| 1. |
- Ferry, Anders, et al.
(författare)
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The molar conductivity behavior in polymer electrolytes at low salt concentrations : a raman study of poly(propylene glycol) complexed with LiCF3SO3
- 1995
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Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 40:13-14, s. 2369-2373
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Tidskriftsartikel (refereegranskat)abstract
- Raman scattering measurements have been carried out on poly(propylene glycol) complexed with LiCF3SO3 salt over a wide salt concentration range, the ether oxygen to alkali metal cation ratios (O:M) ranging from 4820:1 to 12:1. The relative concentrations of solvated anions, anion-cation pairs and ionic aggregates have been calculated from an analysis of the symmetric anion stretch. The degree of association is found to be almost constant in the O:M range 4820:1-40:1 whereafter it increases with increasing salt concentration. The results show that the dramatic increase reported for the molar conductivity in the O:M range 1000:1-40:1 cannot be explained by the redissociation of contact ion pairs or the formation of conducting triplets. Instead the major contribution to the conductivity increase seems to be a concentration dependent enhancement of the ionic mobility. A percolation based ionic hopping process involving exchange between ions in pairs and dissolved ions, either free or coordinated to ether oxygen sites, is advanced as a possible microscopic mechanism.
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| 2. |
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| 3. |
- Ferry, Anders, et al.
(författare)
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Transport property measurements of polymer electrolytes
- 1998
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Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 43:10-11, s. 1387-1393
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Tidskriftsartikel (refereegranskat)abstract
- Straightforward electrochemical methods for determining the transport properties (bulk ionic conductivity, salt diffusion coefficient, and cation transference number) of polymer electrolytes are described herein. The new technique for measuring t0+ is:based on concentrated solution theory, and requires no assumptions to be made concerning ideality of the solution. The experimental methods are described and results on representative polymer electrolyte systems are presented in this paper. Cation transference numbers are found to be salt-concentration dependent and considerably less than unity or even negative over a wide concentration range. This implies that the cationic current is mainly carried by complexed ions. The presence of associated ionic species in the present systems is confirmed by Raman spectroscopic evidence. Finally, the practical effects of a negative t0+ on cell operation and implications for device design are discussed.
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| 4. |
- Orädd, Greger, et al.
(författare)
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Diffusion and dielectric studies of the system PPO4000–NH4CF3SO3
- 1999
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Ingår i: International Conference(12th) on Solid State Ionics Held in Kassandra, Halkidiki Thessaloniki, Greece on June 6-12, 1999. ; 136-7, s. 457-61
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Konferensbidrag (refereegranskat)abstract
- A polymer electrolyte system composed of poly(propylene oxide) of molecular weight 4000 (PPO4000) complexed with NH4CF3SO3 (NH4TF) has been investigated by multinuclear pfg-NMR and AC impedance methods. Samples in the concentration range 0.03–0.69 mol/kg (O:NH4 ratios of 500:1–22:1) have been investigated over the temperature range 25–75°C. The combination of AC conductance and pfg-NMR diffusion measurements gives clear evidence that extensive ion-aggregation/clustering occurs at low salt concentrations. With increasing salt-content the Haven ratio, defined as Λcalc/Λexp, decreases from >100 to 2 when going from 0.03 to 0.69 mol/kg. Such gross deviations from the Nernst–Einstein relation (i.e. Λ ∝ D++D−) originate in extensively correlated motions of ions. We interpret the results in terms of labile salt-rich sub-domains being further destabilized through an increase in the dielectric constant of the solution with increasing salt content.
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