| 1. |
- Engström, Niklas, 1985, et al.
(författare)
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Towards Celiac-safe foods: Decreasing the affinity of transglutaminase 2 for gliadin by addition of ascorbyl palmitate and ZnCl2 as detoxifiers
- 2017
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 7:77
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Tidskriftsartikel (refereegranskat)abstract
- Initiation of celiac disease is triggered in the gastrointestinal tract by transglutaminase 2 (TG2) assisted deamidation of gluten peptides. Deamidation is a side-reaction to transamidation and occurs if primary amines are absent. In contrast to deamidation, transamidation does not trigger an immune response. The aim of the study was to identify a suitable food additive that interacts with TG2 binding motives in gluten-derived peptides to prevent deamidation/transamidation. Homology modelling of alpha 2-gliadin and computational screening of compounds for their binding affinity to a common TG2 binding motive (P) QLP were done by using computational approaches followed by experimental testing of TG2 activity. A database containing 1174 potential food grade ligands was screened against the model of alpha 2-gliadin (27 out of 33 aa). Out of the five best ligands, ascorbyl palmitate, was observed to decrease TG2 transamidation of gliadin by 82% +/- 2%. To completely silence the transamidation, we added zinc chloride (ZnCl2), and thereby reached a 99% +/- 1% inhibition of TG2 activity. In addition, we conducted a pilot experiment in which ascorbyl palmitate was observed to decrease TG2 deamidation of gliadin completely. We propose ascorbyl palmitate in combination with ZnCl2 with the future perspective to become an additive in celiac-safe foods.
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| 2. |
- 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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| 3. |
- 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
-
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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| 4. |
- Böhme, Solveig, et al.
(författare)
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Lithium-ion batteries based on SnO2 electrodes and a LiTFSI-Pip14TFSI ionic liquid electrolyte
- 2017
-
Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 1945-7111 .- 0013-4651. ; 164:4, s. A701-A708
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Tidskriftsartikel (refereegranskat)abstract
- The performance of lithium-ion batteries (LIBs) comprising SnO2 electrodes and an ionic liquid (IL) based electrolyte, i.e., 0.5 M LiTFSI in Pip14TFSI, has been studied at room temperature (i.e., 22°C) and 80°C. While the high viscosity and low conductivity of the electrolyte resulted in high overpotentials and low capacities at room temperature, the SnO2 performance at 80°C was found to be analogous to that seen at room temperature using a standard LP40 electrolyte (i.e., 1 M LiPF6 dissolved in 1:1 ethylene carbonate and diethyl carbonate). Significant reduction of the IL was, however, found at 80°C, which resulted in low coulombic efficiencies during the first 20 cycles, most likely due to a growing SEI layer and the formation of soluble IL reduction products. X-ray photoelectron spectroscopy studies of the cycled SnO2 electrodes indicated the presence of an at least 10 nm thick solid electrolyte interphase (SEI) layer composed of inorganic components such as lithium fluoride, sulfates, and nitrides as well as organic species containing C-H, C-F and C-N bonds.
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| 5. |
- Hannauer, J., et al.
(författare)
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The Quest for Polysulfides in Lithium-Sulfur Battery Electrolytes: An Operando Confocal Raman Spectroscopy Study
- 2015
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Ingår i: ChemPhysChem. - : Wiley. - 1439-7641 .- 1439-4235. ; 16:13, s. 2755-2759
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Tidskriftsartikel (refereegranskat)abstract
- Confocal Raman spectra of a lithium-sulfur battery electrolyte are recorded operando in a depth-of-discharge resolved manner for an electrochemical cell with a realistic electrolyte/sulfur loading ratio. The evolution of various possible polysulfides is unambiguously identified by combining Raman spectroscopy data with DFT simulations.
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| 6. |
- Hellberg, Lars, 1960, et al.
(författare)
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Master students learning TRIZ at the University: past experiences, future plans, and best practices
- 2016
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Ingår i: 12th MATRIZ TRIZfest-2016 International Conference, July 28-30, Beijing, People’s Republic of China. - 2374-2275. - 9780692524183
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Konferensbidrag (refereegranskat)abstract
- Creating an efficient learning environment for TRIZ at a university is far from trivial. Although the TRIZ-tools for solving problems can appear simple at a glance, applying them to real world problems by beginners is not. In this paper we share our experiences teaching and developing a university course in TRIZ for Master students with different Engineering backgrounds. The syllabus of the course is presented, student results and feedback are analyzed, and plans for future course development are discussed.
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| 7. |
- Kerner, Manfred, 1984, et al.
(författare)
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Ionic liquid based lithium battery electrolytes: fundamental benefits of utilising both TFSI and FSI anions?
- 2015
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 17:29, s. 19569-19581
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Tidskriftsartikel (refereegranskat)abstract
- Several IL based electrolytes with an imidazolium cation (EMI) have been investigated trying to elucidate a possible beneficial effect of mixing FSI and TFSI anions in terms of physico-chemical properties and especially Li+ solvation. All electrolytes were evaluated in terms of phase transitions, densities and viscosities, thermal stabilities, ionic conductivities and local structure, i.e. charge carriers. The electrolytes with up to 20% of Li-salts showed to be promising for high temperature lithium ion battery application (ca. 100°C) and a synergetic effect of having mixed anions is discernible with the LiTFSI0.2EMIFSI0.8 electrolyte giving the best overall performance. The determination of the charge carriers revealed the SN to be ca. 2 for all analysed electrolytes, and proved the analysis of the mixed anion electrolytes to be challenging and inherently leads to an ambiguous picture of the Li+ solvation.
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| 8. |
- Kerner, Manfred, 1984, et al.
(författare)
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Thermal stability and decomposition of lithium bis(fluorosulfonyl)imide (LiFSI) salts
- 2016
-
Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 6:28, s. 23327-23334
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Tidskriftsartikel (refereegranskat)abstract
- The demand for lithium-ion battery (LIB) electrolytes with improved thermal stabilities, and maintained high ionic conductivities and electrochemical stabilities, has been the driving force behind the use of the lithium bis(fluorosulfonyl)imide (LiFSI) salt as a possible replacement for LiPF6. However, contradictory results have questioned its promising thermal stability and noncorrosive properties. Here the performance of three commercial LiFSI salts is compared with the focus on thermal stability and phase transitions together with a vibrational spectroscopy based assessment of the salt purity and decomposition products. The salts are found to differ significantly in their thermal stabilities as determined by both dynamic and isothermal TGA. In contrast, the FT-IR spectra of the salts are almost identical, while several additional bands are identified in the Raman spectra of the least stable salt. The latter allows for a discussion of the origin and role of salt impurities for the observed thermal (in-)stability. Overall the three salts show differences, but these differences are not straightforward to couple to any changes in the performance of Li/LiFePO4 cells using electrolytes based on these salts, but may nevertheless have implications on battery life-length and for application in various other battery technologies.
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| 9. |
- Kerner, Manfred, 1984, et al.
(författare)
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Towards more thermally stable Li-ion battery electrolytes with salts and solvents sharing nitrile functionality
- 2016
-
Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 332, s. 204-212
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Tidskriftsartikel (refereegranskat)abstract
- The overall safety of Li-ion batteries is compromised by the state-of-the-art electrolytes; the thermally unstable lithium salt, lithium hexafluorophosphate (LiPF6), and flammable carbonate solvent mixtures. The problem is best addressed by new electrolyte compositions with thermally robust salts in low flammability solvents. In this work we introduce electrolytes with either of two lithium nitrile salts, lithium 4,5-dicyano-1,2,3-triazolate (LiDCTA) or lithium 4,5-dicyano-2-trifluoromethylimidazolide (LiTDI), in solvent mixtures with high flashpoint adiponitrile (ADN), as the main component. With sulfolane (SL) and ethylene carbonate (EC) as co-solvents the liquid temperature range of the electrolytes are extended to lower temperatures without lowering the flashpoint, but at the expense of high viscosities and moderate ionic conductivities. The anodic stabilities of the electrolytes are sufficient for LiFePO4 cathodes and can be charged/discharged for 20 cycles in Li/LiFePO4 cells with coulombic efficiencies exceeding 99% at best. The excellent thermal stabilities of the electrolytes with the solvent combination ADN:SL are promising for future electrochemical investigations at elevated temperatures (> 60 degrees C) to compensate the moderate transport properties and rate capability. The electrolytes with EC as a co-solvent, however, release CO2 by decomposition of EC in presence of a lithium salt, which potentially makes EC unsuitable for any application targeting higher operating temperatures.
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| 10. |
- Kim, Jae-Kwang, 1978, et al.
(författare)
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A layer-built rechargeable lithium ribbon-type battery for high energy density textile battery applications
- 2014
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 2:6, s. 1774-1780
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Tidskriftsartikel (refereegranskat)abstract
- We designed a novel layer-built rechargeable lithium ribbon-type battery intended for textile or cloth based applications. The ribbon-type battery, 2.4 mm (or 1 mm) wide and 10 cm long, is composed of a double layer LiFePO4 cathode and an amorphous silicon nanofilm. The double layer LiFePO4 and amorphous silicon electrodes were prepared using the doctor blade method and a vertical deposition technique, respectively. The structure and morphology of the LiFePO4 and the silicon thin film were characterized by Rietveld refinement, SEM and TEM. At room temperature the ribbon-type battery exhibited an initial discharge capacity of 166.4 and 132.7 mA h g (1) at 0.5 and 1 C-rate, respectively. A reasonably good cycling performance and high coulombic efficiency under the high current density of 1 C-rate could be obtained with the Si/LiFePO4 ribbon-type battery. Also, a high volumetric capacity of 336 mA h cm (3) at 0.5 C-rate was achieved, which makes the ribbon-type battery suitable for practical use.
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| 11. |
- 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
-
Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 224:15 Feb. 2013, s. 93-98
-
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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| 12. |
- Kim, Jae-Kwang, 1978, et al.
(författare)
-
Facile preparation of nanoporous and nanocrystalline LiFePO4 with excellent electrochemical properties
- 2013
-
Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 3:43, s. 20836-20842
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Tidskriftsartikel (refereegranskat)abstract
- A modified sol-gel process for the preparation of a nanoporous LiFePO4 (LFP) cathode with a well-ordered carbon coating has been developed. The interconnected nanocrystalline LFP was fabricated by addition of sucrose at certain time intervals, which wraps the pore wall. The atomic structure of the LFP was investigated by Rietveld refinement. The surface structure and pore properties have been investigated by SEM, TEM and BET. The structure of the coated residual carbon on the LFP was analyzed by Raman spectroscopy. Lithium ion diffusion and interface properties of the LFP electrodes were investigated by CV and impedance measurements. The LFP displays a good crystal structure, high reversible capacity, good cycle stability, and high energy efficiency. It also shows excellent high rate capability with a 10 C rate capacity of up to 118.5 mA h g(-1) at the 100th cycle and a high tap density of 1.8 g cm(-3) as a cathode material.
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| 13. |
- Kim, Jae-Kwang, 1978, et al.
(författare)
-
Nano-fibrous polymer films for organic rechargeable batteries
- 2013
-
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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| 14. |
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| 15. |
- Kim, Jae-Kwang, 1978, et al.
(författare)
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Role of lithium precursor in the structure and electrochemical performance of LiFePO4
- 2013
-
Ingår i: Scripta Materialia. - : Elsevier BV. - 1359-6462. ; 69:10, s. 716-719
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Tidskriftsartikel (refereegranskat)abstract
- This study highlights the importance of precursor selection. Although a great understanding of the materials properties of LiFePO4 has been achieved, the role of the lithium precursor has been almost ignored. The lithium precursor used for synthesis of LiFePO4 influences the structure, particle size and electrochemical properties. A lithium precursor dependent structural change of LiFePO4 was observed from Rietveld refinement; using Li2CO3 instead of LiOH as lithium precursor resulted in a smaller crystal size and improved electrochemical properties.
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| 16. |
- Kim, Jae-Kwang, 1978, et al.
(författare)
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Superior Ion-Conducting Hybrid Solid Electrolyte for All-Solid-State Batteries
- 2015
-
Ingår i: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 8:4, s. 636-641
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Tidskriftsartikel (refereegranskat)abstract
- Herein, we developed a high-performance lithium ion conducting hybrid solid electrolyte, consisted of LiTFSI salt, Py14TFSI ionic liquid, and TiO2 nanoparticles. The hybrid solid electrolyte prepared by a facile method had high room temperature ionic conductivity, excellent thermal stability and low interface resistance with good contact. In addition, the lithium transference number was highly increased by the scavenger effect of TiO2 nanoparticles. With the hybrid solid electrolyte, the pouch-type solid-state battery exhibited high initial discharge capacity of 150mAhg(-1) at room temperature, and even at 1C, the reversible capacity was as high as 106mAhg(-1).
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| 17. |
- 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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| 18. |
- Lundgren, Henrik, et al.
(författare)
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Characterization of the Mass-Transport Phenomena in a Superconcentrated LiTFSI : Acetonitrile Electrolyte
- 2015
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 162:7, s. A1334-A1340
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Tidskriftsartikel (refereegranskat)abstract
- Superconcentration of aprotic electrolytes has recently emerged as a way to stabilize solvents that otherwise would be impossible to use, in e.g. lithium-ion batteries (LIBs). As demanding applications, such as hybrid electric vehicles and fast charging, become increasingly important, battery manufacturers are struggling to find a suitable electrolyte able to deliver high power with low polarization. Electrolyte characterizations able to accurately predict the high-power performance of such electrolytes are also of utmost importance. This study reports a full.characterization of the mass-transport phenomena for a superconcentrated LiTFSL-acetonitrile electrolyte in concentrations ranging from 2.7 M to 4.2 M. The method obtains the ionic conductivity, cationic transport number, diffusion coefficient, and the thermodynamic enhancement factor, by combining mathematical modeling and three electrochemical experiments. Furthermore, the density and the viscosity were measured. The transport number with respect to the room is found to be very high compared to other liquid LIB electrolytes, but a low diffusion coefficient lowers overall performance. The ionic conductivity decreases quickly with concentration, dropping from 12.7 mS/cm at 2.7 M to 0.76 mS/cm at 4.2 M. Considering all the effects in terms of the mass-transport of the electrolyte, the lower end of the studied concentration range is favorable.
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| 19. |
- 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
-
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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| 20. |
- Scheers, Johan, 1979, et al.
(författare)
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A review of electrolytes for lithium-sulphur batteries
- 2014
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 255, s. 204-218
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Forskningsöversikt (refereegranskat)abstract
- To optimize the electrolyte is one of the most important directions to take in order to improve the Li/S battery in terms of performance - especially cell cyclability, rate capability, safety, and life-span. In this review we examine the state of the art for different choices of electrolytes; concepts, design, and materials, and how the resulting chemical and physical properties of the electrolyte affect the overall Li/S battery performance. The objective is to create an overall assessment of electrolytes in use at present and to provide a thorough basis for rational selection of future electrolytes for Li/S batteries.
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| 21. |
- Scheers, Johan, 1979, et al.
(författare)
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All fluorine-free lithium battery electrolytes Dedications: In memoriam of Prof. per Jacobsson.
- 2014
-
Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 251, s. 451-458
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Tidskriftsartikel (refereegranskat)abstract
- Fluorine-free lithium battery electrolytes have been prepared from lithium salts with nitrile based anions, LiB(CN)4 or LiDCTA, dissolved in PEGDME or PC. After soaked into electrospun PAN membranes the resulting electrolytes were tested for physical and electrochemical properties and compared with reference PAN electrolytes containing LiPF6 or LiTFSI. The fluorine-free electrolytes were successfully cycled in Li/LiFePO4 cells at room temperature with up to 98% Coulombic efficiency. Small and qualitatively different effects were observed with the addition of Al 2O3 particles to the PAN membranes, which could be of importance for long-term performance. However, for fluorine-free electrolytes to be truly competitive, the relatively low anodic stability and elevated temperature performance must first of all be improved by a change of solvent - or addition of co-solvents. Further work in this direction is encouraged by the strong influence of the solvent (PC or PEGDME) on the properties of the LiDCTA electrolytes demonstrated in this work. © 2013 Elsevier B.V. All rights reserved.
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| 22. |
- Scheers, Johan, 1979, et al.
(författare)
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Anion-Additive Interactions Studied by Ab Initio Calculations and Raman Spectroscopy.
- 2009
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 1945-7111 .- 0013-4651. ; 156:4, s. A305-A308
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Tidskriftsartikel (refereegranskat)abstract
- The ability of the caLi x (6)pyrrole (C6P) additive to form complexes with several anions is addressed. Ab initio calculations and Raman spectroscopy are used in combination to evaluate the coordination preferences of C6P in the gas phase and to probe the existence of C6P-anion complexes in solution. Favorable reaction energies are calculated for the formation of 1:1 coordination complexes from the isolated species, with the following anion preference: BF 4 - AsF 6 - > ClO 4 - ≈CF 3 SO 3 - > PF 6 - > I - . In connection with available macroscopic data, the calculated results support the assumption of anion coordination by C6P as a mechanism for lithium transference number enhancement. Upon anion coordination to the additive, calculated vibrational spectra show large differences in the N-H stretching region (∼3400 cm -1 ). However, at lower wavenumbers (
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| 23. |
- Scheers, Johan, 1979
(författare)
-
Anions and Additives for Lithium Battery Electrolytes
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Based on the atomic postulate, which is now more than 2400 years old, scientists have developed very advanced tools for studying the material world. With the potential realized with modern computers, more and more sophisticated methods are available for predicting real material properties, even from simple theoretical model systems. Often these predictions are made in conjunction with practical experiments, to assist in the interpretation of experimental data.In this thesis work, a combination of experimental and computational techniques has been applied to study individual components of lithium battery electrolytes. More specifically molecular interactions between anions, and either lithium ions or neutral additives, have been explored by Raman spectroscopy and ab initio computations. With the main aim to predict new suitable anions for lithium salts that will improve the properties of future lithium batteries. In the first of three papers a pure computational study predicts the electrochemical stability and lithium ion pair dissociation energies of two closely related families of heterocyclic anions. Small structural modifications are made by varying the degree and positions of substituent groups; modifications that turn out to have a large effect on the investigated properties. In the second paper a similar approach is taken, but here a single anion is in focus. Properties of this anion and its lithium ion pairs are predicted by computations, while spectroscopic investigations are made of a novel ionic liquid comprising the same anion.In the third and final paper the scientific work of this thesis is concluded with a combined experimental and computational study. The role of a neutral molecular additive in solid polymer electrolytes is explored; an additive designed to improve lithium ion conductivity by trapping anionic species. The anion preferences of the additive are predicted and experimental signs of anion-additive interactions are searched for.
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| 24. |
- Scheers, Johan, 1979, et al.
(författare)
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Anions for lithium battery electrolytes: A spectroscopic and theoretical study of the B(CN)4- anion of the ionic liquid C2mim[B(CN)4]
- 2008
-
Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 1945-7111 .- 0013-4651. ; 155:9, s. A628-A634
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Tidskriftsartikel (refereegranskat)abstract
- On the basis of computations, the B(CN)4 - (bison) anion is shown to be of interest as a fluorine-free alternative in lithium-conducting electrolytes. Compared to PF6 - the bison anion has an equally high stability toward oxidation, while at the same time offering a large reduction of the lithium-ion pair dissociation energy. The bison anion is readily available in a number of ambient-temperature ionic liquids (ILs). In this work, the Raman spectrum of the IL C2mim [B(CN)4] reveals an almost unperturbed bison anion and, consequently, the effects of the anion on the Raman shifts of C2mim + are also very small. © 2008 The Electrochemical Society.
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| 25. |
- Scheers, Johan, 1979, et al.
(författare)
-
Benzimidazole and imidazole lithium salts for battery electrolytes
- 2010
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 195:18, s. 6081-6087
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Konferensbidrag (refereegranskat)abstract
- The intrinsic anion oxidation potential (Delta E-v) and lithium ion pair dissociation energy (Delta E-d) are two important properties for predicting the potential use of new lithium salts for battery electrolytes. In this work several cyano substituted fluoroalkylated benzimidazole and imidazole anions have been investigated computationally to obtain Delta E-v and Delta E-d. Varying the number and position of cyano substituents results in large effects on the electrochemical stability of the anion and on the possible lithium ion pair configurations. The lengthening of the fluoroalkyl group introduces several new stable ion pair configurations and a small increase in anion oxidation stability. The most promising fluoroalkylated anions in the present work are the 4,5,6,7-tetracyano-2-fluoroalkylated benzimidazolides (TTB and PTB), with oxidation potentials suitable for high voltage Li-ion battery applications (
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| 26. |
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| 27. |
- Scheers, Johan, 1979, et al.
(författare)
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Ion-ion and ion-solvent interactions in lithium imidazolide electrolytes studied by Raman spectroscopy and DFT models
- 2011
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 13:23, s. 11136-11147
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Tidskriftsartikel (refereegranskat)abstract
- Molecular level interactions are of crucial importance for the transport properties and overall performance of ion conducting electrolytes. In this work we explore ion-ion and ion-solvent interactions in liquid and solid polymer electrolytes of lithium 4,5-dicyano-(2-trifluoromethyl)imidazolide (LiTDI)-a promising salt for lithium battery applications-using Raman spectroscopy and density functional theory calculations. High concentrations of ion associates are found in LiTDI: acetonitrile electrolytes, the vibrational signatures of which are transferable to PEO-based LiTDI electrolytes. The origins of the spectroscopic changes are interpreted by comparing experimental spectra with simulated Raman spectra of model structures. Simple ion pair models in vacuum identify the imidazole nitrogen atom of the TDI anion to be the most important coordination site for Li+, however, including implicit or explicit solvent effects lead to qualitative changes in the coordination geometry and improved correlation of experimental and simulated Raman spectra. To model larger aggregates, solvent effects are found to be crucial, and we finally suggest possible triplet and dimer ionic structures in the investigated electrolytes. In addition, the effects of introducing water into the electrolytes-via a hydrate form of LiTDI-are discussed.
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| 28. |
- 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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| 29. |
- Scheers, Johan, 1979, et al.
(författare)
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Life of superoxide in aprotic Li-O-2 battery electrolytes: simulated solvent and counter-ion effects
- 2016
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 18:15, s. 9961-9968
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Tidskriftsartikel (refereegranskat)abstract
- Li-air batteries ideally make use of oxygen from the atmosphere and metallic lithium to reversibly drive the reaction 2Li + O-2 Li2O2. Conceptually, energy throughput is high and material use is efficient, but practically many material challenges still remain. It is of particular interest to control the electrolyte environment of superoxide (O-2(star-)) to promote or hinder specific reaction mechanisms. By combining density functional theory based molecular dynamics (DFT-MD) and DFT simulations we probe the bond length and the electronic properties of O-2(star-) in three aprotic solvents -in the presence of Li+ or the much larger cation alternative tetrabutylammonium (TBA(+)). Contact ion pairs, LiO2 star, are favoured over solvent-separated ion pairs in all solvents, but particularly in low permittivity dimethoxyethane (DME), which makes O-2(star-) more prone to further reduction. The Li+-O-2(star-) interactions are dampened in dimethyl sulfoxide (DMSO), in relation to those in DME and propylene carbonate (PC), which is reflected by smaller changes in the electronic properties of O-2(star-) in DMSO. The additive TBA+ offers an alternative, more weakly interacting partner to O-2(star-), which makes it easier to remove the unpaired electron and oxidation more feasible. In DMSO, TBA(+) has close to no effect on O-2(star-), which behaves as if no cation is present. This is contrasted by a much stronger influence of TBA(+) on O-2(star-) in DME -comparable to that of Li+ in DMSO. An important future goal is to compare and rank the effects of different additives beyond TBA(+). Here, the results of DFT calculations for small-sized cluster models are in qualitative agreement with those of the DFT-MD simulations, which suggests the cluster approach to be a cost-effective alternative to the DFT-MD simulations for a more extensive comparison of additive effects in future studies.
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| 30. |
- Scheers, Johan, 1979
(författare)
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New anions for lithium battery electrolytes
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Energy storage is crucial to realize a new global energy paradigm based on renewable energy sources. Batteries are well suited this need, with the advantages of being mobile and potentially environmentally benign. Li-ion batteries have revolutionized the market of portable electronics and are now being implemented as back up electricity for grid storage, and for transportation – powering hybrid and electric vehicles. However, for large scale applications, the safety of current Li-ion batteries is an obstacle. The safety problems of the Li-ion cell is inherent the reactivity of the choice of materials. Of particular concern, is the flammable organic electrolyte with the thermally unstable lithium hexafluorophosphate (LiPF6) salt. New salt alternatives must, in addition to high thermal stability, combine high electrochemical stability with facile Li+ transport.In this thesis, alternatives to LiPF6 are explored by a combination of computational and spectroscopic techniques. The vertical transition energy, ΔEv, and ion pair dissociation energy, Ed, are computational approaches to the electrochemical stability of anions and the Li+–anion interaction strength, respectively. From computationally predicted structures of anions and ion pair configurations, simulated vibration spectra can be compared with experimental Raman spectroscopic results to probe the molecular level environment of electrolytes. The lithium salts investigated can be categorized according to 1) their approximate geometric characteristics; linear, planar, or spherical, and 2) their substituents; –F, –CF3, or –C≡N groups.The approach taken here is extremely idealized compared to the complex nature of real battery electrolytes; this is both a weakness and a strength. It will be further evaluated and modified based on future experimental results – implementation in lithium battery electrolytes.
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| 31. |
- Scheers, Johan, 1979, et al.
(författare)
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Novel Lithium Imides; Effects of -F, -CF(3), and -C N Substituents on Lithium Battery Salt Stability and Dissociation
- 2012
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Ingår i: Electrochemistry. - : The Electrochemical Society of Japan. - 1344-3542 .- 2186-2451. ; 80:1, s. 18-25
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Tidskriftsartikel (refereegranskat)abstract
- New lithium imide salts have been studied using computational chemistry methods. Intrinsic anion oxidation potentials and ion pair dissociation energies are presented for six lithium sulfonyl imides (R-O(2)S-N-SO(2)-R) and six lithium phosphoryl imides (R(2)-OP-N-PO-R(2)), as a function of -F, -CF(3), and -C N substitution. The modelled properties are used to estimate the electrochemical oxidation stability of the anions and the relative ease of charge carrier creation in lithium battery electrolytes. The results show that both properties are improved with cyano-substitution, which in part is corroborated when comparing with other classes of lithium salts. However, the comparison also shows ambiguous oxidation stability results for cyano-substituted reference salts of the type PF(x)(CN)((6) over bar -x) and BF(x)(CN)((4) over bar -x), using two different approaches - we present a tentative explanation for this. For the imide anions and PF(6)(-), the bond dissociation energy is introduced as a third property, to gauge the thermal stability of the imide anions. The results suggest that the C-S and C-P bonds are the most liable to break and that the thermal stability is inversely related to the ion pair dissociation energy. (C) The Electrochemical Society of Japan, All rights reserved.
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| 32. |
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| 33. |
- Scheers, Johan, 1979, et al.
(författare)
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To Break or not to break: Mechanisms of DMSO decomposition in aprotic LiO2 battery electrolytes
- 2016
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Ingår i: 33rd Annual International Battery Seminar and Exhibit: Advanced Battery Technologies for Consumer, Automotive and Military Applications. ; 2016
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Konferensbidrag (refereegranskat)abstract
- Aprotic Li-O2 batteries offer an appealing opportunity to make use of our immediate environment; harvesting the air for oxygen and further reducing and combining it with Li+ to form LiO2 or Li2O2 at the cathode/electrolyte interface. Although the electrochemistry of such a device could in principle be operated reversibly, side-reactions interfere with the main reactions and limit the lifetime of practical Li-O2 cells – so far operated only in pure O2. Preventing these parasitic reactions, in particular by developing more stable solvents/electrolytes, is critical for progress. Dimethyl sulfoxide (DMSO) is a promising solvent for Li-O2 battery applications [1], but there are conflicting opinions on the long-term stability of DMSO. Experimental work by Kwabi et al. [2] and computational results by Laino et al. [3] suggest that DMSO is readily oxidized to dimethyl sulfone (DMSO2) at Li2O2 surfaces – also forming LiOH. These results have, however, recently been challenged by Schroeder et al. [4], claiming that DMSO is sufficiently stable in the presence of Li2O2, as long as there are no sources of acidic protons present (e.g. from water impurities or carbon electrodes) that can initiate decomposition by forming more reactive hydroperoxy species. More fundamental research on the reaction mechanisms of DMSO with reduced oxygen species is needed to resolve this contradiction. In this work we make use of quantum chemistry calculations to model alternative DMSO decomposition mechanisms in gas, solution phase, and at surfaces. We present reaction energies and barriers to reactions for proton abstraction (DMSO-H), methyl abstraction (DMSO-CH3), and addition reactions (DMSO2) with the aim of better understanding the relative importance of different reaction pathways and the impact of the reactants immediate environment.
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| 34. |
- Shirshova, N., et al.
(författare)
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Structural supercapacitor electrolytes based on bicontinuous ionic liquid-epoxy resin systems
- 2013
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 1:48, s. 15300-15309
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Tidskriftsartikel (refereegranskat)abstract
- 'Structural electrolytes' retain the desirable mechanical characteristics of structural (epoxy) resins whilst introducing sufficient ionic conductivity to operate as electrolytes in electrochemical devices. Here, a series of ionic liquid-epoxy resin composites were prepared to identify the optimum system microstructure required to achieve a high level of multifunctionality. The ionic conductivity, mechanical properties, thermal stability and morphology of the cured epoxy based structural electrolytes were studied as a function of phase composition for three fully formulated high performance structural epoxy systems. At only 30 wt% of structural resin and 70 wt% of ionic liquid based electrolyte, stiff monolithic plaques with thicknesses of 2-3 mm were obtained with a room temperature ionic conductivity of 0.8 mS cm-1 and a Young's modulus of 0.2 GPa. This promising performance can be attributed to a long characteristic length scale spinodal microstructure, suggesting routes to further optimisation in the future. © 2013 The Royal Society of Chemistry.
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| 35. |
- Wilken, Susanne, 1983, et al.
(författare)
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Initial stages of thermal decomposition of LiPF6-based lithium ion battery electrolytes by detailed Raman and NMR spectroscopy
- 2013
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 3:37, s. 16359-16364
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Tidskriftsartikel (refereegranskat)abstract
- Independent of the specific electrode chemistry, the state-of-the-art lithium ion battery electrolytes based on LiPF6 in organic solvents have a low thermal abuse tolerance and poor cycle life at elevated temperatures. We present here a detailed investigation of the initial stages of the thermal decomposition of LiPF6 in EC/DMC stored at 85 degrees C using Raman and NMR spectroscopy. During storage (up to 160 h), significant amounts of CO2 are evolved, as detected in the Raman spectra. Time-resolved H-1, P-31, and F-19 NMR spectra show the evolution of POF3, POF(OH)(2), POF2(OCH2CH2)(n)F, and POF2OMe as reactive decomposition products. Our unique F-19 NMR approach, measuring while heating with both high energy and time resolution, allows for a first quantitative analysis of the evolved species and reveals several decomposition reactions during the first 30 min up to 72 h, where the rates of HF and POF2OMe formation are surprisingly linear. EC is found to be much less reactive compared to DMC. All information is used in the formulation of an updated decomposition pathway chart for LiPF6 based electrolytes.
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| 36. |
- Wilken, Susanne, 1983, et al.
(författare)
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Ionic Liquids in Lithium Battery Electrolytes: Composition versus Safety and Physical Properties
- 2015
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 275, s. 935-942
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Tidskriftsartikel (refereegranskat)abstract
- Ionic liquids have been highlighted as non-flammable, environmentally friendly, and suggested as possible solvents in lithium ion battery electrolytes. Here, the application of two ionic liquids from the EMIm-family in a state-of-the-art carbonate solvent based electrolyte is studied with a focus on safety improvement. The impact of the composition on physical and safety related properties is investigated for IL concentrations of additive (similar to 5 wt%) up to co-solvent concentrations (similar to 60 wt%). Furthermore, the role of the lithium salt concentration is separately addressed by studying a set of electrolytes at 0.5 M, 1 M, and 2 M LiPF6 concentrations. A large impact on the electrolyte properties is found for the electrolytes containing EMImTFSI and high salt concentrations. The composition 2 M LiPF6 EC:DEC:IL (1:1:3 wt%) is found non-flammable for both choices of ILs added. The macroscopic observations are complemented by a Raman spectroscopy analysis whereby a change in the Li+ solvation is detected for IL concentrations >4.5 mol%.
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| 37. |
- 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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| 38. |
- Younesi, Reza, et al.
(författare)
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Ether Based Electrolyte, LiB(CN)4 Salt and Binder Degradation in the Li-€“O2 Battery Studied by Hard X-ray Photoelectron Spectroscopy (HAXPES)
- 2012
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 116:35, s. 18597-18604
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Tidskriftsartikel (refereegranskat)abstract
- Li-O2 cells composed of a carbon cathode containing an α-MnO2 nanowire catalyst and a Kynar (PVDF-HFP) binder were cycled with different electrolytes containing 0.5 M LiB(CN)4 salt in polyethylene glycol dimethyl ether (PEGDME) or tetraethylene glycol dimethyl ether (Tetraglyme) solvents. All cells exhibited fast capacity fading. To explain this, the surface chemistry of the carbon electrodes were investigated by synchrotron based hard X-ray photoelectron spectroscopy (HAXPES) using two photon energies of 2300 and 6900 eV. It is shown that the LiB(CN)4 salt and Kynar binder were degraded during cycling, forming a layer composed of salt and binder residues on the cathode surface. The degradation mechanism of the salt differed in the two tested solvents and, consequently, different types of boron compounds were formed during cycling. Larger amounts of the degraded salt was observed using Tetraglyme as the solvent. With a nonfluorined Li-salt, the observed formation of LiF, which might be a reason for the observed blockage of pores in the cathode and for the observed capacity fading, must be due to Kynar binder decomposition. The amount of LiF formed in the PEGDME cell was larger than that formed in the Tetraglyme cell. The results indicate that not only the electrolyte solvent, but also electrolyte salt as well as the binder used for the porous cathode must be carefully considered when building a successful rechargeable Li-O2 battery.
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