| 1. |
- Aguilera Medina, Luis, 1983, et al.
(författare)
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A structural study of LiTFSI-tetraglyme mixtures: From diluted solutions to solvated ionic liquids
- 2015
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Ingår i: Journal of Molecular Liquids. - : Elsevier BV. - 0167-7322. ; 210:Part B, s. 238-242
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Tidskriftsartikel (refereegranskat)abstract
- We report on the nano-structure of solvated ionic liquids (SILs) formed by dissolving a Li-salt (LiTFSI) in the solvent tetraglyme. Using small angle X-ray scattering (SAXS), supported by Raman spectroscopy and computational modeling we follow how the nano-structure develops as Li-salt is added to the solvent. We find that, as the Li-salt concentration is increased a peak at Q 0.95 Å- 1 grows in intensity, signaling the presence of structural correlations typical of those found in traditional ionic liquids. The intensity of the peak reaches its maximum at the equimolar concentration, where each Li-ion can be solvated by one solvent molecule forming an effective cation complex. Combining the SAXS data with computer modeling we show that this peak can be assigned to charge alternation, also found in traditional ionic liquids. However, we also show that even at the equimolar concentration not all Li-ions are solvated by the solvent molecules, but a small fraction interacts directly with the anion (TFSI).
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| 2. |
- Aguilera Medina, Luis, 1983, et al.
(författare)
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Enhanced low-temperature ionic conductivity via different Li+ solvated clusters in organic solvent/ionic liquid mixed electrolytes
- 2016
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 18:36, s. 25458-25464
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Tidskriftsartikel (refereegranskat)abstract
- We investigate Li+ coordination in mixed electrolytes based on ionic liquids (ILs) and organic solvents and its relation with the macroscopic properties such as phase behaviour and ionic conductivity. Using Raman spectroscopy we determine the solvation shell around Li+ in mixtures formed by the IL N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide, the organic solvents ethylene carbonate and dimethyl carbonate (EC : DMC 1 : 1), and the salt LiTFSI. We find that the organic solvent molecules preferentially solvate Li+ as long as there are enough of them. Our results are consistent with a model where Li(EC)(3)(DMC)(1) and Li(EC)(2)(DMC)(2) are the main complexes formed by the organic solvent molecules and where TFSI- mainly participates in Li(TFSI)(2)(-) clusters. As the amount of organic solvent is increased, the number of TFSI- around Li+ rapidly decreases showing a higher affinity of the organic solvents to solvate Li+. The changes in the local configurations are also reflected in the ionic conductivity and the phase behaviour. The formation of larger clusters leads to a decrease in the conductivity, whereas the presence of several different clusters at intermediate compositions effectively hinders crystallization at low temperatures. The result is an enhanced low-temperature ionic conductivity in comparison with the pure IL or organic solvent electrolytes.
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| 3. |
- Kim, Jae-Kwang, 1978, et al.
(författare)
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Characterization of N-butyl-N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide-based polymer electrolytes for high safety lithium batteries
- 2013
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 224:15 Feb. 2013, s. 93-98
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Tidskriftsartikel (refereegranskat)abstract
- Poly(vinylidene difluoride-co-hexafluoropropylene) (PVdF-HFP) membrane was prepared by electrospinning. The membranes served as host matrices for the preparation of ionic liquid-based polymer electrolytes (ILPEs) by activation with non-volatile, highly thermally stable, and safe room temperature ionic liquid (RTIL) electrolytes; N-butyl-N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide (Py14TFSI) complexed with 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). In this work, the first combination of electrospun PVdF-HFP fiber polymer host and pyrrolidinium-based ionic electrolyte was employed for highly stable lithium batteries. The ILPE exhibited low Li+-TFSI coordination, low crystallinity, high thermal stability, high electrochemical stability, and high ionic conductivity with a maximum of 1.1 x 10(-4) S cm(-1) at 0 degrees C. The ILPE exhibited good compatibility with a LiFePO4 electrode on storage and good charge-discharge performance in Li/ILPE/LiFePO4!
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| 4. |
- Kim, Jae-Kwang, 1978, et al.
(författare)
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Nano-fibrous polymer films for organic rechargeable batteries
- 2013
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 1:7, s. 2426-2430
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Tidskriftsartikel (refereegranskat)abstract
- We propose a nano-fibrous polymer (NFP) film, fabricated by electrospinning poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA), as a key component in high performance organic batteries. The new strategy with a NFP film enables extraordinary rate capability and excellent cyclability, due to its special morphology. Moreover, the NFP film enhances the flexibility of the electrode at a low cost and prevents dissolution of PTMA into the electrolyte.
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| 5. |
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| 6. |
- Kim, Jae-Kwang, 1978, et al.
(författare)
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Towards flexible secondary lithium batteries: polypyrrole-LiFePO4 thin electrodes with polymer electrolytes
- 2012
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 1364-5501 .- 0959-9428. ; 22:30, s. 15045-15049
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Tidskriftsartikel (refereegranskat)abstract
- A thin flexible polypyrrole-lithium iron phosphate (PPy-LiFePO4) based cathode has been fabricated. A slurry containing carbon black, a binder and the active material prepared by direct polymerization of pyrrole on the surface of LiFePO4 (LFP) was spread on an Al/carbon film substrate by the doctor blade method. Transmission electron micrographs reveal that PPy nanoparticles form a web like structure over the surface of LFP particles. After doping with lithium ions the PPy network becomes conducting. When evaluated as a cathode of 180 mu m thickness together with a gel polymer electrolyte and a lithium anode, the charge-discharge performance reveals that the electrochemical properties of LFP are influenced to a considerable extent by the PPy. The cells show high initial discharge capacities of 135 and 110 mA h g(-1) for 0.041 (C/10) and 0.21 (C/2) mA cm(-2), respectively, and high active material utilization. Furthermore the cells exhibit stable cycle properties even at 0.21 mA cm(-2) with a low capacity fade per cycle (similar to 0.3%).
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| 7. |
- Pitawala, Jagath, 1976, et al.
(författare)
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Physical Properties, Ion-Ion Interactions, and Conformational States of Ionic Liquids with Alkyl-Phosphonate Anions
- 2013
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 117:27, s. 8172-8179
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the ionic conductivities, phase behaviors, conformational states, and interactions of three ionic liquids based on imidazolium cations and phosphonate anions with varying alkyl chain lengths. All three ionic liquids show high conductivities, with 1,3-dimethylimidazolium methyl-phosphonate [DiMIm(MeO)(H)- PO2] being the most conductive (7.3 x 10(-3) S cm(-1) at 298 K). The high ionic conductivities are a result of the low glass-transition temperatures, T-g, which do not change significantly upon changing the cation and/or anion size. However, there is a slight dependence of the temperature behavior of the conductivity on the size of the ions, as seen from the fragility parameter (D) obtained from fits, to the Vogel-Fulcher-Tammann equation. The molecular-level structure and interactions of the phosphonate anions were examined by Raman spectroscopy and first-principles calculations: The calculations identify two stable conformations for the methyl- and ethyl-phosphonate anions by rotation of the methyl and ethyl groups, respectively. The broad Raman signatures of the anions suggest the coexistence of anion conformers in the ionic liquids and non-negligible cation-anion interactions, with a dependence the position and shape of the bands of the cation species and the alkyl group of the anion.
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| 8. |
- Scheers, Johan, 1979, et al.
(författare)
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Ionic liquids and oligomer electrolytes based on the B(CN)(4)(-) anion; ion association, physical and electrochemical propertiesw
- 2011
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 13:33, s. 14953-14959
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Tidskriftsartikel (refereegranskat)abstract
- The role of B(CN)(4)(-) (Bison) as a component of battery electrolytes is addressed by investigating the ionic conductivity and phase behaviour of ionic liquids (ILs), ion association mechanisms, and the electrochemical stability and cycling properties of LiBison based electrochemical cells. For C(4)mpyrBison and C(2)mimBison ILs, and mixtures thereof, high ionic conductivities (3.4
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| 9. |
- Xiong, Shizhao, 1985, et al.
(författare)
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Role of organic solvent addition to ionic liquid electrolytes for lithium–sulphur batteries
- 2015
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069.
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the role of the addition of an organic solvent to an ionic liquid electrolyte for the performance of lithium–sulphur (Li–S) batteries. We find that with a mixed electrolyte, formed by adding 10 wt% 1,3-dioxolane (DIOX) to an ionic liquid, the capacity of a Li–S cell is more than doubled, the rate capability and the cycling performance considerably improved, compared to a cell utilizing a neat ionic liquid electrolyte. The improved performance can be correlated with an enhanced ion transport, evidenced by an increased ionic conductivity and higher limiting current density, directly related to a decrease in viscosity and glass transition temperature of the mixed electrolytes. We show that this in turn is linked to a change in the local environment of the Li-ions where the organic solvent is incorporated in the coordination shell. In addition we show that the mixed electrolytes have a considerably higher thermal stability, in particular a dramatically increased flash point, and improved low temperature properties with respect to a conventional organic solvent based electrolyte currently used for Li–S batteries.
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