| 1. |
- Lindberg, Simon, 1987, et al.
(författare)
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Charge storage mechanism of α-MnO2 in protic and aprotic ionic liquid electrolytes
- 2020
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 460
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Iselau, Frida, 1979, et al.
(författare)
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Competitive adsorption of amylopectin and amylose on cationic nanoparticles: a study on the aggregation mechanism
- 2016
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-6848 .- 1744-683X. ; 12:14, s. 3388-3397
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Tidskriftsartikel (refereegranskat)abstract
- In this study we investigate the interactions between cationic nanoparticles and anionic starch, where the starch was composed of 20 wt% of amylose, a linear polymer, and 80 wt% of amylopectin, a branched polymer. The mechanism of aggregation was investigated by scattering techniques. It was found that the cationic particles formed large aggregates with the starch as a result of selective adsorption of the amylopectin. Amylose did not participate significantly in the aggregate formation even when the charge ratio of starch to particles was <1. For starch to particle ratio 41 stabilization was recovered mostly due to the large hindrance brought about by the highly branched amylopectin. This results in a shift of the stabilization mechanism from electrostatic to electrosteric. The internal structure of the aggregates was composed of primary particles with starch coils adsorbed on the surface. This information supports the proposed aggregation mechanism, which is based on adsorption of the negatively charged starch in patches on the positively charged nanoparticles causing attractive interaction between the particles.
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| 3. |
- Xiong, Shizhao, 1985, et al.
(författare)
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Role of organic solvent addition to ionic liquid electrolytes for lithium–sulphur batteries
- 2015
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069.
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the role of the addition of an organic solvent to an ionic liquid electrolyte for the performance of lithium–sulphur (Li–S) batteries. We find that with a mixed electrolyte, formed by adding 10 wt% 1,3-dioxolane (DIOX) to an ionic liquid, the capacity of a Li–S cell is more than doubled, the rate capability and the cycling performance considerably improved, compared to a cell utilizing a neat ionic liquid electrolyte. The improved performance can be correlated with an enhanced ion transport, evidenced by an increased ionic conductivity and higher limiting current density, directly related to a decrease in viscosity and glass transition temperature of the mixed electrolytes. We show that this in turn is linked to a change in the local environment of the Li-ions where the organic solvent is incorporated in the coordination shell. In addition we show that the mixed electrolytes have a considerably higher thermal stability, in particular a dramatically increased flash point, and improved low temperature properties with respect to a conventional organic solvent based electrolyte currently used for Li–S batteries.
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| 4. |
- Lindberg, Simon, 1985, et al.
(författare)
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A VO2 based hybrid super-capacitor utilizing a highly concentrated aqueous electrolyte for increased potential window and capacity
- 2020
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686. ; 345
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Tidskriftsartikel (refereegranskat)abstract
- In this work we demonstrate the application of a highly concentrated aqueous electrolyte to a hybrid supercapacitor cell. We combine an 8 m Sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) aqueous electrolyte with a nanostructured VO2-cathode to enhance the voltage widow up to 2.4 V in a full cell. With the enhanced potential window, we are able to exploit the full contribution of the VO2 material, where a part is outside the stability window of standard alkaline aqueous electrolytes. We show that the VO2 material in the highly concentrated electrolyte provides a faradaic contribution even at the highest current density (25 A/g) and in this way increases the energy content also in high power conditions. The full cell shows a good efficiency but also a capacity fade over 500 cycles (39%) which is most likely related to dissolution of VO2.
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| 5. |
- Martins, Murillo L., et al.
(författare)
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Raman and Infrared spectroscopies and X-ray diffraction data on bupivacaine and ropivacaine complexed with 2-hydroxypropyl−β−cyclodextrin
- 2017
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Ingår i: Data in Brief. - : Elsevier BV. - 2352-3409. ; 15, s. 25-29
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Tidskriftsartikel (refereegranskat)abstract
- The data presented in this article are related to the research article entitled “Probing the dynamics of complexed local anesthetics via neutron scattering spectroscopy and DFT calculations (http://dx.doi.org/10.1016/j.ijpharm.2017.03.051)” (Martins et al., 2017) [1]. This work shows the molecular and structural behavior of the local anesthetics (LAs) bupivacaine (BVC, C18H28N2O) and ropivacaine (RVC, C17H26N2O) before and after complexation with the water-soluble oligosaccharide 2-hydroxypropyl???cyclodextrin (HP-?-CD).
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| 6. |
- Agostini, Marco, 1987, et al.
(författare)
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Designing a Safe Electrolyte Enabling Long‐Life Li/S Batteries
- 2019
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Ingår i: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 12:18, s. 4176-4184
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Tidskriftsartikel (refereegranskat)abstract
- Lithium–sulfur (Li/S) batteries suffer from “shuttle” reactions in which soluble polysulfide species continuously migrate to and from the Li metal anode. As a consequence, the loss of active material and reactions at the surface of Li limit the practical applications of Li/S batteries. LiNO3 has been proposed as an electrolyte additive to reduce the shuttle reactions by aiding the formation of a stable solid electrolyte interphase (SEI) at the Li metal, limiting polysulfide shuttling. However, LiNO3 is continuously consumed during cycling, especially at low current rates. Therefore, the Li/S battery cycle life is limited by the LiNO3 concentration in the electrolyte. In this work, an ionic liquid (IL) [N-methyl-(n-butyl)pyrrolidinium bis(trifluoromethylsulfonyl)imide] was used as an additive to enable longer cycle life of Li/S batteries. By tuning the IL concentration, an enhanced stability of the SEI and lower flammability of the solutions were demonstrated, that is, higher safety of the battery. The Li/S cell built with a high sulfur mass loading (4 mg cm−2) and containing the IL-based electrolyte demonstrated a stable capacity of 600 mAh g−1 for more than double the number of cycles of a cell containing LiNO3 additive.
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| 7. |
- Karlsson, Maths, 1978, et al.
(författare)
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Structure of Proton-Conducting Alkali Thio-Hydroxogermanates
- 2008
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 1520-5002 .- 0897-4756. ; 20:19, s. 6014-6021
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Tidskriftsartikel (refereegranskat)abstract
- Using a combination of neutron diffraction, infrared spectroscopy, and first-principles calculations, we have investigated the structure of hydrated and dehydrated proton conducting alkali thio-hydroxogermanates of general formula M2GeS2(OH)2·yH2O (M = K, Rb, and Cs). The results show that the structure of hydrated and dry materials are basically the same, which confirms previous indications that the main effect of heating these materials is just a loss of water. We suggest that in the hydrated state the structure of these materials is built of dimers of thio-hydroxogermanate anions, with the water molecules acting as bridges between such dimers. In the dehydrated structure, the thio-hydroxogermanate anions instead form an extended network through the formation of interdimer hydrogen bonds through the −OH groups in the structure. The alkali ions are suggested to act as “space-fillers” in voids formed by the thio-hydroxogermanate anion dimers, in both the hydrated and the dehydrated state.
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| 8. |
- Rizell, Josef, 1996, et al.
(författare)
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Neutron Reflectometry Study of Solid Electrolyte Interphase Formation in Highly Concentrated Electrolytes
- 2023
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Ingår i: Small Structures. - : WILEY. - 2688-4062. ; 4:11
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Tidskriftsartikel (refereegranskat)abstract
- Highly concentrated electrolytes have been found to improve the cycle life and Coulombic efficiency of lithium metal anodes, as well as to suppress dendrite growth. However, the mechanism for these improvements is not well understood. Partly, this can be linked to the difficulty of accurately characterizing the solid electrolyte interphase (SEI), known to play an important role for anode stability and stripping/plating efficiency. Herein, in situ neutron reflectometry is used to obtain information about SEI formation in a highly concentrated ether-based electrolyte. With neutron reflectometry, the thickness, scattering length density (SLD), and roughness of the SEI layer formed on a Cu working electrode are nondestructively probed. The reflectivity data point to the formation of a thin (5 nm) SEI in the highly concentrated electrolyte (salt:solvent ratio 1:2.2), while a considerably thicker (13 nm) SEI is formed in an electrolyte at lower salt concentration (salt:solvent ratio 1:13.7). Further, the SEI formed in the electrolyte with high salt concentration has a higher SLD, suggesting that the chemical composition of the SEI changes. The results from neutron reflectometry correlate well with the electrochemical data from SEI formation.
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| 9. |
- Sun, Jinhua, 1987, et al.
(författare)
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Real-time imaging of Na+ reversible intercalation in "Janus" graphene stacks for battery applications
- 2021
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Ingår i: Science advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 7:22
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Tidskriftsartikel (refereegranskat)abstract
- Sodium, in contrast to other metals, cannot intercalate in graphite, hindering the use of this cheap, abundant element in rechargeable batteries. Here, we report a nanometric graphite-like anode for Na+ storage, formed by stacked graphene sheets functionalized only on one side, termed Janus graphene. The asymmetric functionalization allows reversible intercalation of Na+, as monitored by operando Raman spectroelectrochemistry and visualized by imaging ellipsometry. Our Janus graphene has uniform pore size, controllable functionalization density, and few edges; it can store Na+ differently from graphite and stacked graphene. Density functional theory calculations demonstrate that Na+ preferably rests close to -NH2 group forming synergic ionic bonds to graphene, making the interaction process energetically favorable. The estimated sodium storage up to C6.9Na is comparable to graphite for standard lithium ion batteries. Given such encouraging Na+ reversible intercalation behavior, our approach provides a way to design carbon-based materials for sodium ion batteries.
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| 10. |
- Iselau, Frida, 1979, et al.
(författare)
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Formation and relaxation kinetics of starch-particle complexes
- 2016
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Ingår i: Soft Matter. - 1744-6848 .- 1744-683X. ; 12:47, s. 9509-9519
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Tidskriftsartikel (refereegranskat)abstract
- The formation and relaxation kinetics of starch-particle complexes were investigated in this study. The combination of cationic nanoparticles in suspension and anionic starch in solution gave rise to aggregate formation which was studied by dynamic light scattering, revealing the initial adsorption of the starch molecules on the particle surface. By examining the stability ratio, W, it was found that even in the most destabilized state, i.e. at charge neutralization, the starch chains had induced steric stabilization to the system. At higher particle and starch concentrations relaxation of the aggregates could be seen, as monitored by a decrease in turbidity with time. This relaxation was evaluated by fitting the data to the Kohlrausch-Williams-Watts function. It was found that irrespective of the starch to particle charge ratio the relaxation time was similar. Moreover, a molecular weight dependence on the relaxation time was found, as well as a more pronounced initial aggregated state for the higher molecular weight starch. This initial aggregate state could be due to bridging flocculation. With time, as the starch chains have relaxed into a final conformation on the particle surface, bridging will be less important and is gradually replaced by patches that will cause patchwise flocculation. After an equilibration time no molecular weight dependence on aggregation could be seen, which confirms the patchwise flocculation mechanism.
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