| 1. |
- 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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| 2. |
- 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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