| 1. |
- Forestier, C., et al.
(författare)
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Facile reduction of pseudo-carbonates: Promoting solid electrolyte interphases with dicyanoketene alkylene acetals in lithium-ion batteries
- 2016
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 303, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Dicyanoketene ethylene and propylene acetals, DCKEA and DCKPA respectively, have been investigated as electrolyte additives for Li-ion batteries. The purpose was to assess the changes in reduction behaviour and solid electrolyte interphase (SEI) passivation properties upon replacing the carbonyl group of ethylene carbonate (EC) and propylene carbonate (PC) solvents, respectively, by the slightly more electronegative and highly conjugated =C(CN)(2) group. The experimental reduction potentials and the IR spectroscopy characterisation efforts were further supported by density functional theory (DFT) computations. The two additives were found to, in relatively small amount (0.5 wt%), provide beneficial effects on the capacity retention of 8 mAh cells cycled at 20 and 45 degrees C. Moreover, the additives proved to enhance the thermal stability of the lithiated graphite/electrolyte interface, as deduced from DSC measurements.
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| 2. |
- Jankowski, Piotr, 1990, et al.
(författare)
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New boron based salts for lithium-ion batteries using conjugated ligands
- 2016
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 18:24, s. 16274-16280
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Tidskriftsartikel (refereegranskat)abstract
- A new anion design concept, based on combining a boron atom as the central atom and conjugated systems as ligands, is presented as a route for finding alternative Li-salts for lithium-ion batteries. The properties of a wide range of novel anions designed in this way have been evaluated by DFT calculations focusing on three different fundamental success factors/measures: the strength of the cation-anion interaction, ultimately determining both the solubility and the ionic conductivity, the oxidation limit, determining their possible use vs. high voltage cathodes, and the reduction stability, revealing a possible role of the anion in the SEI-formation at the anode. For a few anions superior properties vs. today's existing or suggested anions are predicted, especially the very low cation-anion interaction strengths are promising features. The design route itself is shown to be versatile in determining the correlation between different choices of ligands and the resulting overall properties - where the most striking feature is the decreased lithium cation interaction energy upon using the (1Z,3Z)-buta-1,3-diene-1,2,3,4-tetracarbonitrile ligands. This also opens avenues for the further design of novel anions beyond those with a boron central atom.
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| 3. |
- Jankowski, Piotr, 1990, et al.
(författare)
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Understanding of Lithium 4,5-Dicyanoimidazolate-Poly(ethylene oxide) System: Influence of the Architecture of the Solid Phase on the Conductivity
- 2016
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 120:41, s. 23358-23367
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Tidskriftsartikel (refereegranskat)abstract
- Solid polymer electrolytes (SPEs) with high lithium conductivity are very beneficial as a safe material for lithium battery applications. Herein we present new set of a SPEs based on lithium 2-trifluoromethyl-4,5-dicyanoimidazolate (LiTDI) with wide range of ether oxygen to lithium molar ratios. The phase composition was characterized in detail with thermal, diffraction, and spectroscopic techniques, and its influence on conductivity behavior was examined. Two detected crystalline phases of LiTDI poly(ethylene oxide) (PEO) were simulated with computational methods. The obtained results allowed insight into the structure of these electrolytes and helped us to understand on the molecular level factors influencing electrochemical properties and phase behavior. It was shown that ability to form a low-melting phase can be used to lower the temperature window of operation. That made it possible to keep such SPEs amorphous at 30 degrees C during 80 days. The thermal stability of the samples was checked to prove the safety of the electrolytes.
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