| 1. |
- Sun, Bing, et al.
(author)
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Ion transport in polycarbonate based solid polymer electrolytes : experimental and computational investigations
- 2016
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In: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 18:14, s. 9504-9513
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Journal article (peer-reviewed)abstract
- Among the alternative host materials for solid polymer electrolytes (SPEs), polycarbonates have recently shown promising functionality in all-solid-state lithium batteries from ambient to elevated temperatures. While the computational and experimental investigations of ion conduction in conventional polyethers have been extensive, the ion transport in polycarbonates has been much less studied. The present work investigates the ionic transport behavior in SPEs based on poly(trimethylene carbonate) (PTMC) and its co-polymer with epsilon-caprolactone (CL) via both experimental and computational approaches. FTIR spectra indicated a preferential local coordination between Li+ and ester carbonyl oxygen atoms in the P(TMC20CL80) co-polymer SPE. Diffusion NMR revealed that the co-polymer SPE also displays higher ion mobilities than PTMC. For both systems, locally oriented polymer domains, a few hundred nanometers in size and with limited connections between them, were inferred from the NMR spin relaxation and diffusion data. Potentiostatic polarization experiments revealed notably higher cationic transference numbers in the polycarbonate based SPEs as compared to conventional polyether based SPEs. In addition, MD simulations provided atomic-scale insight into the structure-dynamics properties, including confirmation of a preferential Li+-carbonyl oxygen atom coordination, with a preference in coordination to the ester based monomers. A coupling of the Li-ion dynamics to the polymer chain dynamics was indicated by both simulations and experiments.
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| 2. |
- Oltean, Gabriel, et al.
(author)
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Towards Li-ion batteries operating at 80 °C: Ionic liquid versus conventional liquid electrolytes
- 2018
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In: Batteries. - : MDPI AG. - 2313-0105. ; 4, s. 2-6
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Journal article (peer-reviewed)abstract
- Li-ion battery (LIB) full cells comprised of TiO2-nanotube (TiO2-nt) and LiFePO4 (LFP)electrodes and either a conventional organic solvent based liquid electrolyte or an ionic liquid basedelectrolyte have been cycled at 80 °C. While the cell containing the ionic liquid based electrolyteexhibited good capacity retention and rate capability during 100 cycles, rapid capacity fading was found for the corresponding cell with the organic electrolyte. Results obtained for TiO2-nt and LFP half-cells indicate an oxidative degradation of the organic electrolyte at 80 °C. In all, ionic liquidbased electrolytes can be used to significantly improve the performance of LIBs operating at 80 °C.
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| 3. |
- Franco, Alejandro A., et al.
(author)
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Boosting Rechargeable Batteries R&D by Multiscale Modeling: Myth or Reality?
- 2019
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In: Chemical Reviews. - : American Chemical Society (ACS). - 0009-2665 .- 1520-6890. ; 119:7, s. 4569-4627
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Journal article (peer-reviewed)abstract
- This review addresses concepts, approaches, tools, and outcomes of multiscale modeling used to design and optimize the current and next generation rechargeable battery cells. Different kinds of multiscale models are discussed and demystified with a particular emphasis on methodological aspects. The outcome is compared both to results of other modeling strategies as well as to the vast pool of experimental data available. Finally, the main challenges remaining and future developments are discussed.
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| 4. |
- Lindberg, Simon, 1987, et al.
(author)
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Charge storage mechanism of α-MnO2 in protic and aprotic ionic liquid electrolytes
- 2020
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In: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 460
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Journal article (peer-reviewed)abstract
- In this work we have investigated the charge storage mechanism of MnO2 electrodes in ionic liquid electrolytes. We show that by using an ionic liquid with a cation that has the ability to form hydrogen bonds with the active material (MnO2) on the surface of the electrode, a clear faradaic contribution is obtained. This situation is found for ionic liquids with cations that have a low pKa, i.e. protic ionic liquids. For a protic ionic liquid, the specific capacity at low scan rate rates can be explained by a densely packed layer of cations that are in a standing geometry, with a proton directly interacting through a hydrogen bond with the surface of the active material in the electrode. In contrast, for aprotic ionic liquids there is no interaction and only a double layer contribution to the charge storage is observed. However, by adding an alkali salt to the aprotic ionic liquid, a faradaic contribution is obtained from the insertion of Li+ into the surface of the MnO2 electrode. No effect can be observed when Li+ is added to the protic IL, suggesting that a densely packed cation layer in this case prevent Li-ions from reaching the active material surface.
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| 5. |
- Younesi, Reza, et al.
(author)
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Li-O-2 Battery Degradation by Lithium Peroxide (Li2O2): A Model Study
- 2013
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In: Chemistry of Materials. - : American Chemical Society (ACS). - 1520-5002 .- 0897-4756. ; 25:1, s. 77-84
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Journal article (peer-reviewed)abstract
- The chemical stability of the Li-O-2 battery components (cathode and electrolyte) in contact with lithium peroxide (Li2O2) was investigated using X-ray photoelectron spectroscopy (XPS). XPS is a versatile method to detect amorphous as well as crystalline decomposition products of both salts and solvents. Two strategies were employed. First, cathodes including carbon, alpha-MnO2 catalyst, and Kynar binder (PVdF-HFP) were exposed to Li2O2 and LiClO4 in propylene carbonate (PC) or tetraethylene glycol dimethyl ether (TEGDME) electrolytes. The results indicated that Li2O2 degrades TEGDME to carboxylate containing species and that the decomposition products, in turn, degraded the Kynar binder. The alpha-MnO2 catalyst was unaffected. Second, Li2O2 model surfaces were kept in contact with different electrolytes to investigate the chemical stability and also the resulting surface layer on Li2O2. Further, the XPS experiments revealed that the Li salts such as LiPF6, LiBF4, and LiC!
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| 6. |
- Younesi, Reza, et al.
(author)
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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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In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 116:35, s. 18597-18604
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Journal article (peer-reviewed)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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| 7. |
- Bergman, Martin, 1985, et al.
(author)
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Graft copolymer electrolytes for high temperature Li-battery applications, using poly(methyl methacrylate) grafted poly(ethylene glycol)methyl ether methacrylate and lithium bis(trifluoromethanesulfonimide)
- 2015
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In: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 175, s. 96-103
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Journal article (peer-reviewed)abstract
- For successful hybridization of heavy vehicles, high temperature batteries might be the solution. Here, high temperature solid polymer electrolytes (SPE's) based on different ratios of poly(methyl methacrylate) (PMMA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA), with LiTFSI salt (at a fixed ether oxygen (EO):Li ratio of 20:1) have been prepared and investigated. The copolymers comprise PMMA backbones with grafted PEGMA side-chains containing 9 EO units. The SPE systems were characterized using Raman spectroscopy, broadband dielectric spectroscopy, differential scanning calorimetry, thermal gravimetric analysis, and electrochemical cycling in prototype cells, with a particular focus on the 83 wt% PEGMA system. The electrolytes have good thermal stabilities and dissociate the LiTFSI salt easily, while at the same time maintaining low glass transition temperatures (Tg's). Depending on the polymeric structure, ionic conductivities >1 mS cm-1 at 110 °C are detected, thus providing ion transport properties for a broad range of electrochemical applications. Prototype Li|polymer electrolyte|LiFePO4 cells utilizing the SPE at 60 °C showed surprisingly low capacities (
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| 8. |
- Jankowski, Piotr, 1990, et al.
(author)
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Prospects for Improved Magnesocene-Based Magnesium Battery Electrolytes
- 2021
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In: Batteries and Supercaps. - : Wiley. - 2566-6223. ; 4:8, s. 1335-1343
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Journal article (peer-reviewed)abstract
- Magnesium batteries are currently attracting a lot of interest as a next generation battery technology. One critical issue is to find a suitable electrolyte and herein we explore an electrolyte based on magnesocene (MgCp2) in tetrahydrofuran (THF), aiming for low-voltage Mg batteries, with respect to: Mg plating characteristics, electrochemical stability windows, electrolyte speciation, and electrolyte decomposition reactions; both experimentally and computationally. Overall, the electrolyte does not seem to decompose on a Mg metal anode and most likely reduced solvation of Mg2+ by the Cp- anion is important and species such as MgCp2THF2 may play an important role for Mg plating with small overpotential. The oxidation limit is largely determined by the Cp- anion and density functional theory predicted oxidation reactions point to polymerized end-products to be possible. Furthermore, in silico substitution studies enable us to establish the prospects of some Cp- anion derivatives to further improve the oxidative stability, but still the Mg2+ solvation must be monitored for ease of reduction and Mg plating.
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| 9. |
- Nilsson, Viktor, 1985, et al.
(author)
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Critical evaluation of the stability of highly concentrated LiTFSI - Acetonitrile electrolytes vs. graphite, lithium metal and LiFePO4 electrodes
- 2018
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In: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 384, s. 334-341
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Journal article (peer-reviewed)abstract
- Highly concentrated LiTFSI - acetonitrile electrolytes have recently been shown to stabilize graphite electrodes in lithium-ion batteries (LIBs) much better than comparable more dilute systems. Here we revisit this system in order to optimise the salt concentration vs. both graphite and lithium metal electrodes with respect to electrochemical stability. However, we observe an instability regardless of concentration, making lithium metal unsuitable as a counter electrode, and this also affects evaluation of e.g. graphite electrodes. While the highly concentrated electrolytes have much improved electrochemical stabilities, their reductive decomposition below ca. 1.2 V vs. Li + /Li° still makes them less practical vs. graphite electrodes, and the oxidative reaction with Al at ca. 4.1 V vs. Li + /Li° makes them problematic for high voltage LIB cells. The former originates in an insufficiently stable solid electrolyte interphase (SEI) dissolving and continuously reforming – causing self-discharge, as observed by paused galvanostatic cycling, while the latter is likely caused by aluminium current collector corrosion. Yet, we show that medium voltage LiFePO 4 positive electrodes can successfully be used as counter and reference electrodes.
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| 10. |
- Nilsson, Viktor, 1985, et al.
(author)
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Highly Concentrated LiTFSI-EC Electrolytes for Lithium Metal Batteries
- 2020
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In: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 3:1, s. 200-207
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Journal article (peer-reviewed)abstract
- Concentrated electrolytes have the potential to increase the stability for batteries with lithium metal anodes. In this study, liquid electrolytes were created by mixing ethylene carbonate (EC), a solid at room temperature, with a high concentration of LiTFSI salt. The binary LiTFSI-EC highly concentrated electrolytes have the benefit of extremely low volatility as compared to conventional organic electrolytes and also allow for cycling vs Li metal anodes. Using a LiTFSI-EC electrolyte with molar ratio 1:6, the Coulombic efficiency for Li plating/stripping on Cu is 97% at a current density of 1 mA cm-2 with a 2 mAh cm-2 capacity, pointing to a practically useful performance. In a full cell setup using a commercial LiFePO4 (LFP) cathode, the efficiency is maintained, proving compatibility. In comparison to other carbonate-based electrolytes, there is less accumulation of decomposition products on the surface of a cycled Li film, which in part explains the improved cycle life. In all, this electrolyte system shows promise in terms of electrochemical stability and may allow for safe Li metal batteries due to the inherent physical stability.
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