| 1. |
- 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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| 2. |
- Kerner, Manfred, 1984, et al.
(författare)
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Thermal stability and decomposition of lithium bis(fluorosulfonyl)imide (LiFSI) salts
- 2016
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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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| 3. |
- Plylahan, Nareerat, 1984, et al.
(författare)
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Ionic liquid and hybrid ionic liquid/organic electrolytes for high temperature lithium-ion battery application
- 2016
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686. ; 216, s. 24-34
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Tidskriftsartikel (refereegranskat)abstract
- Ionic liquid (IL) and hybrid IL/organic electrolytes with pyrrolidinium cation based ILs have been investigated for application in high temperature lithium-ion batteries (HT-LIBs). The IL based electrolytes show high thermal stabilities, up to 340 degrees C, ionic conductivities of > 5 x 10(-3) S cm(-1) at 80 degrees C, and broad electrochemical stability windows: 0-5 V vs. Li+/Li degrees. The performance of LiFePO4 based half-cells at 80 degrees C is promising, delivering ca. 160 mAh g(-1) at 1C, with a rate capability up to 4C and ca. 98% coulombic efficiency. The creation of hybrid IL/organic electrolytes by adding different organic cyclic carbonate solvents reduces viscosity of the electrolytes by 28% at 80 degrees C, thereby improving the ion transport, and further improves the electrochemical performance; higher stability, better rate capability, and >= 99% coulombic efficiency. Overall, the electrolytes proposed have a potential to be applied in HT-LIBs, a concept with large advantages at the vehicle system level. (C) 2016 Elsevier Ltd. All rights reserved.
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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
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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. |
- Kerner, Manfred, 1984
(författare)
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Ionic Liquid Based Electrolytes for High-Temperature Lithium-Ion Batteries
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Today, lithium-ion batteries (LIBs) are ubiquitous in mobile phones, laptops, and other portable devices. The research community strives to further improve the LIB to increase electric driving distance and efficiency of both hybrid electric vehicles (HEVs) and fully electric vehicles (EVs). Conventional LIBs need to be strictly temperature controlled, most often cooled, to ca. 30°C, to ensure an acceptable and predictable life-time. Increasing the thermal stability and hence making possible operating temperatures of up to ca. 100°C would enable a merging of the cooling systems of the LIB and the power electronics – resulting in an overall reduced system complexity, saved mass, and a higher energy efficiency. All components of the LIB must be thermally stable to deliver the targeted performance and life-time. The electrolytes of conventional LIB all contain organic solvents and lithium salts, the former flammable with high vapour pressures and the latter meta-stable at room temperature and unstable at temperatures above 60°C. Thus more stable solvents and salts are needed to improve the inherent safety of the electrolyte – especially if aiming at elevated operating temperatures. In this thesis one possible alternative is investigated in the form of ionic liquid (IL) based electrolytes. ILs often exhibit properties advantageous for electrolytes: low vapour pressures, high thermal stabilities, low flammabilities, and high ionic conductivities. The physico-chemical properties of several IL based electrolytes have been assessed and furthermore a detailed characterization of several commercial sources of an often used electrolyte Li-salt has been performed.
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| 6. |
- Kerner, Manfred, 1984
(författare)
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Pure, Hybrid and Polymerized Ionic Liquid Based Electrolytes For High Temperature Lithium-Ion Battery Application
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Today, lithium-ion batteries (LIBs) are ubiquitous in mobile phones, laptops, and other portable devices. Additionally, LIBs are becoming more and more popular for powering hybrid and electric vehicles. The research community strives to further improve the LIBs to increase electric driving distance and efficiency of both hybrid and fully electric vehicles. Conventional LIBs need to be strictly temperature controlled, most often cooled, to ca. 30°C, to ensure an acceptable and predictable life-time. Increasing the thermal stability and hence making possible operating temperatures of up to ca. 100°C would enable a merging of the cooling systems of the LIB and the power electronics – resulting in an overall reduced system complexity, saved mass, and a higher energy efficiency.All components of the LIB must be thermally stable to deliver the targeted performance and life-time. The electrolytes of conventional LIBs all contain organic solvents and lithium salts, the former flammable with high vapour pressures and the latter meta-stable at room temperature and unstable at temperatures above 60°C. Thus more stable solvents and salts are needed to improve the inherent safety of the electrolyte – especially if aiming at elevated operating temperature applications.In this thesis procedures to investigate electrolytes for viability in HT-LIBs are demonstrated by investigating novel high-temperature LIB electrolyte alternatives primarily in the form of pure, hybrid and polymerized ionic liquid based systems. For several of these, physico-chemical properties such as viscosity, thermal stability, flammability and electrochemical stability window have been assessed and correlated with molecular level interactions, and furthermore a detailed characterization of several commercial sources of an often used electrolyte Li-salt has been performed.
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| 7. |
- Kerner, Manfred, 1984, et al.
(författare)
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Pyrrolidinium FSI and TFSI-Based Polymerized Ionic Liquids as Electrolytes for High-Temperature Lithium-Ion Batteries
- 2018
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Ingår i: Batteries. - : MDPI AG. - 2313-0105. ; 4:1
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Tidskriftsartikel (refereegranskat)abstract
- Promising electrochemical and dynamical properties, as well as high thermal stability, have been the driving forces behind application of ionic liquids (ILs) and polymerized ionic liquids (PILs) as electrolytes for high-temperature lithium-ion batteries (HT-LIBs). Here, several ternary lithium-salt/IL/PIL electrolytes (PIL el ) have been investigated for synergies of having both FSI and TFSI anions present, primarily in terms of physico-chemical properties, for unique application in HT-LIBs operating at 80 ◦ C. All of the electrolytes tested have low T g and are thermally stable ≥100 ◦ C, and with TFSI as the exclusive anion the electrolytes (set A) have higher thermal stabilities ≥125 ◦ C. Ionic conductivities are in the range of 1 mS/cm at 100 ◦ C and slightly higher for set A PIL el , which, however, have lower oxidation stabilities than set B PIL el with both FSI and TFSI anions present: 3.4–3.7 V vs. 4.2 V. The evolution of the interfacial resistance increases for all PIL el during the first 40 h, but are much lower for set B PIL el and generally decrease with increasing Li-salt content. The higher interfacial resistances only influence the cycling performance at high C-rates (1 C), where set B PIL el with high Li-salt content performs better, while the discharge capacities at the 0.1 C rate are comparable. Long-term cycling at 0.5 C, however, shows stable discharge capacities for 100 cycles, with the exception of the set B PIL el with high Li-salt content. Altogether, the presence of both FSI and TFSI anions in the PIL el results in lower ionic conductivities and decreased thermal stabilities, but also higher oxidation stabilities and reduced interfacial resistances and, in total, result in an improved rate capability, but compromised long-term capacity retention. Overall, these electrolytes open for novel designs of HT-LIBs.
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| 8. |
- 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
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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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