| 1. |
- Gavelin, Patrik, et al.
(författare)
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Amphiphilic solid polymer electrolytes
- 2002
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Ingår i: Solid State Ionics. - 1872-7689 .- 0167-2738. ; 147:3-4, s. 325-332
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Konferensbidrag (refereegranskat)abstract
- Amphiphilic graft copolymers consisting of methacrylate backbones carrying approximately 48 wt.% of ethylene oxide [(EO)(9) or (EO)(23)] side chains as ionophilic groups and fluorocarbon or hydrocarbon side chains as ionophobic groups were prepared. Solid polymer electrolytes based on the copolymers and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) were characterized by DSC and the impedance spectroscopy. A maximum ion conductivity of 8 x 10(-5) S cm(-1) at 60 degreesC was found for a polymer electrolyte based on a copolymer having hydrocarbon side chains and (EO)(23) side chains, despite an EO content of only 50 wt.%. No (EO)(n) side chain crystallinity in the electrolytes was detected by calorimetry. The hydrocarbon side chains, on the other hand, were found to form a crystalline phase in the electrolytes. The melting of this phase was not reflected in the shape of the Arrhenius conductivity plot. This indicated that the segmental mobility in the ion conducting phase did not decrease as a result of the presence of the crystalline hydrocarbon phase.
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| 2. |
- Albinsson, I., et al.
(författare)
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Ion association effects and ionic conduction in polyalkalene modified polydimethylsiloxanes
- 1992
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Ingår i: Solid State Ionics. - : Elsevier. - 0167-2738 .- 1872-7689. ; 53-56:Part 2, s. 1044-1053
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Tidskriftsartikel (refereegranskat)abstract
- Poly (ethylene oxide) and poly (propylene oxide) modified poly (dimethyl siloxane) (PDMS) have been complexed with LiCF3SO3, NaCF3SO3 and KCF3SO3. In order to study ion association in these systems, the nondegenerate symmetric stretch (A1, SO3) Raman modes have been studied as a function of temperature at several different salt concentrations. Ionic conductivity has also been measured. For the poly (ethylene oxide) modified PDMS (PEO-PDMS), ether oxygen to metal ratios ranged from 12500:1 to 9:1. Changing the cation from Li+ to Na+ to K+ increases the conductivity of the complex. Plots of the molar conductivity versus salt concentration show that the characteristic shape and the region of increase in the molar conductivity is influenced most by the fraction of “free” ions which increases with increasing salt concentration. Charged triplets and contact ion-pairs are also present at the higher salt concentrations; the number of triplets increases with concentration and temperature. Non-VTF behaviour is observed. For the poly (propylene oxide) modified PDMS (PPO-PDMS) (with excess PPO), phase separation is observed when these triflate salts are complexed in. These solutions above and below the boundary layer have been studied by Raman spectroscopy revealing that the upper region is siloxane rich. The formation of the boundary layer is attributed to an increasing difference in surface tension between the PPO/salt/PPO-PDMS complexes and the separate PPO, PPO-PDMS components. The boundary layer moves up with increase in salt concentration. There is evidence of “free” ions, contact-ion pairs, triplets and aggregates. Values of conductivity of 2.2×10−6 and 1.6×10−5 S/cm are quoted for 293 K and 8 mol% LiCF3SO3 in respectively PPO-PDMS/PPO and PEO-PDMS/PEO. Both are better conductors than the corresponding 8 mol% PPG4000/LiCF3SO3 complex.
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| 3. |
- Edman, Ludvig, 1967-, et al.
(författare)
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Thermal analysis of a solid polymer electrolyte and a subsequent electrochemical investigation of a lithium polymer battery
- 2003
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Ingår i: Solid State Ionics. - : Elsevier. - 0167-2738 .- 1872-7689. ; 158:1-2, s. 177-186
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Tidskriftsartikel (refereegranskat)abstract
- A notable slow recrystallization process following heating above the liquidus line for P(EO)nLiTFSI electrolytes with n values ranging from 5 to 12 is shown to be correlated to a slow nucleation process as concluded from extensive differential scanning calorimetry (DSC) measurements. This concentration anomaly motivated the assembly of a room temperature Li/P(EO)8LiTFSI/LixMnO2 cell, containing a preheated amorphous electrolyte, which initially delivered a cathode capacity of 27 mAh/g at a current density of 0.1 mA/cm2 and 60 mAh/g at 0.05 mA/cm2 as compared to typical discharge capacities of 95 - 120 mAh/g for similar polymer systems at 85 degreesC and liquid systems at room temperature. The delivered capacity decreased during cell cycling and reached a limiting value of 10 mAh/g after cycle 15. Li/P(EO)nLiTFSl/LixMnO2 cells (n = 6, 8, 20) were also cycled extensively at 85 degreesC, and an analysis of the results indicates that the solid electrolyte interfacial (SEI) resistance, formed between the lithium negative electrode and the electrolyte, remains constant during cycling (RSEI ≈ 3-7 x 10-3 Ωm2) and is of the same magnitude as the bulk electrolyte resistance. Furthermore, it is shown that severe concentration gradients develop over the electrolytes during cell operation, and that the marked diminishing cathode capacity for the n = 8 cell at 20 degreesC, and also for the n = 20 cell at 85 degreesC, with increasing current density, appears to be related to a limiting current situation. Losses in energy and power densities at steady state conditions for n = 6 and n = 8 cells at 85 degreesC appear mainly related to the development of a concentration overpotential, which lowers the working potential curve and causes the cutoff potential to be reached sooner.
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| 4. |
- Furlani, Maurizio, et al.
(författare)
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Time resolved luminescence and vibrational spectroscopic studies on complexes of poly(ethylene oxide) oligomers and EuTFSI3 salt
- 1998
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Ingår i: Solid State Ionics. - : Elsevier. - 0167-2738 .- 1872-7689. ; 113-115:1-2, s. 129-138
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Tidskriftsartikel (refereegranskat)abstract
- AC impedance, FT-Raman/IR, DSC, continuous and time resolved luminescence measurements have been conducted on solutions of poly(ethylene glycol) (PEG), MW 400, and poly(ethylene glycol)-dimethyl ether (DME), MW 425, complexed with Eu[N(CF3SO2)2]3 salt, EuTFSI3. Ion-polymer interactions are manifested as changes in characteristic vibrational modes of the polymer, including CH, and -OH stretching motions at ∼2700-3700 cm-1, and also in cation-induced polymer modes at ∼ 865-910 cm-1. Comparing the vibrational features of the TFSI anion (i.e., both Raman and IR), we find no modes that are substantially changing with increasing salt concentration, or upon change of cation (i.e., M = Li+, Na+ or Eu3+). This observation suggests that TFSI-salts are highly dissociated in PEO oligomer solvents even up to relatively high salt concentrations (i.e., O:M = 26: 1). Clear evidence of -OH end-group coordination in the PEG systems emerges from IR spectra and the strong dependence of T-g upon salt concentration, and also from the pronounced temperature dependence of the ionic conductivity. Despite of this, however, few distinct differences could be observed in the luminescence spectra between the PEG and the DME host materials. Luminescence spectra of Eu3+ show a relatively small distribution of energies (30 cm-1 FWHM in 5D0 - 7F0) in a low-symmetry site throughout the entire concentration range investigated for both PEG and DME solvents. The population decays of the 5D0 excited state, measured by exciting to the degenerate state 5D1 with a pulsed dye laser, are also very similar for the PEG and DME hosts (lifetimes = 0.35 ms).
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| 5. |
- HERMANSSON, KERSTI, et al.
(författare)
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ON THE ROLE OF ELECTRIC-FIELDS FOR PROTON-TRANSFER IN WATER
- 1995
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Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738 .- 1872-7689. ; 77, s. 34-42
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Tidskriftsartikel (refereegranskat)abstract
- The influence of uniform and non-uniform electric fields on one-dimensional proton transfer curves for (H2O)(2), H5O2+ and H3O2- has been examined using quantum-mechanical ab initio calculations. Both liquid-state and solid-state environments are discussed. For the charged complexes the transfer barrier is removed or greatly reduced by a field as small as 0.005 a.u. (2.5 X 10(7) V/cm). Local field fluctuations of this size are easily produced in condensed aqueous systems at room temperature. For the asymmetric single-well potential of an (H2O)(2) complex, a field ten times larger is needed to move the minimum from one side to the other across the O ... O bond. Such local fields can be achieved in ionic aqueous systems. The energy barrier for proton transfer in ice Ih has been computed using a periodic Hartree-Fock approach; the barrier for a fully concerted proton transfer is similar to 60 kJ/mol.
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| 6. |
- Landa, A. I., et al.
(författare)
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Phase stability of Li(Mn100-xCox)O-2 oxides : an ab initio study
- 2002
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Ingår i: Solid State Ionics. - 0167-2738 .- 1872-7689. ; 149:04-mar, s. 209-215
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Tidskriftsartikel (refereegranskat)abstract
- The full charge density exact muffin-tin orbitals method has been used to study the stability of lithium manganese oxides exhibiting different crystallographic forms. Calculations have been performed in various crystallographic phases of LiMnO2 for the ferromagnetic and antiferromagnetic spin configurations on Mn sublattice, as well as for the state with local moment disorder. For the ordered LiMnO2 compound, the experimentally observed antiferromagnetic orthorhombic ground state structure was reproduced. The effect of doping of the Mn sites by Co was considered with the primary aim to predict the stabilization of the layered structure.
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| 7. |
- Lundin, Anders, et al.
(författare)
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Effect of high pressure on volume and ion-ion interaction in poly (propylene glycol) complexed with LiCF3SO3
- 1993
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Ingår i: Solid State Ionics. - : Elsevier. - 0167-2738 .- 1872-7689. ; 60:1-3, s. 43-46
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Tidskriftsartikel (refereegranskat)abstract
- Raman spectroscopy has been used to study the ion-ion interaction in poly(propylene glycol) (PPG) complexed with LiCF3SO3 under pressures up to 0.4 GPa. In addition, measurements of the variation of volume with pressure and salt concentration have been made. The Raman studies revealed increasing solubility and fewer ion pairs in the salt-polymer complex with increasing pressure. The volume dependence of the ion-ion interaction was calculated from the experimental data for relative volume versus pressure.
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| 8. |
- Mattsson, B., et al.
(författare)
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Raman scattering investigations of PEO and PPO sulphonic acids
- 1997
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Ingår i: Solid State Ionics. - : Elsevier. - 0167-2738 .- 1872-7689. ; 97:1-4, s. 309-314
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Tidskriftsartikel (refereegranskat)abstract
- Sulphonic acid derivatives of polyethers, of interest as proton conducting materials, were investigated using Raman spectroscopy, focusing on influence of hydration on ion configuration and polymer conformation. Upon increasing hydration we observe a polarised mode building up at approximately 1040 cm-1, assigned to the symmetric stretching vibration of a completely hydrated SO3- group. The data suggest that the proton-sulphonic groups do not dissociate until the materials are considerably hydrated thus explaining the low proton conductivities found for these materials below a relative humidity of 75%.
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| 9. |
- Torell, Lena M., et al.
(författare)
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The importance of ion-polymer crosslinks in polymer electrolytes
- 1992
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Ingår i: Solid State Ionics. - Amsterdam : Elsevier. - 0167-2738 .- 1872-7689. ; 53-56:Part 2, s. 1037-1043
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Tidskriftsartikel (refereegranskat)abstract
- Raman-, Brillouin-and photon correlation spectroscopy have been used to study LiCF3SO3 and NaCF3SO3 containing polyethers (PEO and PPO). At focus are factors controlling the ion-polymer interactions, the formation of transient ionic crosslinks and their effect on the local flexibility. Brillouin and photon correlation spectroscopy show that the structural relaxation time is independent of the polymeric chain length for chains longer than n≈20 repeat units. For shorter chains OH bridging slightly stiffens the dynamics whereas for CH3 end-capped chains the local chain flexibility increases dramatically as n decreases. The crossover at ∼20 monomer indicates the number of monomers involved in the cooperative segmental rearrangements needed for structural relaxations in high Mw complexes, and thus also for an ionic displacement to occur in these systems. It is found that transient crosslinks are established for n > 4 and they considerably slow down the local dynamics. The density of crosslinks is found to be strongly temperature dependent and this is the reason for departure from Tg scaled dynamics in the complexes.
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| 10. |
- Zhu, Bin, et al.
(författare)
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Chemical stability study of Li2SO4 in a H2S/O-2 fuel cell
- 2000
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Ingår i: Solid State Ionics. - 0167-2738 .- 1872-7689. ; 127:02-jan, s. 83-88
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Tidskriftsartikel (refereegranskat)abstract
- Although H-2/O-2 fuel cells using Li2SO4 as the electrolyte have encountered problems in their chemical instability, the Li2SO4 electrolyte shows an excellent chemical stability under the operation conditions of a fuel cell using H2S as the fuel. Both thermodynamic analysis and experiments have demonstrated that it is feasible to develope practical H2S/O-2 fuel cells and co-generation devices based on the Li2SO4 electrolyte.
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