摘要:

AbstractWe review the effects of temperature on conductance and viscosity in the liquid state of vitreous ionic conductors and show how differences may be best understood by comparison ofrelaxation timesfor electrical and mechanical stresses acting on liquid or glassy states of the material. This leads to the definition of a conductivity/viscosity modedecoupling index, useful as a figure of merit for the solid electrolyte. In applying the same approach to polymer electrolyte systems a problem is encountered due to the molecular weight dependence of the viscosity. This is resolved by deriving a ‘monomer’ shear relaxation time for the polymer electrolyte solution and showing that this quantity corresponds closely with the ‘local’ mechanical relaxation time obtained from light scattering studies (which is a molecular weight independent quantity for pure polypropylene oxide and other polymers of lowTg). Comparison of the electrical relaxation times of the polymer solution with the ‘local’ (or ‘matrix’) relaxation times then shows that the relationship found for superionic glass‐forming systems is inverted in the case of polymer electrolytes. The latter have fractional decoupling indexes which may be interpreted in terms of serial coupling phenomena; i.e. ions must first decouple from their partner ions (in ion pairs), or from their intramolecular solvation states, before they can contribute to conductivity relaxation which is itself coupled to the local polymer matrix relaxation. An extreme case is illustrated using the weak electrolyte, lithium acetate, for which the decoupling i

ISSN:0007-1641    

DOI:10.1002/pi.4980200303

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractPolymer electrolytes are solvent‐free ion‐conducting polymers and provide new and attractive materials in both polymer chemistry and electrochemistry. A proper understanding of ion dissociation and ion transport in such polymers is necessary for their application as solid electrolytes in electrochemical devices. Ionic conduction behaviour in polymer electrolytes is described here in relation to the characteristic properties. Of special interest is the ability of polymer electrolytes to include various kinds of electroactive molecules within them. The combination of this ability with their high ionic conductivity has enabled polymer electrolytes to be used as media for electrochemical syntheses and redox reacti

ISSN:0007-1641    

DOI:10.1002/pi.4980200304

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractA new solid polymer electrolyte, poly(ethylene oxide)‐Hg(ClO4)2, has been prepared with the ratio of ethylene oxide units to mercury ions ranging from 4 to 20. The variation of conductivity with temperature does not follow a simple Arrhenius law. At high salt concentrations the films are entirely amorphou

ISSN:0007-1641    

DOI:10.1002/pi.4980200305

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractDifferential scanning calorimetry (d.s.c.) and electrical conductivity measurements of poly(propylene oxide), PPO, complexed with the salts NaI and KSCN are reported. In addition,23Na n.m.r. measurements on PPO‐NaI (x = 8), both at ambient and elevated pressure (2 kbar), have been performed. The d.s.c. data clearly indicate that the salt precipitates out of the complexes at about 85°C for NaI and 60°C for KSCN. These effects are manifested by a dramatic departure of the conductivity from Vogel‐Tammann‐Fulcher (VTF) behaviour, and a relatively sharp drop in mobile Na+concentration, as deduced from n.m.r. measurements, above about 80°C. High pressure n.m.r. linewidth measurements are consistent with a pressure‐induced increase in glass transition t

ISSN:0007-1641    

DOI:10.1002/pi.4980200306

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractSolutions of alkali metal thiocyanates in liquid copolymers of ethylene oxide and propylene oxide provide a convenient medium for measuring conductivities, viscosities and transport numbers in polymer electrolytes by classical methods. The high value of the anion transport number (typicallyca.0.95) is noteworthy. A model, which emphasises the importance of intramolecular solvation of cations, the effects of ion pairing and redissociation, and the crosslinking action of anions at high salt concentrations, accounts satisfactorily for the properties of these liquid systems.

ISSN:0007-1641    

DOI:10.1002/pi.4980200307

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractConductivity and n.m.r. measurements are reported for three poly(ethylene oxide)‐inorganic salt complexes: PEO‐LiCF3SO3‐NaI ([EO]/[Li]/[Na] = 8/1/1), PEO‐LiCF3SO3([EO]/[Li]= 4), and PEO‐NaI ([EO]/[Na]= 4). The mixed‐salt system was shown to have a larger amorphous phase content than either of the single‐salt systems and more potential charge carriers. A dramatic effect upon the lithium motion and the microviscosity of the amorphous phase was noted upon the mixing of salts. It is proposed that some lithium ions are in environments of low symmetry, possibly of the ion‐pair type, and do not contribute to the n.m.r. signal. The recrystallisation behaviour of the mixed‐salt material was studied by the n.m.r. technique and an initial fast recrystallisation appears to be due to the formation of the high‐meltin

ISSN:0007-1641    

DOI:10.1002/pi.4980200308

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractRadiotracer measurements of the22Na+and S14CN−diffusion coefficients in PEO‐NaSCN (x= 6, 8 and 12) and PPO‐NaSCN (x= 8) are reported, where PEO = poly(ethylene oxide), PPO = poly(propylene oxide), andx= [EO units]/[NaSCN]or [PO units]/[NaSCN]. The results are compared with ionic conductivity measurements on the same samples. Measurements for the PEO samples were taken above the melting point of pure PEO and the results interpreted, particularly for the sample most dilute in salt, in terms of ‘free ions’ as the dominant charge carriers. For PPO the results are less clear, although there is good evidence for the onset of ion aggregation prior to separation of salt at higher tem

ISSN:0007-1641    

DOI:10.1002/pi.4980200309

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe gel‐sectioning technique has been used to measure the radiotracer diffusion coefficients of Na+and SCN−ions in solutions of sodium thiocyanate in tetra(ethylene glycol) dimethyl ether (‘tetraglyme’), a liquid system which can be used as a model polymer electrolyte. Measurements were made at 298 K over the molar concentration range tetraglyme‐NaSCN between 2.5 and 50. At all concentrations the diffusion coefficients of both ions were virtually identical and decreased markedly at high salt concentrations. Comparison of the diffusion results with conductivity measurements on the same samples gives evidence for the aggregation of ions at low salt concentrations (tetraglyme‐NaSCN>20). At higher salt concentrations aggregation does not need to be invoked to explain the results. The implications for other polyether electrolytes ar

ISSN:0007-1641    

DOI:10.1002/pi.4980200310

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe kinetics of lithium metal and of selected intercalation electrodes in electrochemical cells using poly(ethylene oxide)‐based electrolytes are discussed on the basis of cyclic voltammetry, polarisation curves and frequency response analysis. The results indicate that the lithium electrode, even if inherently reversible, may be passivated by the polymer electrolytes with the growth of a resistive layer at the interface. Among the most common intercalation compounds the Li1+xV3O8bronze shows reversible behaviour and appears to be a very promising positive electrode in rechargeable lithium/polymer electrolyte batterie

ISSN:0007-1641    

DOI:10.1002/pi.4980200311

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe stability of evaporated lithium with poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO) and oxyethylene‐oxymethylene copolymer, doped with lithium perchlorate, in ultra‐thin‐film cells, was studied by impedance spectroscopy at room temperature. The formation and growth of a passivating film at the lithium/PEO interface has been observed, under open circuit conditions. The thickness of the passivating layer was estimated by assuming the dielectric constant of the interfacial product. A more extensive interfacial reaction was observed in the case of PPO. A very fast interfacial reaction was observed between lithium and amorphous copo

ISSN:0007-1641    

DOI:10.1002/pi.4980200312

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY