| 91. |
- Lundin, Filippa, 1992, et al.
(författare)
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Ion Dynamics and Nanostructures of Diluted Ionic Liquid Electrolytes
- 2022
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 126:38, s. 16262-16271
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Tidskriftsartikel (refereegranskat)abstract
- Diluted ionic liquid electrolytes are promising candidates in next-generation batteries enabling the implementation of lithium metal anodes. The diluent should fully mix with the ionic liquid while not interacting with the Li ions to preserve the ionic liquid character, which is beneficial for Li-metal electrode stability. We report on the influence of a hydrofluoroether (HFE) diluent on ion dynamics and nanostructure of an ionic liquid electrolyte. We show that the ionic liquid and the diluent are fully miscible and that the solvation structure of the Li ions is not affected by the presence of HFE. The increase in the conductivity by the addition of the diluent is directly related to a decrease in viscosity with faster dynamics of all ionic species. However, the relative increase in mobility is considerably larger for the ionic liquid cation as a result of a preferred interaction with HFE. On the microscopic scale, more complex local non-Gaussian diffusive dynamics are found, faster than what is expected from the self-diffusion coefficient. The relative change of the dynamics with the addition of HFE on macro- and microscopic length scales correlates well, which underlines the connection between the motions probed on different length and time scales.
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| 92. |
- 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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| 93. |
- 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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| 94. |
- Maibach, Julia, 1984, et al.
(författare)
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Toward Operando Characterization of Interphases in Batteries
- 2023
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Ingår i: ACS Materials Letters. - 2639-4979. ; 5:9, s. 2431-2444
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Forskningsöversikt (refereegranskat)abstract
- Electrode/electrolyte interfaces are the most importantand leastunderstood components of Li-ion and next-generation batteries. Animproved understanding of interphases in batteries will undoubtedlylead to breakthroughs in the field. Traditionally, evaluating thoseinterphases involves using ex situ surface sensitiveand/or imaging techniques. Due to their very dynamic and reactivenature, ex situ sample manipulation is undesirable.From this point of view, operando surface sensitivetechniques represent a major opportunity to push boundaries in batterydevelopment. While numerous bulk spectroscopic, scattering, and imagingtechniques are well established and widely used, surface sensitive operando techniques remain challenging and, to a largerextent, restricted to the model systems. Here, we give a perspectiveon techniques with the potential to characterize solid/liquid interfacesin both model and realistic battery configurations. The focus is ontechniques that provide chemical and structural information at lengthand time scales relevant for the solid electrolyte interphase (SEI)formation and evolution, while also probing representative electrodeareas. We highlight the following techniques: vibrational spectroscopy,X-ray photoelectron spectroscopy (XPS), neutron and X-ray reflectometry,and grazing incidence scattering techniques. Comprehensive overviews,as well as promises and challenges, of these techniques when used operando on battery interphases are discussed in detail.
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| 95. |
- Maiti, Moumita, et al.
(författare)
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Mechanistic understanding of the correlation between structure and dynamics of liquid carbonate electrolytes: impact of polarization
- 2023
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Ingår i: Physical Chemistry Chemical Physics. - 1463-9084 .- 1463-9076. ; 25:30, s. 20350-20364
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Tidskriftsartikel (refereegranskat)abstract
- Liquid electrolyte design and modelling is an essential part of the development of improved lithium ion batteries. For mixed organic carbonates (ethylene carbonate (EC) and ethyl-methyl carbonate (EMC) mixtures)-based electrolytes with LiPF6 as salt, we have compared a polarizable force field with the standard non-polarizable force field with and without charge rescaling to model the structural and dynamic properties. The result of our molecular dynamics simulations shows that both polarizable and non-polarizable force fields have similar structural factors, which are also in agreement with X-ray diffraction experimental results. In contrast, structural differences are observed for the lithium neighborhood, while the lithium-anion neighbourhood is much more pronounced for the polarizable force field. Comparison of EC/EMC coordination statistics with Fourier transformed infrared spectroscopy (FTIR) shows the best agreement for the polarizable force field. Also for transport quantities such as ionic conductivities, transference numbers, and viscosities, the agreement with the polarizable force field is by far better for a large range of salt concentrations and EC : EMC ratios. In contrast, for the non-polarizable variants, the dynamics are largely underestimated. The excellent performance of the polarizable force field is explored in different ways to pave the way to a realistic description of the structure-dynamics relationships for a wide range of salt and solvent compositions for this standard electrolyte. In particular, we can characterize the distinct correlation terms between like and unlike ions, relate them to structural properties, and explore to which degree the transport in this electrolyte is mass or charge limited.
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| 96. |
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| 97. |
- Manuel, J., et al.
(författare)
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Electrochemical properties of lithium polymer batteries with doped polyaniline as cathode material
- 2012
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Ingår i: Materials Research Bulletin. - : Elsevier BV. - 0025-5408. ; 47:10, s. 2815-2818
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Konferensbidrag (refereegranskat)abstract
- Polyaniline (PAN!) was doped with different lithium salts such as LiPFG and LiClO4 and evaluated as cathode-active material for application in room-temperature lithium batteries. The doped PANT was characterized by FTIR and XPS measurements. In the FTIR spectra, the characteristic peaks of PANT are shifted to lower bands as a consequence of doping, and it is more shifted in the case of PANI doped with LiPFG. The cathodes prepared using PANT doped with LiPF6 and LiClO4 delivered initial discharge capacities of 125 mAh g(-1) and 112 mAh g(-1) and stable reversible capacities of 114 mAh g(-1) and 81 mAh g(-1), respectively, after 10 charge-discharge cycles. The cells were also tested using polymer electrolyte, which delivered highest discharge capacities of 142.6 mAh g(-1) and 140 mAh g(-1) and stable reversible capacities of 117 mAh g(-1) and 122 mAh g(-1) for PANT-LiPF6 and PANI-LiClO4, respectively, after 10 cycles. The cathode prepared with LiPFG doped PANT shows better cycling performance and stability as compared to the cathode prepared with LiClO4 doped PANT using both liquid and polymer electrolytes.
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| 98. |
- Maroni, F., et al.
(författare)
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Highly Stable Fe3O4/C Composite: A Candidate Material for All Solid-State Lithium-Ion Batteries
- 2020
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 1945-7111 .- 0013-4651. ; 167:7
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Tidskriftsartikel (refereegranskat)abstract
- Fe3O4 nanoparticles synthesized by a base catalyzed method are tested in an All-Solid-State (ASLB) battery using a sulfide electrolyte. The pristine nanoparticles were morphologically characterized showing an average size of 12 nm. The evaluation of the electrochemical properties shows high specific capacity values of 506 mAhg(-1) after 350 cycles at a specific current of 250 mAg(-1), with very high stability and coulombic efficiency. (C) 2020 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited.
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| 99. |
- Maroni, Fabio, et al.
(författare)
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V2O5 Cryogel: A Versatile Electrode for All Solid State Lithium Batteries
- 2019
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 1945-7111 .- 0013-4651. ; 166:16, s. A3927-A3931
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Tidskriftsartikel (refereegranskat)abstract
- All solid-state lithium batteries (ASLB) are paving the attention of the battery community due to the possibility of improving safety at good energy level. Their future development requires the investigation of new electrodes chemistries both based on intercalation or conversion mechanism. In this work we report on the synthesis and characterization of a V2O5 cryogel electrode and its application in ASLB. The combination of V2O5 cryogel and a solid-state electrolyte shows appealing properties of high capacity and enhanced safety.
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| 100. |
- Martinelli, Anna, 1978, et al.
(författare)
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A structural study on ionic-liquid-based polymer electrolyte membranes
- 2007
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 1945-7111 .- 0013-4651. ; 154:8, s. G183-G187
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated novel proton conducting membranes synthesized through the gelification of poly(vinylidene fluoride-co-hexafluoropropylene) in aprotic ionic liquids. Mobile protons were introduced by doping the system with the strong bis(trifluoromethanesulfonyl)imide acid (HTFSI), which is chemically compatible with the ionic liquids through the common TFSI- anion. The obtained membranes are thermally stable up to 115°C set by the melting of the polymer phase. At this temperature, the conductivity is on the order of 10-2 S cm-1. Raman and infrared spectroscopy show no chemical interactions between the components, indicating that the bulklike nature of the doped ionic liquids preserved within the membrane, as is the thermal stability and the high conductivity. © 2007 The Electrochemical Society.
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