| 11. |
- Izzo, M. G., et al.
(författare)
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Rayleigh scattering and disorder-induced mixing of polarizations in amorphous solids at the nanoscale: 1-octyl-3-methylimidazolium chloride glass
- 2020
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Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 102:21
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Tidskriftsartikel (refereegranskat)abstract
- Acousticlike excitations in topologically disordered media at mesocale/nanoscale present anomalous features with respect to the Debye's theory. The so-called Rayleigh scattering manifests in a strong increase of the attenuation of the acousticlike excitations and a softening of the phase velocity with respect to its continuum limit value. Mean field models developed in the random media theory framework can successfully predict the occurrence, at the proper length scale, of Rayleigh scattering. The overall attenuation in the Rayleigh region is, however, underestimated. In the framework of random media theory we developed an analytical model, which permits a quantitative description of the acousticlike excitations in topological glasses in the whole first pseudo-Brillouin zone. The underestimation of the Rayleigh scattering is avoided and, importantly, the model allows to account also for the polarization properties of the acousticlike excitations. In a three-dimensional medium an acoustic wave is characterized by its phase velocity, intensity, and polarization. Rayleigh scattering emphasizes how the topological disorder affects the first two properties. The topological disorder is, however, expected to influence also the third one. In common with the Rayleigh scattering, hallmarks possibly related to the mixing of polarizations have been traced in different classes of amorphous solids at nanoscale. The quantitative theoretical approach developed permits to demonstrate how the mixing of polarizations generates a distinctive feature in the dynamic structure factor of amorphous solids. The modeling capability of the proposed mean field theory is tested on glassy 1-octyl-3-methylimidazolium chloride, whose spatial distribution of the elastic moduli is well assessed and can be experimentally characterized. Contrast between theoretical and experimental features for the selected glass reveals an excellent agreement. The mean field approach we present retains a certain degree of generality and can be possibly extended to different stochastic media or different wave fields.
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| 12. |
- Lee, Suyeong, et al.
(författare)
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Recent developments and future challenges in designing rechargeable potassium-sulfur and potassium-selenium batteries
- 2020
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Ingår i: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 13:11
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Tidskriftsartikel (refereegranskat)abstract
- The use of chalcogenide elements, such as sulfur (S) and selenium (Se), as cathode materials in rechargeable lithium (Li) and sodium (Na) batteries has been extensively investigated. Similar to Li and Na systems, rechargeable potassium-sulfur (K-S) and potassium-selenium (K-Se) batteries have recently attracted substantial interest because of the abundance of K and low associated costs. However, K-S and K-Se battery technologies are in their infancy because K possesses overactive chemical properties compared to Li and Na and the electrochemical mechanisms of such batteries are not fully understood. This paper summarizes current research trends and challenges with regard to K-S and K-Se batteries and reviews the associated fundamental science, key technological developments, and scientific challenges to evaluate the potential use of these batteries and finally determine effective pathways for their practical development.
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| 13. |
- 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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| 14. |
- 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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| 15. |
- Lindberg, Simon, 1985, et al.
(författare)
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Electrochemical Behaviour of Nb-Doped Anatase TiO2 Microbeads in an Ionic Liquid Electrolyte
- 2020
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Ingår i: Batteries and Supercaps. - : Wiley. - 2566-6223. ; 3:11, s. 1233-1238
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Tidskriftsartikel (refereegranskat)abstract
- TiO(2)is a promising material for high-power battery and supercapacitor applications. However, in general TiO(2)suffers from an initial irreversible capacity that limits its use in different applications. A combination of a microbead morphology, Nb-doping, and the use of an ionic liquid electrolyte is shown to significantly decrease the irreversible capacity loss. A change in the electrochemical response in the first cycles indicates formation of a solid-electrolyte interphase (SEI) or a modification of the structure of the surface layer of the TiO2/Nb microbeads, which apparently stabilises the performance. The change in the response is manifested in an increased charge transfer resistance and the presence of two charge transfer contributions. During prolonged cycling the TiO2/Nb electrode shows an excellent stability over 5000 cycles. Ex situ analysis after cycling shows that the overall microbead morphology is intact and that there are no changes in the crystal structure. However, a decrease in the intensity of the XRD pattern can point to a decrease in size of the nanocrystals building up the microbeads or the formation of amorphous phases.
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| 16. |
- Liu, Yangyang, et al.
(författare)
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Insight into the Critical Role of Exchange Current Density on Electrodeposition Behavior of Lithium Metal
- 2021
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Ingår i: Advanced Science. - : Wiley. - 2198-3844 .- 2198-3844. ; 8:5
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Tidskriftsartikel (refereegranskat)abstract
- Due to an ultrahigh theoretical specific capacity of 3860 mAh g−1, lithium (Li) is regarded as the ultimate anode for high-energy-density batteries. However, the practical application of Li metal anode is hindered by safety concerns and low Coulombic efficiency both of which are resulted fromunavoidable dendrite growth during electrodeposition. This study focuses on a critical parameter for electrodeposition, the exchange current density, which has attracted only little attention in research on Li metal batteries. A phase-field model is presented to show the effect of exchange current density on electrodeposition behavior of Li. The results show that a uniform distribution of cathodic current density, hence uniform electrodeposition, on electrode is obtained with lower exchange current density. Furthermore, it is demonstrated that lower exchange current density contributes to form a larger critical radius of nucleation in the initial electrocrystallization that results in a dense deposition of Li, which is a foundation for improved Coulombic efficiency and dendrite-free morphology. The findings not only pave the way to practical rechargeable Li metal batteries but can also be translated to the design of stable metal anodes, e.g., for sodium (Na), magnesium (Mg), and zinc (Zn) batteries.
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| 17. |
- Liu, Yangyang, et al.
(författare)
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Promoted rate and cycling capability of Li–S batteries enabled by targeted selection of co-solvent for the electrolyte
- 2020
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Ingår i: Energy Storage Materials. - : Elsevier BV. - 2405-8297. ; 25, s. 131-136
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Tidskriftsartikel (refereegranskat)abstract
- Lithium sulfur (Li–S) batteries are considered as promising candidates for high-energy-density battery systems owing to the high theoretical capacity of sulfur (1675 mAh g−1) and low cost of raw materials. However, their practical application is hampered by low rate capability and rapid degradation of capacity, arising from the passivation of the cathode by lithium sulfides (Li2S2/Li2S) deposited during discharge and low interfacial stability of the Li anode. Herein, we report on a comprehensive strategy to select co-solvent to the electrolyte to regulate the deposition of lithium sulfides during charge-discharge process. We show that addition of a co-solvent with high solubility, and strong interaction with Li2S to a conventional electrolyte effectively mitigates the formation of a passivating layer on the sulfur cathode and dramatically improves the interfacial stability of the Li anode. We demonstrate that Sulfolane (SL) has these properties and that a Li–S cell with an electrolyte containing 6 vol% SL exhibits outstanding cyclic performance (0.083% decay per cycle) and rate capability (capacity density of 765 mAh g−1 at rate of 1.0C). Thus, we provide a facile strategy for the selection of co-solvent for improved performance of Li–S batteries, realizing their practical application for high-energy-density battery systems.
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| 18. |
- Liu, Yangyang, et al.
(författare)
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Stable Li metal anode by crystallographically oriented plating through in-situ surface doping
- 2020
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Ingår i: Science China Materials. - : Springer Science and Business Media LLC. - 2199-4501 .- 2095-8226. ; 63:6, s. 1036-1045
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Tidskriftsartikel (refereegranskat)abstract
- Lithium (Li) metal is regarded as the holy grail anode material for high-energy-density batteries owing to its ultrahigh theoretical specific capacity. However, its practical application is severely hindered by the high reactivity of metallic Li against the commonly used electrolytes and uncontrolled growth of mossy/dendritic Li. Different from widely-used approaches of optimization of the electrolyte and/or interfacial engineering, here, we report a strategy of in-situ cerium (Ce) doping of Li metal to promote the preferential plating along the [200] direction and remarkably decreased surface energy of metallic Li. The in-situ Ce-doped Li shows a significantly reduced reactivity towards a standard electrolyte and, uniform and dendrite-free morphology after plating/stripping, as demonstrated by spectroscopic, morphological and electrochemical characterizations. In symmetric half cells, the in-situ Ce-doped Li shows a low corrosion current density against the electrolyte and drastically improved cycling even at a lean electrolyte condition. Furthermore, we show that the stable Li LiCoO2 full cells with improved coulombic efficiency and cycle life are also achieved using the Ce-doped Li metal anode. This work provides an inspiring approach to bring Li metal towards practical application in high energy-density batteries.
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| 19. |
- Lundin, Filippa, 1992, et al.
(författare)
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Pressure and Temperature Dependence of Local Structure and Dynamics in an Ionic Liquid
- 2021
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 125:10, s. 2719-2728
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Tidskriftsartikel (refereegranskat)abstract
- A detailed understanding of the local dynamics in ionic liquids remains an important aspect in the design of new ionic liquids as advanced functional fluids. Here, we use small-angle X-ray scattering and quasi-elastic neutron spectroscopy to investigate the local structure and dynamics in a model ionic liquid as a function of temperature and pressure, with a particular focus on state points (P,T) where the macroscopic dynamics, i.e., conductivity, is the same. Our results suggest that the initial step of ion transport is a confined diffusion process, on the nanosecond timescale, where the motion is restricted by a cage of nearest neighbors. This process is invariant considering timescale, geometry, and the participation ratio, at state points of constant conductivity, i.e., state points of isoconductivity. The connection to the nearest-neighbor structure is underlined by the invariance of the peak in the structure factor corresponding to nearest-neighbor correlations. At shorter timescales, picoseconds, two localized relaxation processes of the cation can be observed, which are not directly linked to ion transport. However, these processes also show invariance at isoconductivity. This points to that the overall energy landscape in ionic liquids responds in the same way to density changes and is mainly governed by the nearest-neighbor interactions.
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| 20. |
- Lundin, Filippa, 1992, et al.
(författare)
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Structure and dynamics of highly concentrated LiTFSI/acetonitrile electrolytes
- 2021
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 23:25, s. 13819-13826
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Tidskriftsartikel (refereegranskat)abstract
- High salt concentration has been shown to induce increased electrochemical stability in organic solvent-based electrolytes. Accompanying the change in bulk properties is a structural ordering on mesoscopic length scales and changes in the ion transport mechanism have also been suggested. Here we investigate the local structure and dynamics in highly concentrated acetonitrile electrolytes as a function of salt concentration. Already at low concentrations ordering on microscopic length scales in the electrolytes is revealed by small angle X-ray scattering, as a result of correlations of Li+ coordinating clusters. For higher salt concentrations a charge alternation-like ordering is found as anions start to take part in the solvation. Results from quasi-elastic neutron spectroscopy reveal a jump diffusion dynamical process with jump lengths virtually independent of both temperature and Li-salt concentration. The jump can be envisaged as dissociation of a solvent molecule or anion from a particular Li+ solvation structure. The residence time, 50-800 ps, between the jumps is found to be highly temperature and Li-salt concentration dependent, with shorter residence times for higher temperature and lower concentrations. The increased residence time at high Li-salt concentration can be attributed to changes in the interaction of the solvation shell as a larger fraction of TFSI anions take part in the solvation, forming more stable solvation shells.
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