A phosphate additive for poly(ethylene oxide)-based gel polymer electrolytes

The influence of an organophosphosphate additive on poly(ethylene oxide) lithium bis(trifluoromethylsulfonyl)imide-based gel polymer electrolytes for secondary lithium battery applications is described. Tris(2-(2-methoxyethoxy)ethyl)phosphate, is compared to the well known gel-battery component, propylene carbonate, through a study of complex impedance analysis, differential scanning calorimetry, and limiting oxygen index combustion analysis. The conductivities of the gels at low concentrations of tris(2-(2-methoxyethoxy)ethyl)phosphate (1.9–4.2 mol%) are higher to those of propylene carbonate-based systems with the same concentration. Despite micro-phase separation at high concentrations of tris(2-(2-methoxyethoxy)ethyl)phosphate (7.0–14.9 mol%), the conductivities remain comparable to systems that use propylene carbonate. The addition of tris(2-(2-methoxyethoxy)ethyl)phosphate to poly(ethylene oxide) gives increased fire retardance, while the addition of propylene carbonate to poly(ethylene oxide) results in increased flammability.     

Properties of nano-ZnO/poly(vinyl alcohol)/poly(ethylene oxide) composite thin films

A series of poly(vinyl alcohol)/nano-ZnO composites were prepared by dispersing nano-ZnO in aqueous solutions containing mixtures of the biodegradable polymers poly(vinyl alcohol) (PVA) and poly(ethylene oxide) (PEO), and composite thin films were prepared by casting. The introduction of nano-ZnO into PVA/PEO mixed solutions significantly decreased the resistivity of the solutions. Ultraviolet absorption, thermal behaviour and visco-elastic properties of the thin films were determined as a function of nano-ZnO content up to 15 wt%. Optimum film properties were obtained with 1 wt% nano-ZnO, higher proportions of nano-ZnO resulting in agglomeration of ZnO particles and deterioration in film properties. The Forouhi and Bloomer model was used for the modelling of ZnO thin films.     

Effect of tetrabutylammonium iodide content on PVDF-PMMA polymer blend electrolytes for dye-sensitized solar cells

The influence of tetrabutylammonium iodide on the polyvinylidene fluoride-poly(methyl methacrylate)-ethylene carbonate (PVDF-PMMA-EC)-I₂ polymer blend electrolytes was investigated and optimized for use in a dye-sensitized solar cell. The different weight ratios (50, 60, 70, and 80 %) of tetrabutylammonium iodide (TBAI)-added PVDF-PMMA-EC-I₂ polymer electrolytes were prepared. The prepared solid polymer blend electrolytes were characterized by using various techniques such as Fourier transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC), and electrochemical impedance spectroscopy (EIS). The FT-IR spectra revealed the interaction among all composition of polymer electrolytes. The influence of TBAI salt on the ionic conductivity of polymer electrolytes was studied using electrochemical impedance spectroscopy. The polymer electrolyte containing 60 % of TBAI in PVDF-PMMA-EC-I₂ showed the highest room temperature conductivity of 5.10?×?10^?3 S cm^?1. The fabricated DSSC using PVDF-PMMA-EC-I₂ polymer electrolytes with 60 % of TBAI showed the best performance with a short-circuit current density of 8.0 mA cm^?2, open-circuit voltage of 0.66 V, fill factor of 0.65, and the overall power conversion efficiency of 3.45 % under an illumination of 100 mW cm^?2. Hence, the weight content of organic iodide salt in polymer electrolytes influences the overall performance of dye-sensitized solar cells.     

Dielectric spectroscopy and viscosity studies of aqueous poly(ethylene oxide) and poly(vinyl pyrrolidone) blend

The complex dielectric function, electric modulus, impedance and ac electrical conductivity behaviour of aqueous solutions of 5 wt% poly(ethylene oxide) (PEO) and poly(vinyl pyrrolidone) (PVP) and their different volume percent blends were investigated in the frequency range 20 Hz to 1 MHz at 15, 30 and 45 °C. It is found that the real part of dielectric function of these blends at 1 MHz decreases with the increase of PEO concentration and their dc electrical conductivity has strong correlation with the electrode polarization relaxation time. The static permittivity, ionic conductivity, electrode polarization relaxation time and apparent viscosity have linear behaviour with temperature variation at fixed volume concentration of the aqueous polymers blend. The viscosity of these aqueous polymeric blends increases with the increase of PEO concentration. The behaviour of hydrogen bond interactions between the polar segments of PEO and PVP were explored from the comparative change in dielectric parameters and viscosity of the two phase aqueous polymeric systems.     

PEO electrolytes containing dioctyl phthalate (DOP) for dye-sensitized nanocrystalline TiO2 solar cells

In this paper, we aim to prepare polymer electrolytes consisting of NaI and I₂ dissolved in poly(ethylene oxide) (PEO) and dioctyl phthalate (DOP) as an additive and apply the electrolytes to dye-sensitized solar cells (DSSC). Upon the incorporation of salt, the phthalic-stretching C=O bands of DOP in Fourier transform infrared spectra shifted to a lower wave number (Δf = 93 cm⁻¹), confirming the unusual strong complex formation between sodium ions and phthalic oxygen. Coordinative interactions and structural changes of PEO/NaI/I₂/DOP electrolytes have also been characterized by wide angle X-ray scattering, presenting an almost amorphous structure of the polymer electrolytes. The ionic conductivity of the polymer electrolytes reached ∼10^–4 S/cm at room temperature at the mole ratio of [EO]:[Na]:[DOP] = 10:1:0.5, as determined by the four-probe method. DSSC using the polymer electrolytes and conductive indium tin oxide glasses exhibited 2.9% of overall energy conversion efficiency (=P _max/P _in × 100) at one sun condition (100 mW/cm²). The good interfacial contact between the electrolytes and the dye-attached nanocrystalline TiO₂ layers were verified by field-emission scanning electron microscopy.     

Characterization of poly(ethylene oxide) copper salt polymer electrolytes

The physico-chemical and electrochemical properties of a new class of polymer electrolytes formed by complexes of poly(ethylene oxide) and copper trifluorosulphonate salts have been investigated. The results suggest that these electrolytes are good copper ion conductors. Under particular conditions of concentration and temperature, and apparent electronic transport has also been evidenced.     

Conductivity and dielectric relaxation of Li salt in poly(ethylene oxide) and epoxidized natural rubber polymer electrolytes

Two types of polymer electrolytes were studied: poly(ethylene oxide) (PEO) and epoxidized natural rubber (ENR) both filled with lithium perchlorate. Universal dielectric behavior and impedance relaxation were investigated at room temperature over a wide range of salt concentration. Complex impedance plots exhibit one semicircle in some cases (PEO polymer electrolytes) with an extended spike at low frequencies. This implies a double layer capacity strongly influences conductivity at low frequencies. In the ENR–salt system, semicircles can be obtained only at very high concentrations. This points towards stable resistor dominated networks only develop at very high salt concentrations for this system. Centers of the semicircles lie below real axis indicating non-Debye dielectric relaxation. The relaxation peak broadens and shifts to higher frequencies with increasing salt content. It indicates that the relaxation time of polarization relaxations decreases with ascending salt content. Relaxations occur at extremely low salt concentrations in PEO and only at very high salt concentrations in ENR. Hence, conductivity of ENR–salt is one to two orders of magnitude lower as for PEO–salt.     

Alkaline poly(vinyl alcohol)/poly(acrylic acid) polymer electrolyte membrane for Ni-MH battery application

Ionics - Alkaline polymer electrolyte membrane with high ionic conductivity of 0.019 S cm−1 at room temperature was prepared from poly(vinyl alcohol) and acrylic acid...     

Vibrational and impedance spectroscopic analysis of poly(vinyl alcohol)-based solid polymer electrolytes

Solid polymer electrolytes based on poly(vinyl alcohol) (PVA) doped with NH₄Br have been prepared by the solution-casting method. The complex formation between the polymer and the salt has been confirmed by Fourier transform infrared spectroscopy. The highest conductivity at 303 K has been found to be of the order of 10⁻⁴ Scm⁻¹ for 25 mol% NH₄Br-doped PVA system. The ionic transference number of polymer electrolyte has been estimated by Wagner’s polarization method, and the results reveal that the conducting species are predominantly ions. Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006.     

Electrical,structural, and morphological studies of honeycomb-like microporous zinc-ion conducting poly (vinyl chloride)/poly (ethyl methacrylate) blend-based polymer electrolytes

Solid polymer electrolytes (SPEs) based on poly (vinyl chloride)/poly (ethyl methacrylate) [PVC/PEMA] blend complexed with zinc triflate [Zn(CF₃SO₃)₂] salt have been prepared using solution casting technique. Thin film samples containing various blend ratios of PVC/PEMA with fixed composition of salt have been examined by means of complex impedance analysis, and as a consequence, the typical composition corresponding to PVC (30 wt%)/PEMA (70 wt%) has been identified as the optimized blend exhibiting the highest room temperature ionic conductivity of 10^?8 Scm^?1. The ionic conductivity of the optimized blend was further enhanced from 10^?8 to 10^?6 Scm^?1 by adding the chosen salt in different weight percentages at 301 K. The occurrence of complexation of the polymer blend and an evidence of interaction of cations, namely Zn²⁺ ions with the polymer blend, have been confirmed by Attenuated total reflectance-Fourier transformed infrared (ATR-FTIR) spectroscopy measurement studies. The efficacy of ion-polymer interactions was estimated by means of an evaluation of transport number data pertaining to Zn²⁺ ions which was found to be 0.56. The apparent changes resulting in the structural properties of these polymer electrolytes possessing a honeycomb-like microporous structure were identified using X-ray diffraction (XRD) and scanning electron microscopic (SEM) studies. Such promising features of the present polymer blend electrolyte system appear to suggest possible fabrication of new rechargeable zinc batteries involving improved device characteristics.     

Mixed solid electrolytes based on poly(ethylene oxide)

Polymer solid electrolytes from a PEO-NaI system were mixed with Nasicon and Al₂O₃ powders. As a result an increase of ionic conductivity exceeding 10^–1 S/cm at room temperature was observed for both cases. This increase was due to a higher concentration of amorphous phase which resulted apparently from a higher nucleation rate during the solidification process. The samples were studied using impedance spectroscopy, X-ray diffraction, electron microscopy, NMR, and other techniques.     

Conductivity and thermal studies of blend polymer electrolytes based on PVAc–PMMA

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 T_g's for PVAc–PMMA blend. A decrease in T_g 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.     

Organic dopant added polyvinylidene fluoride based solid polymer electrolytes for dye-sensitized solar cells

The effect of phenothiazine (PTZ) as dopant on PVDF/KI/I₂ electrolyte was studied for the fabrication of efficient dye-sensitized solar cell (DSSC). The different weight percentage (wt%) ratios (0, 20, 30, 40 and 50%) of PTZ doped PVDF/KI/I₂ electrolyte films were prepared by solution casting method using DMF as a solvent. The following techniques such as Fourier transform infrared (FT-IR), differential scanning calorimetry (DSC), X-ray diffractometer (XRD) and AC-impedance analysis have been employed to characterize the prepared polymer electrolyte films. The FT-IR studies revealed the complex formation between PVDF/KI/I₂ and PTZ. The crystalline and amorphous nature of polymer electrolytes were confirmed by DSC and XRD analysis respectively. The ionic conductivities of polymer electrolyte films were calculated from the AC-impedance analysis. The undoped PVDF/KI/I₂ electrolyte exhibited the ionic conductivity of 4.68×10⁻⁶ S cm⁻¹ and this value was increased to 7.43×10⁻⁵ S cm⁻¹ when PTZ was added to PVDF/KI/I₂ electrolyte. On comparison with different wt% ratios, the maximum ionic conductivity was observed for 20% PTZ-PVDF/KI/I₂ electrolyte. A DSSC assembled with the optimized wt % of PTZ doped PVDF/KI/I₂ electrolyte exhibited a power conversion efficiency of 2.92%, than the undoped PVDF/KI/I₂ electrolyte (1.41%) at similar conditions. Hence, the 20% PTZ-PVDF/KI/I₂ electrolyte was found to be optimal for DSSC applications.     

Conductivity, dielectric behaviour and thermal stability studies of lithium ion dissociation in poly(methyl methacrylate)-based gel polymer electrolytes

Thin films of poly(methyl methacrylate) (PMMA) with lithium triflate (LiCF₃SO₃) were prepared by using the solution-casting method with PMMA as the host polymer. Ionic conductivity and dielectric measurements were carried out on these films. The highest conductivity for polymer electrolyte with a ratio of 65:35 was found to be 9.88 × 10⁻⁵ S cm⁻¹, which is suitable for the production of mobile phone battery. Thermal gravimetric analysis was carried out to evaluate the thermal stability of the polymer electrolyte. The addition of salts will increase thermal stability of the polymer electrolyte.     

A polymeric solid electrolyte based on a poly(ethylene oxide)/poly(bisphenol A-co-epichlorohydrin) blend with LiClO4

A polymeric solid electrolyte (PSE) based on a poly(ethylene oxide)/poly(bisphenol A-co-epichlorohydrin) (PEO/PBE) blend with LiClO₄ was obtained and characterized by its thermal, morphological, spectroscopic and electrochemical properties. DSC analysis showed suppression of PSE crystallinity for O:M lower than 32. The phase diagram exhibited four distinct regions, associated with the vitreous, viscoelastic and melt miscible phases, and a region where a viscoelastic and an immiscible vitreous phase are in equilibrium. Fourier transform infrared spectroscopy indicated complexation of the cation Li⁺ by both PEO and PBE oxygen atoms. Electrochemical impedance spectroscopy was used to characterize the ionic transport in the PSE at various temperatures and cyclic voltammetry provided information on the electrochemical stability window, which was found to be 5.5 V.     

Development of gel polymer electrolytes for application in quantum dot-sensitized solar cells

A methylcellulose–polysulfide gel polymer electrolyte has been prepared for application in quantum dot-sensitized solar cells (QDSSCs) having the configuration FTO/TiO₂/CdS/ZnS/SiO₂/electrolyte/Pt(cathode). The electrolyte with the composition of 30.66 wt.% methylcellulose, 67.44 wt.% Na₂S, and 1.90 wt.% sulfur exhibits the highest conductivity of 0.183 S cm^?1 with the lowest activation energy of 6.14 kJ mol^?1. CdS quantum dot sensitizers have been deposited on TiO₂ film via the successive ionic layer absorption and reaction (SILAR) method. The QDSSC fabricated using the highest conducting electrolyte and CdS QD prepared with five SILAR cycles exhibits a power conversion efficiency (PCE) of 0.78%. After deposition of zinc sulfide (ZnS) and silicon dioxide SiO₂ passivation layers, the PCE of the QDSSC with photoanode arrangement of TiO₂/CdS(5)/ZnS(2)/SiO₂ increased to 1.42%, an improvement in performance by 82%.     

An investigation of the proton conductivities of hydrated poly(vinyl alcohol)/boric acid complex electrolytes

Proton-conducting polymer complex electrolytes were prepared by incorporation of boric acid, H₃BO₃ into poly(vinylalcohol), PVA, to form hydrated PVAxH₃BO₃ where x denotes the number of moles of boric acid per polymer repeat unit. The dried materials were characterized via Fourier transform infrared spectroscopy, thermogravimetry, and X-ray diffraction. The proton conductivity of the hydrated complex electrolytes was measured by AC impedance spectroscopy. PVA2H₃BO₃ with RH ∼25% was found to be optimum composition that exhibited proton conductivity of 1.3 × 10⁻³ S/cm at 80 °C.     

Vibrational spectroscopy and structure of polymer electrolytes,poly(ethylene oxide) complexes of alkali metal salts

Complexes of poly(ethylene oxide) (PEO), with various alkali metal salts are known to exhibit ionic conductivities which exceed 10^?5(Ωcm)^?1 at moderate temperatures. We have employed IR and Raman spectroseopy to study well characterized samples of the following polymer-salt complexes: PEO·NaBr, PEO·NaI, PEO·NaSCN, PEO·NaBF₄, PEO·NaCF₃SO₃, PEO·KSCN, PEO·RbSCN and PEO·CsSCN. Cation-dependent vibrational bands observed in the far IR and M-O_n symmetric stretching bands observed in the Raman support a cation-oxygen atom interaction, and indicate the polyether chain may wrap around the cations. In particular, NaX and KX complexes of PEO are believed to have a helical configuration for the polymer which differs from that of pure PEO. Some general rules are presented for polymer-salt complex formation.     

Structural and electrical studies of sodium iodide doped poly(vinyl alcohol) polymer electrolyte films for their application in electrochemical cells

Solid polymer electrolyte films based on poly(vinyl alcohol) (PVA) complexed with sodium iodide (NaI) were prepared using solution cast technique. The structural properties of pure and complexed PVA polymer electrolyte films were examined by X-ray diffraction (XRD) studies. The XRD results revealed that the amorphous domains of PVA polymer matrix was increased with the increase in NaI salt concentration. The variation of film morphology was examined by scanning electron microscopy (SEM) studies. Fourier transform infrared spectral studies for pure and complexed PVA films revealed the vibrational changes that occurred due to the effect of dopant salt in the polymer. Direct current conductivity was measured in the temperature range of 303–373 K, and the conductivity was found to increase with the increase in dopant concentration as well as temperature. Measurement of transference number was carried out to investigate the nature of charge transport in these polymer electrolyte films using Wagner’s polarization technique. Transport number data showed that the charge transport in these polymer electrolyte systems was predominantly due to ions. Using these polymer electrolytes, solid-state electrochemical cells were fabricated. Various cell parameters like open-circuit voltage, short circuit current, power density, and energy density were determined.