fly ash in the matrix have a greater influence on the observed conductivity values. The results obtained for these composites are of greater scientific and technological interest.

A new solvent-free composite polymer electrolyte consisting of poly(ethylene oxide) (PEO) incorporated into diphenyl amine (DPA) along with KI and I 2 has been developed. The current-voltage characteristics of this nanocrystalline dye-sensitized solar cell measured under simulated sunlight with 1.5 AM at 60 mW/cm 2 have indicated that this cell generates a photocurrent of 10.2 mA/cm 2 , together with a photovoltage of 810 mV and fill factor of 0.47 yielding an overall energy conversion efficiency of 6.5%. This result suggests that the electron donicity of DPA influences the interaction of nanocrystalline TiO 2 electrode and I À /I 3 À electrolyte, leading to a high performance of the fabricated solar cell.

Gel polymer electrolytes composed of PVdF / HFP and a non-aqueous lithium electrolyte solution EC / DEC / LiN(C F SO ) (BETI) were prepared to investigate the conduction properties of the gel materials. Structural and 2 5 2 2 micro-structural characterization was carried out by means of modulated differential scanning calorimetry (MDSC) and scanning electron microscopy (SEM). The samples with polymer / solution weight ratios higher than 0.5 contain at least an amorphous swollen gel phase and a crystalline one, while a pure liquid phase appears, which occupies cavities in the micrometer range in the gels with lower polymer content. The transport properties of the gels were investigated by means of impedance spectroscopy for conductivity and pulsed-field gradient nuclear magnetic resonance (PFG-NMR) for diffusion coefficients. The results were compared with those of corresponding films prepared with LiN(CF SO ) (TFSI). The 3 2 2 BETI-based samples showed diffusion values lower than the TFSI-based ones. Estimation of the carrier concentration change with the gel composition revealed that the interaction between the host polymer and the electrolyte in the gel especially in the polymer rich region ( . 50 wt%).

In this manuscript is reported an attempt to prepare high ionic conductivity lithium polymer electrolytes by UV cross-linking the poly(ethyleneoxide) (briefly called PEO) polymer matrix in presence of the plasticizing lithium salt, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and an ionic liquid of the pyrrolidinium family (N-alkyl-N-methylpyrrolidinium TFSI) having a common anion with the lithium salt. It is demonstrated that polymer electrolytes with room temperature ionic conductivities of nearly 10 −3 S cm −1 could be obtained as a result of the reduced crystallinity of the ternary electrolytes. The results clearly indicate that the cross-linked ternary electrolyte shows superior mechanical properties with respect to the non-cross-linked electrolytes and higher conductivities with respect to polymer electrolytes containing none or less ionic liquid.

The influence of compact layer of TiO 2 between FTO and nano-porous TiO 2 on the charge transport and photovoltaic properties of quasi-solid state dye sensitized solar cells with polymer gel electrolyte and perylene derivative dye as sensitizer was investigated. The PEDOT:PSS/graphite/FTO was used as counter electrodes for present investigation. The modification of photo-electrode significantly improve the power conversion efficiency (2.94%) of the solar cells attributed to the higher electron lifetime and reduction in recombination processes as indicated by the electro-chemical impedance spectra of the solar cell. The compact layer provide a large TiO 2 /FTO contact area, reduce the electron recombination by blocking the direct contact with the redox couple in the electrolyte and efficient collection of electrons by FTO electrode. Finally, the incorporation of TiO 2 nano-particle in the polymer electrolyte further improves the power conversion efficiency (3.2%) of the device attributed to the improved ion transport.