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.     

Morphology and conductivity of electrolytes based on poly(ethylene oxide) - Eu(ClO4)3 films

Solid polymer electrolytes based on a poly(ethylene oxide), (PEO), host have been prepared using the solvent casting method and characterized by conductivity measurements and thermal analysis. The observed ionic conductivity of the novel system based on PEO and europium perchlorate was similar to that of other electrolytes based on the same polymer host with a different trivalent guest species [1]. The presence of the perchlorate anion widened the composition range of amorphous behaviour but limited the thermal stability of the electrolytes produced. Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997     

Effect of fillers on magnesium–poly(ethylene oxide) solid polymer electrolyte

A solid polymer electrolyte (SPE) film consisting of poly(ethylene oxide) (PEO) with magnesium chloride as electrolytic salt and B₂O₃ as the filler has been prepared by solution casting technique. The polymeric film was flexible and self-standing with proper mechanical strength and studied for application in a solid-state rechargeable magnesium battery. The interactions between the filler and PEO chains are studied by differential scanning calorimeter and Fourier transform infrared techniques. Composition of SPE is optimized, and maximum conductivity is obtained at 2 wt% B₂O₃. Filler seems to increase the number of free magnesium cations by decoordinating the bond between magnesium cations and ether oxygen of PEO. Cyclic voltammetry results show the reversible capability of magnesium electrode. Solid-state magnesium cell employing magnesium anode, SPE, and manganese oxide was assembled, and its open circuit voltage is found to be 1.9 V.     

Crystallization kinetics and crystal morphology in thin poly(ethylene oxide) films

We present a detailed study of the kinetics of crystallization for thin films of poly(ethylene oxide) (PEO). Measurements of the growth rate have been carried out using optical-microscopy techniques on films of monodisperse PEO. Films with thicknesses from 13 nm to ~2 m were crystallized isothermally at temperatures ~20°C below the melting point. A remarkable non-monotonic slowing-down of the crystal growth is observed for films with thickness less than ~400 nm. The changes in the growth rate from bulk-like values is significant and corresponds to a factor of 40 decrease for the thinnest films studied. The morphologies of isothermally crystallized samples are studied using atomic-force microscopy. We find that a morphology, similar to diffusion-controlled growth (dendritic growth and densely branched growth), is observed for films with h < 150 nm. In addition, changes in the morphology occur for thicknesses consistent with changes in the growth rate as a function of film thickness.     

Direct-current conductivity of poly(ethylene terephthalate)

There have been several previous studies of the dc conductivity of poly(ethylene terephthalate). Disagreement among the various authors indicates the difficulties inherent in this measurement: several authors [1,2] found evidence for ionic conduction through a hopping process; others [3,4] proposed conduction by electrons injected through a barrier.     

Ionic conductivity of electrolytes based on star-branched poly(ethylene oxide) with high concentration of lithium salts

Electrolytes based on star-branched poly(ethylene oxide) with lithium bis(trifluoromethanesulfone)imide LiTFSI and lithium iodide salts were prepared by casting from solution. The electrical properties of electrolytes subjected to various heating and cooling runs were studied by impedance spectroscopy and impedance spectroscopy simultaneous with optical microscope observation. Differential scanning calorimetry was used for additional characterization. The results indicate that in electrolytes with high content of salt, values of ionic conductivity comparable to that of dilute electrolytes can be achieved. Moreover, electrolytes with high amount of salt seem to show weaker temperature dependence of conductivity. Promising results in terms of ionic conductivity were obtained for mixture of LiTFSI and lithium iodide. A few problems which may decrease the performance of studied system as a solid electrolyte were also identified, from which changes of physical properties of samples subjected to thermal cycles and aging seem to be the most important ones.     

Ionic conductivity and electrochemical stability of poly(methylmethacrylate)-poly(ethylene oxide) blend-ceramic fillers composites

The role of inorganic ceramic fillers namely nanosized Al₂O₃ (15-25 nm) and TiO₂ (10-14 nm) and ferroelectric filler SrBi₄Ti₄O₁₅ (SBT CIT) (0.5 μm) synthesized by citrate gel technique (CIT) on the ionic conductivity and electrochemical properties of polymer blend 15 wt% PMMA+PEO₈:LiClO₄+2 wt% EC/PC electrolytes were investigated. Enhancement in conductivity was obtained with a maximum of 0.72×10⁻⁵ S cm⁻¹ at 21 °C for 2 wt% of SrBi₄Ti₄O₁₅ (SBT CIT) composite polymer electrolyte. The lithium-ion transport number and the electrochemical stability of the composite polymer electrolytes at ambient temperature were analyzed. An enhancement in electrochemical stability was observed for polymer composites containing 2 wt% of SrBi₄Ti₄O₁₅ (SBT CIT) as fillers.     

Synthesis and morphological change in poly(ethylene oxide)-sodium chlorate based polymer electrolyte complex with polyaniline

The composites of polyethylene oxide:polyaniline:sodium chlorate is prepared by stirring with anhydrous acetonitrile for 5-6 h to form homogeneous solutions/gels at different weight percentages. The composites are characterized by FTIR and SEM. The predominant peaks that appeared in FTIR spectra confirm the formation of PEO:PANI:NaClO₄ composites. It is found from the SEM studies that there is a significant change in the morphology of various weight percentages of NaClO₄ in PEO-PANI matrix, i.e. from ellipsoidal to square. DC conductivity behavior is seen due to hopping of polarons from one localized state to another that can be confirmed by Mott theory. It is observed from the DC conductivity and SEM studies that these composites can be promising candidates for solid state electrolytes.     

Conductance study of poly(ethylene oxide)- and poly(propylene oxide)-based polyelectrolytes

The ionic conductivity of poly(ethylene oxide) and poly(propylene oxide) in pure solution form, individually complexed with salts of Na⁺ and Li⁺, with and without plasticizer (propylene carbonate) and in blended form with individual salt with and without plasticizer, was studied. The conductance measurements were made at various concentrations of salt polymer complexes and at different temperatures. The effects of temperature and plasticizer concentration were measured from Arrhenius conductance plots. It is shown that the addition of salts in pure PEO increases conductance many times. The plasticizer has also same effect. The blending of PEO with PPO gives enhanced conductivity as compared to pure PEO. The activation energies were determined for all the systems which gave higher values for pure PEO and the value decreases with the addition of Li and Na salts and further decreases with the addition of plasticizer. The blending has also lowered the activation energy values which mean that incorporation of PPO in PEO has decreased crystallinity and the amorphous region has increased the local mobility of polymer chains resulting in lower activation energies.     

Stimuli-responsive poly(ethylene oxide)-b-poly(2-vinylpyridine)-b-poly(ethylene oxide) triblock copolymers and complexation with poly(acrylic acid) at low pH

The self-organization of the double hydrophilic triblock copolymer poly(ethylene oxide)-b-poly(2-vinylpyridine)-b-poly(ethylene oxide), PEO-b-P2VP-b-PEO, was investigated in dilute aqueous solution under several experimental conditions using turbidimetry, as well as static and dynamic light scattering. As a result of the temperature-sensitive properties of the end PEO blocks and the p H-responsive properties of the middle P2VP block, the formation of large star-like micellar nanostructures is observed at high p H, while at low p H, but in the presence of salt and at high temperature, flower-like micelles are formed. Moreover, the viscosimetric and dynamic light scattering studies at low p H revealed that micelle-like nanostructures are formed upon mixing the triblock copolymer with poly(acrylic acid), PAA, due to hydrogen bonding interpolymer complexation.     

An experimental study on the effect of mesoporous silica addition on ion conductivity of poly(ethylene oxide) electrolytes

Solid polymer electrolyte (SPE) composites, which are composed of poly(ethylene oxide) (PEO), mesoporous silica (SBA-15), and lithium salt were prepared in order to investigate the influence of SBA-15 content on the ionic conductivity of the composites. The ionic conductivity of the SPE composites was monitored by frequency response analyzer (FRA), and the crystallinity of the SPE composites was evaluated by using XRD. As a result, the addition of SBA-15 to the polymer mixture inhibited the growth of PEO crystalline domain, due to the mesoporous structure of the SBA-15. Also, the PEO₁₆LiClO₄/SBA-15 composite electrolytes show an increased ion conductivity as a function of SBA-15 content up to 15 wt.%. These ion conductivity characteristics are dependent on crystallinity with SBA-15 content.     

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.     

Single-molecule single crystals of poly(ethylene oxide)

Single-molecule single crystals were prepared from two fractions of poly(ethylene oxide) (PEO) with narrow molar mass distribution and an equimolar mixture of the two fractions. It was proven that the molar mass distribution of the single-molecule single crystals from the mixed sample corresponds to an addition of those of the pure fractions. Well-shaped crystals were obtained after isothermal crystallization or on annealing. A variety of morphologies typical for multimolecule single crystals of PEO were found and are described on the basis of the various known modes of twinning. The results are in agreement with the known unit cell of PEO.     

Auger spectroscopy of polyethylene and poly (ethylene oxide)

The X-ray excited Auger spectra of polyethylene and poly(ethylene oxide) have been corrected for Auger electron energy losses due to interactions with the solid and compared to the corresponding spectra of gas phase molecular analogs. The corrected polyethylene spectrum is an extrapolation of trends observed in the spectra of gas phase alkanes from CH₄ through C₆H₁₄. The O(KVV) spectrum of poly(ethylene oxide) is similar to that of methyl ether, consistent with similar nearest neighbor environments for the oxygen atoms in the two materials. In contrast, the C(KVV) spectrum of poly(ethylene oxide), a material which contains C-C bonds, is better approximated by the spectrum of ethane (H₃C-CH₃). A comparison of the polyethylene Auger spectrum with the spectra of the normal alkanes and with a self-fold of its X-ray excited valence band photoemission (single hole) spectrum indicates the presence of correlated two-hole final states in the case of polyethylene.     

Characterisation of poly(ethylene oxide) sulfonic acids

PEO sulfonic acids with M_w in the range 446–4246 have been prepared. Mechanically stable polyelectrolyte films containing high molar mass PEO and PEO sulfonic acids were prepared. The PEO sulfonic acids and the polyelectrolyte films were examined by thermal analysis, optical microscopy, Raman spectroscopy, and impedance spectroscopy. While the low molar mass PEO sulfonic acids were completely amorphous, sulfonic acids with M_w ≥ 1246 show considerable crystallinity. Experimental data indicate aggregation of the low molar mass PEO sulfonic acids through hydrogen bonds. The PEO sulfonic acids are miscible with high molar mass PEO and form free standing polyelectrolyte films. The PEO sulfonic acids with the lowest molar masses have a plasticizing effect on the high molar mass PEO. The crystallinity of the films decreased as the concentration of sulfonic acid increased. The films are stable at RH ≤ 75%, and for some mixtures protonic conductivities of 10⁻³ S cm⁻¹ at room temperature were reached.     

The compatibility and morphology of chitosan-poly (ethylene oxide) blends

Thermal behavior and morphology of blends prepared by solution casting of mixtures of chitosan and poly(ethylene oxide) were studied by means of differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The preliminary results indicate that both melting point and crystallinity depend on the composition of the blends, and that they exhibit minimum values when the blend contains 50% chitosan. From the prediction of melting point depression analysis, the compatibility of the blends shows a transition at this specific composition. This conclusion was further confirmed by observation of the morphology.     

Environmental effects on the ionic conductivity of poly(methyl methacrylate) (PMMA)-based quasi-solid-state electrolyte

Quasi-solid-state dye-sensitized solar cells (QS-DSSCs) using polymer electrolytes display excellent long-term stability with comparable light to electricity conversion efficiency (PCE). In this paper, poly(methyl methacrylate) (PMMA) is chosen as the template polymer, and polymer viscosity and its weight percentage of PMMA in the I₃ ^?/I^? electrolyte system are optimized considering the competitive factors of the ionic conductivity (σ) and gel dimension stability. A systematic study is carried out to study the environmental factors on the ionic conductivity of quasi-solid electrolytes in terms of storage time, thermal stress, and light soaking. In the different temperature range, the polymer presents different aggregation states and molecular motion forms, which results in different conductive mechanism of the gel electrolyte. It could be described by the Arrhenius equation in the sol state and the Vogel–Tammann–Fulcher (VFT) equation on the gel state, respectively. Both the cyclic voltammetry curve and the Tafel polarization curve indicate that the quasi-solid electrolyte exhibits a lower ion diffusion and transport capacity (1.83?×?10^?6 cm²/s) than that of the liquid electrolyte (9.15?×?10^?6 cm²/s). This work provides new insights about the degradation mechanism of polymer electrolytes for QS-DSSC application.

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Electrical and structural properties of poly (ethylene oxide)/silver triflate polymer electrolyte system dispersed with MgO nanofillers

Solvent-free films of poly (ethylene oxide)–silver triflate (PEO–AgCF₃SO₃)/MgO-based nanocomposite polymer electrolytes (PEO)₅₀AgCF₃SO₃–x wt.% MgO (x = 1, 3, 5, 7, and 10) obtained using solution casting technique were found to exhibit an appreciably good complexation of MgO nanofiller within the polymer electrolyte system and non-Debye type of relaxation as revealed by Fourier transform infrared and complex impedance analyses. Optimized filler (5 wt.% MgO) when incorporated into the polymer electrolyte resulted in a maximum electrical conductivity of 2 × 10⁻⁶ S cm⁻¹ in conjunction with a silver ionic transference number (t _Ag+) of 0.23 at room temperature (298 K). Detailed structural, thermal, and surface morphological investigation indicated a slight reduction in the degree of crystallinity owing to the addition of MgO nanofiller.     

Effects of poly(ethylene glycol) on electrical conductivity of poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonic acid) film

A series of poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonic acid) composite thin films with prescribed concentrations of poly(ethylene glycol) were prepared. The PEDOT–PSS pristine film and PEDOT–PSS/PEG films were studied using four-probe method, photoelectron spectroscopy and atomic force microscopy. The electrical conductivity of PEDOT–PSS/PEG hybrid films was found to be enhanced compared to the PEDOT–PSS pristine film, depending on the PEG concentration and molecular weight. XPS analysis and AFM results showed that PEG induces the phase separation between the PEDOT–PSS conducting particles and the excessive PSSNa shell. Simultaneously PEG may form hydrogen bond with sulfonic groups of PSSH, and hence weaken the electrostatic interactions between PEDOT cationic chains and PSS anionic chains. These resulted in the creation of a better conduction pathway among PEDOT–PSS particles, attributed to the improvement of conductivity.