| 1. |
- Abbrent, Sabina, et al.
(författare)
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Gel electrolytes prepared from oligo(ethylene glycol)dimethacrylate : glass transition, conductivity and Li+-coordination
- 1998
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Ingår i: Electrochimica Acta. - 0013-4686 .- 1873-3859. ; 43:10-11, s. 1185-1191
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Tidskriftsartikel (refereegranskat)abstract
- The influence of two plasticizers, propylene carbonate and dimethyl sulphoxide, as well as different salt concentrations of Li(TFSI), on properties of a polymer gel electrolyte material has been studied using differential scanning calorimetry (DSC) and ac impedance and FTIR spectroscopy. Variations of glass transition temperature and the conductivity behaviours of the systems were examined, and found to be highly dependent on the amount and type of the plasticizer used. Characteristic band-shifts in FTIR spectra, indicating coordination of lithium ions, have been found for the polymer and both the plasticizers in the corresponding binary solutions. These shifts were used to study the coordination preferences in the complete ternary electrolyte system. The combined results from the three experimental techniques have been discussed.
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| 2. |
- Behm, Mårten, et al.
(författare)
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Influence of structure and composition upon performance of tin phosphate based negative electrodes for lithium batteries
- 2002
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Ingår i: Electrochimica Acta. - 0013-4686 .- 1873-3859. ; 47:11, s. 1727-1738
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Tidskriftsartikel (refereegranskat)abstract
- Tin oxide and amorphous tin borophosphates have recently received significant attention as possible new negative electrode materials for lithium batteries. In this study. we have carefully investigated a number of different well-characterised tin phosphates as electrodes in Li-ion cells, in order to better understand the mode of operation of these materials and how their performance is related to structure and composition. The materials that were investigated were crystalline cubic and layered SnP2O7, LiSn2(PO4)(3). Sn2P2O7, and Sn-3(PO4)(2). and amorphous Sn2BPO6. Cubic SnP2O7 showed the best performance with a reversible specific charge capacity of > 360 mA h g(-1) and a capacity retention of 96% over 50 cycles when cycled between 0.02 and 1.2 V versus Li-m. The three Sn(IV) materials showed lower initial reversible capacity but better capacity retention than the three Sn(II) materials in the study. Their higher proportion of inert matrix material can partly explain this. However. cubic SnP2O7 cycled significantly better than its layered polymorph. which shows that the structure of the starting material is also of great importance. Another important conclusion drawn front the results is that it is not necessary for the starting material to be amorphous, or if crystalline, to have small grain size, to cycle well. The three pyrophosphates all show an initial reduction capacity that corresponds to around 2 Li per P2O74- unit more than is predicted by theory. This might be explained by reductive break-up of the P 0 P bond.
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| 3. |
- Bursell, Martin, et al.
(författare)
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La0.6Ca0.4CoO3, La0.1Ca0.9MnO3 and LaNiO3 as bifunctional oxygen electrodes
- 2002
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Ingår i: Electrochimica Acta. - 0013-4686 .- 1873-3859. ; 47:10, s. 1651-1660
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Tidskriftsartikel (refereegranskat)abstract
- A series of perovskite catalysts was investigated for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline electrolyte and at room temperature, supplied by oxygen or air. A meniscus cell was used to screen-test candidate catalysts for their bifunctionality and assess their activity for ORR at 3 mm depth of immersion (DOI) in the electrolyte. Based on the meniscus data LaNiO3, La0.1Ca0.9MnO3 and La0.6Ca0.4CoO3 were selected for further assessment in microelectrode and half-cell studies. Activity tests for the ORR and OER, Tafel slopes at high current densities and apparent activation energies for the ORR were determined using a microelectrode technique on samples of the selected perovskites, La0.1Ca0.9MnO3, La0.6Ca0.4CoO3 and LaNiO3 with and without graphite support. Tafel slopes of ca. 120 mV per decade and apparent activation energies of approximately 18 kcal mol(-1) were measured at high cathodic current densities. Cycle-life and performance of La0.1Ca0.9MnO3, La0.6Ca0.4CoO3 and LaNiO3-based gas-diffusion electrodes in half-cell configurations were tested at a constant current density of 25 mA cm(-2) With subsequent and intermittent polarizations. Similar activities resulted in the ORR, while increased numbers of cycles were observed for the La0.1Ca0.9MnO3-based electrode. Furthermore, electrode material compositions, especially PTFE contents were optimized to conform to the establishment of the three phase interactions of the electrode structure, Transmission Electron microscopy (TEM) and BET-surface area analyses were carried out in order to find out the morphological and surface properties of the perovskite materials.
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| 4. |
- Cornell, Ann, et al.
(författare)
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Ruthenium based DSA in chlorate electrolysis–critical anode potential and reaction kinetics
- 2003
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Ingår i: Electrochimica Acta. - 0013-4686 .- 1873-3859. ; 48:5, s. 473-481
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Tidskriftsartikel (refereegranskat)abstract
- Ruthenium based DSA®s have been investigated in chlorate electrolyte using rotating discs made from commercial electrodes. Measurements of the voltammetric charge, q*, and of iR-corrected polarisation curves up to current densities of 40 kA/m2 were recorded on new anodes and on aged anodes from 3 years of production in a chlorate plant. Anodic polarisation curves in chloride containing electrolytes bend towards a higher slope at approximately 1.2 V versus Ag/AgCl, likely due to oxidation of ruthenium. The potential and current density at which the curves bend have been defined as the critical potential, Ecr, and the critical current density, icr. New anodes that operate at a relatively high potential, >Ecr, obtain an increase in real surface area and thereby a decrease in anode potential and in the selectivity for oxygen formation during the first months of operation. Experiments at constant ionic strength under chlorate process conditions showed that Ecr decreased with increasing chloride concentration with a factor of −0.09 V/log Cl−, whereas icr increased with increasing chloride concentration. The chlorine evolution reaction was of the first order with respect to chloride concentration. A possible reaction mechanism for chlorine formation is suggested.
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| 5. |
- Cornell, Ann, et al.
(författare)
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The effect of addition of chromate on the hydrogen evolution reaction and on iron oxidation in hydroxide and chlorate solutions
- 1992
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Ingår i: Electrochimica Acta. - 0013-4686 .- 1873-3859. ; 37:10, s. 1873-1881
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Tidskriftsartikel (refereegranskat)abstract
- The addition of chromate to the electrolyte has been shown in previous papers to hinder almost completely the electroreduction of hypochlorite, while the hydrogen evolution reaction can still proceed on the cathode surface. The effect of chromate on the latter reaction has been studied with cyclic voltammetry and by measuring polarization curves for iron electrodes in both chlorate and hydroxide electrolyte. For the sake of comparison, the investigations have also included the effects on the gold electrode in hydroxide solution. The results showed that the kinetics is changed in a way that decreases the differences in electrocatalytic activity between different electrode materials. Also, the innermost layer of the chromium hydroxide film seems to be the most active part in the HER. The chromate also affects the oxidation of the iron surface. A practical result of this is that the activity for the HER on corroded iron in chlorate electrolyte depends on whether the electrolyte contained chromate during the period of corrosion. The activation becomes much smaller if chromate is present.
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| 6. |
- Edwards, M. O. M., et al.
(författare)
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'Electric-paint displays' with carbon counter electrodes
- 2001
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Ingår i: Electrochimica Acta. - 0013-4686 .- 1873-3859. ; 46:13-14, s. 2187-2193
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Tidskriftsartikel (refereegranskat)abstract
- 'Electric-paint displays' are electrochromic displays with dyed nanostructured metal-oxide electrodes, e.g. viologen-derivatized nanostructured titanium dioxide electrodes. Such displays are particularly promising for applications with low switch frequency, large segment areas, and high demands on colours, background brightness, and large viewing-angles. The concept is simple and well suited for inexpensive industrial production methods. We present blue-on-white electric-paint displays with porous carbon counter electrodes. The initial results with laboratory prototypes are promising. The switch time is about 1/2 s and the reflectance in the bleached state is as high as 40-55% in the visible region. Furthermore, the display prototypes sustain more than 100 000 switching cycles without severe degradation. The results from spectroelectrochemical measurements on the assembled displays are presented.
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| 7. |
- Ferry, Anders, et al.
(författare)
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A Raman, ac impedance and pfg-NMR investigation of poly(ethylene oxide) dimethyl ether (400) complexed with LiCF3SO3
- 1997
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Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 43:10-11, s. 1471-1476
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Tidskriftsartikel (refereegranskat)abstract
- ac impedance, Raman spectroscopy and pulsed field gradient NMR measurements have been conducted on solutions of poly(ethylene oxide) dimethyl ether of molecular weight 400 complexed with LiCF3SO3, as a function of salt concentration; the ether oxygen to alkali metal cation ratios (O:M) ranging from 53:1 to 563:1. From an analysis of the νs(SO3) band envelope of the triflate anion, the relative concentrations of anions in various chemical environments have been calculated. A slight redissociation effect is observed with increasing salt concentration which correlates well with an observed increase in the molar conductivity. Pulsed field gradient NMR measurements show that the 1H, 7Li and 19F self-diffusion coefficients all decrease monotonically with increasing salt concentration. Experimental conductivity data is compared to values calculated from the diffusion coefficients using the Nernst-Einstein relation. We find that the calculated values are higher for all concentrations; the discrepancy increases with decreasing salt concentration.
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| 8. |
- 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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| 9. |
- 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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| 10. |
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