| 1. |
- Asfaw, Habtom D., et al.
(författare)
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Boosting the thermal stability of emulsion–templated polymers via sulfonation : an efficient synthetic route to hierarchically porous carbon foams
- 2016
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Ingår i: ChemistrySelect. - : Wiley. - 2365-6549. ; 1:4, s. 784-792
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Tidskriftsartikel (refereegranskat)abstract
- Hierarchically porous carbon foams with specific surface areas exceeding 600 m2 g−1 can be derived from polystyrene foams that are synthesized via water-in-oil emulsion templating. However, most styrene-based polymers lack strong crosslinks and are degraded to volatile products when heated above 400 oC. A common strategy employed to avert depolymerization is to introduce potential crosslinking sites such as sulfonic acids by sulfonating the polymers. This article unravels the thermal and chemical processes leading up to the conversion of sulfonated high internal phase emulsion polystyrenes (polyHIPEs) to sulfur containing carbon foams. During pyrolysis, the sulfonic acid groups (-SO3H) are transformed to sulfone (-C-SO2-C-) and then to thioether (-C−S-C-) crosslinks. These chemical transformations have been monitored using spectroscopic techniques: in situ IR, Raman, X-ray photoelectron and X-ray absorption near edge structure spectroscopy. Based on thermal analyses, the formation of thioether links is associated with increased thermal stability and thus a substantial decrease in volatilization of the polymers.
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| 2. |
- Dietrich, Paul M., et al.
(författare)
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Near ambient pressure-x-ray photoelectron spectroscopy spectra of lithium bis (trifluoromethane-sulfonyl) imide in propylene carbonate
- 2023
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Ingår i: Surface Science Spectra. - : American Vacuum Society. - 1055-5269 .- 1520-8575. ; 30:1
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Tidskriftsartikel (refereegranskat)abstract
- Near ambient pressure-x-ray photoelectron spectroscopy (NAP-XPS) is a less traditional form of XPS that allows samples to be analyzed at relatively high pressures, i.e., at greater than 5000 Pa. NAP-XPS can probe moderately volatile liquids, biological samples, porous materials, and/or polymeric materials that outgas significantly. In this submission, we show the survey, Li 1s, S 2p, C 1s, N 1s, O 1s, and F 1s NAP-XPS spectra of a Li-based electrolyte solution, which is a material that would be difficult to analyze by conventional XPS. The measurements were performed at 200 Pa in ambient gas atmosphere to compensate for surface charging. Peak fits of the C 1s, O 1s, and F 1s narrow scans are presented.
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| 3. |
- Edström, Kristina, et al.
(författare)
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Electrode/electrolyte interfaces in lithium and sodium batteries
- 2017
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Konferensbidrag (refereegranskat)abstract
- Lithium-ion batteries (LIB) and sodium-ion batteries (SIB) and their materials is today a large research area due to the practical need for efficient energy storage. SIBs show, compared to LIBs, unique electrochemical reactions that mechanistically need to be understood. The kind of materials that can host sodium ions are, for instance, structurally different from the negative and positive electrode materials for LIBs. Also interfacial reactions occurring between the electrode and the electrolyte are different from LIBs. To understand the chemical properties of electrolyte/electrode interfaces in LIBs and SIBs is one of the core research activities at the Ångström Advanced Battery Centre (ÅABC), Uppsala University. It is at these interfaces, the solid-electrolyte interphase (SEI) on the anode and the cathode electrolyte interface (CEI) on the cathode, charge transfer reactions take place, unwanted side reactions might start and the stability of the interface also influence the thermal stability of the battery. Careful characterization is therefore needed as a base for creating new and more stable interfaces for prolonged battery life. In this presentation we will make a review of several studies we have performed combining electrochemical characterization with in-house and synchrotron-based photoelectron spectroscopy (such as hard X-ray Photoelectron Spectroscopy, HAXPES). We will primarily dwell on the difference in chemical composition of the SEI of anodes used in LIBs and SIBs, respectively. We will also give some examples of ways to improve cycle life: the role of the electrolyte salt, electrolyte additives, but also of ways to protect electrode particle surfaces. We have investigated materials from three different categories of anodes: i.e. conversion, alloying, and insertion anodes. Our HAXPES results on Fe2O3 as a conversion anode material indicated that the SEI on Fe2O3 anode is thicker and more homogeneous in a SIB compared to that in an analogue Li-ion battery.1 We will discuss our work of silicon anodes for LIBs and we will discuss the dissolution of the SEI components in a SIB which is larger than for a LIB2. We will discuss the results which show that the SEI on a carbonacous anode in a SIB is inferior to that of the LIB counterpart. The interfaces of positive electrodes are also important. Often corrosion products will form during battery cycling leading to metal dissolution and poisoning of the negative electrode. We will also here compare the interfaces of Ni- and Mn-based oxide cathodes for LIBs and SIBs3.. References: [1] B. Philippe; M. Valvo; F. Lindgren; H. Rensmo; K. Edström, Chem. Mater. 2014, 26, 5028–5041.[2] R. Mogensen, D. Brandell, R. Younesi, ACS Energy Lett., 2016, 1, 1173–1178.[3] S. Doubaji, B. Philippe, I. Saadoune, M. Gorgoi, T. Gustafsson, A. Solhy, Mario Valvo, H. Rensmo, K. Edström. ChemSusChem, 2916, 9, 97-108.
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| 4. |
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| 5. |
- Farhat, Douaa, et al.
(författare)
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Adiponitrile-Lithium Bis(trimethylsulfonyl)imide Solutions as Alkyl Carbonate-free Electrolytes for Li4Ti5O12 (LTO)/LiNi1/3Co1/3Mn1/3O2 (NMC) Li-Ion Batteries
- 2017
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Ingår i: ChemPhysChem. - : WILEY-V C H VERLAG GMBH. - 1439-4235 .- 1439-7641. ; 18:10, s. 1333-1344
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Tidskriftsartikel (refereegranskat)abstract
- Recently, dinitriles (NC(CH2)(n)CN) and especially adiponitrile (ADN, n = 4) have attracted attention as safe electrolyte solvents owing to their chemical stability, high boiling points, high flash points, and low vapor pressure. The good solvation properties of ADN toward lithium salts and its high electrochemical stability (approximate to 6 V vs. Li/Li+) make it suitable for safer Li-ions cells without performance loss. In this study, ADN is used as a single electrolyte solvent with lithium bis(trimethylsulfonyl) imide (LiTFSI). This electrolyte allows the use of aluminium collectors as almost no corrosion occurs at voltages up to 4.2 V. The physicochemical properties of the ADN-LiTFSI electrolyte, such as salt dissolution, conductivity, and viscosity, were determined. The cycling performances of batteries using Li4Ti5O12 (LTO) as the anode and LiNi1/3Co1/3Mn1/3O2 (NMC) as the cathode were determined. The results indicate that LTO/NMC batteries exhibit excellent rate capabilities with a columbic efficiency close to 100 %. As an example, cells were able to reach a capacity of 165 mAhg(-1) at 0.1C and a capacity retention of more than 98% after 200 cycles at 0.5 C. In addition, electrodes analyses by SEM, X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy after cycling confirming minimal surface changes of the electrodes in the studied battery system.
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| 6. |
- Farhat, Douaa, et al.
(författare)
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Towards high-voltage Li-ion batteries : Reversible cycling of graphite anodes and Li-ion batteries in adiponitrile-based electrolytes
- 2018
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Ingår i: Electrochimica Acta. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0013-4686 .- 1873-3859. ; 281, s. 299-311
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Tidskriftsartikel (refereegranskat)abstract
- Due to their low vapor pressure and their promising electrochemical and thermal stability, N C- (CH2)n-C N dinitriles are proposed as an electrolyte solvent for Li-ion batteries. Adiponitrile (ADN) has substantial advantages, especially for applications requiring high potential cathodes, because it has high electrochemical/thermal stability (up to 6 V vs. Li/Li+, > 120 degrees C). However, to obtain very high voltage batteries, ADN electrolytes must also passivate the anode of the battery. In this work, reversible cycling of graphite in adiponitrile was successfully achieved by adding a few percent of fluoroethylene carbonate allowing the realization of Graphite/NMC Li-ion battery. The battery of specific capacity of 135 mAhh.g(-1) showed a cycling stability for more than 40 cycles. The composition of the solid electrolyte interphase (SEI) was determined as a function of the FEC concentration as well as the state of charge of the graphite anode using hard X-ray photoelectron spectroscopy (HAXPES) and XPS. With FEC, the SEI layer is thinner and depends on the SOC of the anode, but does not depend on the FEC concentration. SEM characterizations clearly showed that the surface of the anode is completely covered by the SEI layer, regardless of the concentration of FEC. Indeed, 2% of FEC is sufficient to suppress the reduction of adiponitrile which is explained by a specific adsorption of FEC on the graphite anode.
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| 7. |
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| 8. |
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| 9. |
- Jeschull, Fabian, et al.
(författare)
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On the Electrochemical Properties and Interphase Composition of Graphite : PVdF-HFP Electrodes in Dependence of Binder Content
- 2017
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Ingår i: Journal of the Electrochemical Society. - : Electrochemical Society. - 0013-4651 .- 1945-7111. ; 164:7, s. A1765-A1772
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Tidskriftsartikel (refereegranskat)abstract
- Poly(vinylidene-difluoride) (PVdF) based polymers constitute the most commonly used binders for lithium-ion battery electrodes. In scientific studies, the binder content often exceeds commercially meaningful amounts. At the same time, the battery electrode performance can in various ways be coupled to its binder content, partly due to its influence on the surface properties. For example, an optimum binder content of around 5 wt% has been reported. In this study, graphite: PVdF-HFP electrodes containing 2.5, 5 and 10 wt% of PVdF-HFP are investigated, and their electrochemical behavior are put into context of the electrode-electrolyte interphase of the different formulations. Although the electrodes display similar electrochemical behavior, the SEI layer composition and thickness, analyzed by photoelectron spectroscopy, vary notably depending on binder content. It was found that a binder content of 5 wt% maintained the best cycling stability and also exhibited a thinner SEI layer with a larger fraction of inorganic components. In contrast to higher binder contents, where the binder covers most of the surface, larger parts of the active material are exposed directly to the electrolyte with binder contents of 2.5-5 wt%. The formation of a thinner, yet protective, SEI layer is beneficial for cycling performance of the graphite electrode. (C) 2017 The Electrochemical Society. All rights reserved.
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| 10. |
- Jeschull, Fabian, et al.
(författare)
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Solid Electrolyte Interphase (SEI) of Water-Processed Graphite Electrodes Examined in a 65 mAh Full Cell Configuration
- 2018
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 1:10, s. 5176-5188
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Tidskriftsartikel (refereegranskat)abstract
- Electrode binders, such as sodium carboxymethyl cellulose (CMC-Na), styrene–butadiene rubber (SBR) and poly(sodium acrylate) (PAA-Na) are commonly applied binder materials for the manufacture of electrodes from aqueous slurries. Their processability in water has considerable advantages over slurries based on N-methylpyrrolidone (NMP) considering toxicity, environment and production costs. In this study, water-processed graphite electrodes containing either CMC-Na:SBR, PAA-Na, or CMC-Na:PAA-Na as binders have been prepared on a pilot scale, cycled in graphite||LiFePO4 Li-ion battery cells and analyzed post-mortem with respect to the binder impact on the SEI composition, using in-house (1486.6 eV) and synchrotron-based (2300 eV) photoelectron spectroscopy (PES). The estimated SEI layer thickness was smaller than 11 nm for all samples and decreased in the order: PAA-Na > CMC-Na:SBR > CMC-Na:PAA-Na. The SEI thickness correlates with the surface concentration of CMC-Na, for example, the CMC-Na:PAA-Na mixture showed signs of polymer depletion of the PAA-Na component. The SEI layer components are largely comparable to those formed on a conventional graphite:poly(vinylidene difluoride) (PVdF) electrode. However, the SEI is complemented, by notable amounts of carboxylates and alkoxides, whose formation is favored in water-based negative electrodes. Additionally, more electrolyte salt degradation is observed in formulations comprising PAA-Na. The choice of the binder for the negative electrode had little impact on the surface layer formed on the LiFePO4 positive electrode, except for different contents of sodium salt deposits, as a result of ion migration from the counter electrode.
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