Amorphous Polymer Electrolytes Research Articles

Differential Anomalous X-ray Scattering from an Amorphous Polymer Electrolyte: [PPO]xZnBr2

Differential anomalous X-ray scattering (DAS) and extended X-ray absorption fine structure (EXAFS) were used to determine the local structure surrounding the ions in amorphous polymer electrolyte complexes of poly(propylene oxide) and ZnBr 2 : [PPO] 6 ZnBr 2 and [PPO] 16 ZnBr 2 . On the basis of our results, we propose that ZnBr 2 dissociates to form mainly ZnBr 4 2- and Zn(O) 4 2+ , where (O) is an ether oxygen on a PPO chain. This observation is contrasted with aqueous ZnBr 2 , where ZnBr 2 , ZnBr 3 - , and ZnBr 4 2- are all observed in the estimated proportions of 2:4:3, respectively. This paper describes the DAS method and its application to structure determination in a multicomponent, amorphous system. In systems with n components, where one or more of the species is a heavy atom, DAS reduces the scattering intensity from a weighted sum of n(n+1)/2 partial structure factors to a sum of partial structure factors which only include the heavy atom of interest

Conductivity behaviour of modified polysiloxane-Nal polymer complexes

Polymer electrolytes have received attention in the past decade because of their promise in applications such as solid state batteries, gas sensors and electrochromic displays. Over the years, polyoxyethylene (POE) based electrolytes have been widely studied and used because of their excellent mechanical stability, superior solvating power and chain flexibility, which gives them an unsurpassed conductivity at high temperatures, usually above 60 °C [1]. However, their strong semicrystalline nature below 60 °C leads to a drastic reduction in conductivity at ambient temperatures and limits their application to temperatures above 60 °C. It is well known that conduction in polymer-salt complexes takes place in the amorphous domains only [1]. Hence, the objective of the current research is twofold: firstly, to develop an amorphous polymer electrolyte, and, secondly, to achieve a high ambient temperature conductivity. Various techniques such as reduction in crystallinity, reduction in glass transition temperature (Tg), using different salts and varying the salt concentration have been proposed [1] in order to improve the conductivity. The objective, while attempting the modifications, is not to compromise on the solvating and mechanical properties offered by the oxyethylene (OE) group. The solution is to synthesize a comb-like polymer with an amorphous backbone and POE side chains of optimum length to impart mechanical strength. Such comb-like structures have been reported for both poly(phosphazenes) [2, 3] and polysiloxanes [4, 5], and are found to give room temperature conductivities of the order of 10 .5 (f~ cm) -1, which is two orders of magnitude higher than those for POE-based electrolytes. Polysiloxanes are valued primarily for their low Tg (~ -123 °C) and outstanding thermo-oxidative stability. Conductivity results from previous studies are encouraging [6, 7]. This letter investigates the conductivity behaviour of polysiloxane-sodium iodide polymer electrolytes. The polymer studied here contains a polysiloxane backbone with randomly substituted side chains composed of three EO monomeric units, as shown in Fig. 1. This polymer (number average molecular weight -750 000 g) was complexed with NaI salt (Loba-Chemie, GR, molecular weight = 149.89 g) and the polymer electrolyte films were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), infrared (IR) spectroscopy and optical microscopy. The effect of NaI concentration was studied by varying the O/Na ratio. For all of the compositions

Ion Pairing and Ionic Conductivity in Amorphous Polymer Electrolytes: a Structural Investigation Employing EXAFS

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTIon Pairing and Ionic Conductivity in Amorphous Polymer Electrolytes: a Structural Investigation Employing EXAFSDavid W. Pollock, Kelly J. Williamson, Kara S Weber, Leslie J. Lyons, and Lee R. SharpeCite this: Chem. Mater. 1994, 6, 11, 1912–1914Publication Date (Print):November 1, 1994Publication History Published online1 May 2002Published inissue 1 November 1994https://doi.org/10.1021/cm00047a004RIGHTS & PERMISSIONSArticle Views148Altmetric-Citations6LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (378 KB) Get e-Alerts Get e-Alerts

Synthesis and electrochemical characterization of new bulky lithium salts

We describe the synthesis of new lithium salts, based on bulky carbanions, substituted by strong electron withdrawing groups together with their electrochemical studies using high molecular weight host polymer poly(oxyethylene) POE. The ionic conductivities of lithium salts-POE complexes have been measured as a function of temperature by impedance spectroscopy. The new lithium salts exhibit a wide electrochemical window stability. Their dissolution in POE ( M w=5×10 6) provides amorphous polymer electrolytes with high ionic conductivity.

Lithium-7 NMR and ionic conductivity studies of gel electrolytes based on polyacrylonitrile

Composite gel electrolytes prepared from mixtures of poly(acrylonitrile) (PAN), ethylene carbonate (EC), propylene carbonate (PC), and LiClO[sub 4] or LiAsF[sub 6] have been investigated by complex impedance, differential scanning calorimetry (DSC), and [sup 7]Li nuclear magnetic resonance (NMR) spectroscopy. The ionic conductivity of a gel containing LiAsF[sub 6] reaches 10[sup [minus]2] S/cm at 60[degrees]C. Although the conductivity of the gels approach that found in EC/PC liquid electrolytes, NMR line width, and spin-lattice relaxation time (T[sub 1]) measurements indicate that even short-range ionic mobility is impeded by the presence of the PAN. As in the case of amorphous polyether-salt polymer electrolytes, the onset of [sup 7]Li motional line narrowing in the gels is strongly correlated with the DSC-determined glass transition temperature. 6 figs., 1 tab.

Ionic conductivity and dynamic mechanical relaxation of a two-component epoxy network-LiClO 4 electrolyte system

The correlation between mechanical relaxation and ionic conductivity was investigated in a two-component epoxy network-LiClO 4 electrolyte system. The network was composed of diglycidyl ether of polyethylene glycol (DGEPEG) and triglycidyl ether of glycerol (TGEG). The effects of salt concentration, molecular weight of PEG in DGEPEG and the proportion of DGEPEG (1000) in DGEPEG/TGEG ratio on the ionic conductivity and the mechanical relaxation of the system were studied. It was found that, among the three influential factors, the former reinforces the network chains, reduces the free volume fraction and thus increases the relaxation time of the segmental motion, which in turn lowers the ionic conductivity of the specimen. Conversely, the latter two increase the free volume and thus the chain flexibility, showing an opposite effect. From the iso-free-volume plot of the shift factor log a T and reduced ionic conductivity, it is noted that the plot can be used to examine the temperature dependence of segmental mobility and seems to be useful to judge whether the incorporated salt has been dissociated completely. Besides, the ionic conductivity and relaxation time at constant reference temperature are linearly correlated with each other in all the three cases. This result gives an additional experimental confirmation of the coordinated motion model of the ionic hopping with the moving polymer chain segment, which is generally used to explain the ionic conduction in non-glassy amorphous polymer electrolytes.

Cation and anion diffusion coefficients in a solid polymer electrolyte measured by pulsed-field-gradient nuclear magnetic resonance

Diffusion of Li+-based and PF6--based species in an amorphous polymer electrolyte has been explored by pulsed-field-gradient (PFG) nuclear magnetic resonance. The experiments were undertaken over a range of salt concentrations and temperature extending to lower values of both variables than in previous studies. Features of the results include a demonstration of different mechanisms for anion and cation transport at high concentration, as shown by their different temperature dependences, a reduced sensitivity of cation diffusion to salt concentration and a failure of the Nernst-Einstein relationship. Cation hopping between ionic clusters and the diffusion of neutral ion pairs are advanced as microscopic mechanisms to explain the data.

Synthesis and electrochemical characterization of new polymer electrolytes based on dioxolane homo and co-polymers

Several polyacetals have been investigated as host polymer, for polymer electrolytes. The cationic polymerization and copolymerization of dioxolane (DXL) and 4-methyl, dioxolane (MDXL) are reported. If PDXL is a semi-crystalline polymer, an amorphous polymer electrolyte at room temperature is obtained for some LiTFSI concentrations. The PMDXL as well as the copolymer Poly(DXL-MDXL) appear completely amorphous. Nevertheless, due to salt desolvation or polymer degradation, the PMDXL/LiTFSI conductivities drop when the temperature increases.

Ionic motions in network polymers containing lithium perchlorate

Amorphous network polymer electrolytes were derived from poly(propylene oxide) and tris(4-isocyanatophenyl)thiophosphate complexed with lithium perchlorate. The complex impedance diagrams of the higher crosslink density samples were found to be a superposition of two semicircles having different relaxation times. On the other hand, the diagrams of the lowest crosslink density samples were a single semicircle. The Cole-Cole equation was employed to evaluate the relaxation parameters. The higher frequency process was assigned to ionic motions associated with segmental motions of the propylene oxide chain, and the lower frequency process was assigned to ionic motions associated with segmental motions of the urethane group. Dynamic mechanical thermal spectra show two relaxation peaks in the higher cross-link density samples and T 1 ϱ as a function of temperature obtained by 7Li n.m.r. study has a well defined minimum. These results indicate the correlation between the ionic mobility and the molecular motions of the network system.

Effect of additive salts on ion conductivity characteristics in solid polymer electrolytes

Effects of lattice energy of the additive salt on ionic species and ion conductivity characteristics were studied in the solid polymer electrolyte. Poly[oligo(oxyethylene) methacrylate] and several lithium salts were used as matrix and additive salt for solid polymer electrolytes, respectively. Salt and salt content deeply affected the ion conductivity characteristics as well as morphology even for amorphous type solid polymer electrolytes. The relationship between ion conductivity at constant reduced temperature ( T − T g = 90°C) and lattice energy of the additive salt was evaluated at each salt content. A different relationship was found for each salt content. Multiple ion aggregate formation was considerably affected by the salt, and was revealed to be effective to increase the ion conductivity.

Ionic conductivity mechanism of network polymers containing lithium perchlorate

Amorphous network polymer electrolytes were derived from poly(propylene oxide) (PPO) and phenyl isocyanate complexed with lithium perchlorate. Two ionic relaxation processes were found in the complex impedance spectra. Dynamic mechanical spectra showed two relaxation peaks in the high cross link density samples and T1 P as a function of the temperature obtained by 7Li-NMR study has a well defined minimum. The peak position and the half width of D-LAM band obtained by FT-Raman spectra were found to depend on the salt concentration. These results strongly suggest the interaction of lithium cation and network chains.

NMR spectroscopy of peo-based polymer electrolytes

The temperature dependence of proton NMR spectra and spin-lattice relaxation has been studied for poly(ethylene oxide) films (PEO) and for PEO films containing M(CF 3SO 3) 2PEO n with MZn and Pb and n in the range 9–24. In the pure PEO films, the chain mobility of the crystalline and amorphous parts may be studied separately because of their very different relaxation behaviour. When the triflate salts are dissolved in PEO, both spectra and relaxation change their behaviour dramatically. This is a result of the chain mobility being considerably reduced in these largely amorphous polymer electrolyte films.

Nmr Studies of Polymer Electrolytes

AbstractThe results of several investigations of solvent-free polymer electrolytes by nuclear magnetic resonance (NMR) spectroscopy conducted by the authors and other groups are reviewed. 23Na NMR spectra of a wide variety of amorphous polymer electrolytes are characteristic of the second-order quadrupole broadened central ± 1/2 transition with a distribution of quadrupole couplings. The temperature dependence of the linewidth is similar across a wide range of materials, and highlights the importance of polymer segmental motions above the glass transition temperature to ion mobility. Strong cation-anion interactions in poly(propylene oxide) complexes are indicated by measurements of mobile ion concentrations and, in some cases, the observation of salt precipitation at elevated temperature.

High Pressure Conductivity and NMR Investigation of Siloxane-Based Polymer Electrolytes

Abstract Variable temperature and pressure conductivity and 23Na nuclear magnetic resonance (NMR) measurements of several siloxane-based polymers complexed with NaCF3SO3 are reported. The conductivity exhibits V.T.F. behavior of the type commonly observed in amorphous polymer electrolytes, and activation volumes (29.9 cm3/mol at 313K for one sample) typical of these materials. The NMR linewidths associated with mobile Na+ ions exhibit motional narrowing above Tg in a manner similar to other Na-polymer electrolytes. The pressure dependence of the 23Na linewidth is consistent with a 10-15 K/kbar increase in Tg.