| 141. |
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| 142. |
- Plylahan, Nareerat, 1984, et al.
(författare)
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Ionic liquid and hybrid ionic liquid/organic electrolytes for high temperature lithium-ion battery application
- 2016
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686. ; 216, s. 24-34
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Tidskriftsartikel (refereegranskat)abstract
- Ionic liquid (IL) and hybrid IL/organic electrolytes with pyrrolidinium cation based ILs have been investigated for application in high temperature lithium-ion batteries (HT-LIBs). The IL based electrolytes show high thermal stabilities, up to 340 degrees C, ionic conductivities of > 5 x 10(-3) S cm(-1) at 80 degrees C, and broad electrochemical stability windows: 0-5 V vs. Li+/Li degrees. The performance of LiFePO4 based half-cells at 80 degrees C is promising, delivering ca. 160 mAh g(-1) at 1C, with a rate capability up to 4C and ca. 98% coulombic efficiency. The creation of hybrid IL/organic electrolytes by adding different organic cyclic carbonate solvents reduces viscosity of the electrolytes by 28% at 80 degrees C, thereby improving the ion transport, and further improves the electrochemical performance; higher stability, better rate capability, and >= 99% coulombic efficiency. Overall, the electrolytes proposed have a potential to be applied in HT-LIBs, a concept with large advantages at the vehicle system level. (C) 2016 Elsevier Ltd. All rights reserved.
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| 143. |
- Raghavan, P., et al.
(författare)
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Electrochemical characterization of poly(vinylidene fluoride-co-hexafluoro propylene) based electrospun gel polymer electrolytes incorporating moth temperature ionic liquids as green electrolytes for lithium batteries
- 2014
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Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738. ; 262, s. 77-82
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Tidskriftsartikel (refereegranskat)abstract
- A series of gel polymer electrolytes (GPEs) based on electrospun membranes of poly(vinylidene fluoride-co-hexafluoropropylene) [P(VdF-co-HFP)] incorporating room temperature ionic liquids (RTILs), 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide complexed with lithium bis(trifluoromethylsulfonyl) inside (LiTFSI) as electrolytes have been prepared and their fundamental electrochemical properties were investigated. The morphology of electrospun membranes was examined by a field emission scanning electron microscope (FE-SEM). The membranes show uniform morphology with an average fiber diameter of 780 nm, high porosity and high electrolyte uptake. GPEs were prepared by soaking the electrospun membranes in 1 M LiTFSI in RTILs for 1 h and exhibit a high ionic conductivity of 2.4 x 10(-3)-4.5 x 10(-3) S cm(-1) at 25 degrees C. A Li/GPEs/LiFePO4 cell using these RTILs delivers high discharge capacity (similar to 140 mAh g(-1)) when evaluated at 25 degrees C at 0.1 C-rate and exhibits a very stable discharge capacity under continuous cycling. Among the GPEs, EMITFSI shows the highest electrochemical properties although the solid electrolyte interface (SEI) layer was not formed.
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| 144. |
- Rizell, Josef, 1996, et al.
(författare)
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Electrochemical Signatures of Potassium Plating and Stripping
- 2024
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Ingår i: Journal of the Electrochemical Society. - 1945-7111 .- 0013-4651. ; 171:2
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Tidskriftsartikel (refereegranskat)abstract
- Alkali metal anodes can enable unmatched energy densities in next generation batteries but suffer from insufficient coulombic efficiencies. To deduce details about processes taking place during galvanostatic cycling, voltage profiles are commonly analyzed, however the interpretation is not straightforward as multiple processes can occur simultaneously. Here we provide a route to disentangle and interpret features of the voltage profile in order to build a mechanistic understanding on alkali metal stripping and deposition, by investigating potassium metal deposition as a model case where processes and reactions are exaggerated due to the high reactivity of potassium. In particular, the importance of separating SEI formation and nucleation to correctly estimate the energy barrier for nucleation is demonstrated. Further, we show how the native layer formed on alkali metal foils gives rise to strong features in the voltage profile and propose forming alkali metal electrode through electrodeposition to mitigate these effects.
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| 145. |
- 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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| 146. |
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| 147. |
- Sadd, Matthew, 1994, et al.
(författare)
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Investigating microstructure evolution of lithium metal during plating and stripping via operando X-ray tomographic microscopy
- 2023
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- Efficient lithium metal stripping and plating operation capable of maintaining electronic and ionic conductivity is crucial to develop safe lithium metal batteries. However, monitoring lithium metal microstructure evolution during cell cycling is challenging. Here, we report the development of an operando synchrotron X-ray tomographic microscopy method capable of probing in real-time the formation, growth, and dissolution of Li microstructures during the cycling of a Li||Cu cell containing a standard non-aqueous liquid electrolyte solution. The analyses of the operando X-ray tomographic microscopy measurements enable tracking the evolution of deposited Li metal as a function of time and applied current density and distinguishing the formation of electrochemically inactive Li from the active bulk of Li microstructures. Furthermore, in-depth analyses of the Li microstructures shed some light on the structural connectivity of deposited Li at different current densities as well as the formation mechanism of fast-growing fractal Li microstructures, which are ultimately responsible for cell failure.
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| 148. |
- Sadd, Matthew, 1994, et al.
(författare)
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Polysulfide Speciation and Migration in Catholyte Lithium−Sulfur Cells
- 2022
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Ingår i: ChemPhysChem. - : Wiley. - 1439-7641 .- 1439-4235. ; 23:4
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Tidskriftsartikel (refereegranskat)abstract
- Semi-liquid catholyte Lithium−Sulfur (Li−S) cells have shown to be a promising path to realize high energy density energy storage devices. In general, Li−S cells rely on the conversion of elemental sulfur to soluble polysulfide species. In the case of catholyte cells, the active material is added through polysulfide species dissolved in the electrolyte. Herein, we use operando Raman spectroscopy to track the speciation and migration of polysulfides in the catholyte to shed light on the processes taking place. Combined with ex-situ surface and electrochemical analysis we show that the migration of polysulfides is central in order to maximize the performance in terms of capacity (active material utilization) as well as interphase stability on the Li-metal anode during cycling. More specifically we show that using a catholyte where the polysulfides have the dual roles of active material and conducting species, e. g. no traditional Li-salt (such as LiTFSI) is present, results in a higher mobility and faster migration of polysulfides. We also reveal how the formation of long chain polysulfides in the catholyte is delayed during charge as a result of rapid formation and migration of shorter chain species, beneficial for reaching higher capacities. However, the depletion of ionic species during the last stage of charge, due to the conversion to and precipitation of elemental sulfur on the cathode support, results in polarization of the cell before full conversion can be achieved.
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| 149. |
- Sadd, Matthew, 1994, et al.
(författare)
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Visualization of Dissolution‐Precipitation Processes in Lithium–Sulfur Batteries
- 2022
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Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6840 .- 1614-6832. ; 12:10
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Tidskriftsartikel (refereegranskat)abstract
- In this work, light is shed on the dissolution and precipitation processes S8 and Li2S, and their role in the utilization of active material in Li-S batteries. Combining operando X-ray Tomographic Microscopy and optical image analysis, in real-time; sulfur conversion/dissolution in the cathode, the diffusion of polysulfides in the bulk electrolyte, and the redeposition of the product of the electrochemical reaction, Li2S, on the cathode are followed. Using a custom-designed capillary cell, positioning the entire cathode volume within the field of view, the conversion of elemental sulfur to soluble polysulfides during discharge is quantitatively followed. The results show the full utilization of elemental sulfur in the cathode in the initial stage of discharge, with all solid sulfur converted to soluble polysulfide species. Optical image analysis shows a rapid diffusion of polysulfides as they migrate from the cathode to the bulk electrolyte at the start of discharge and back to the cathode in the later stages of discharge, with the formation and precipitation of Li2S. The results point to the redeposition of Li2S on all available surfaces in the cathode forming a continuous insulating layer, leaving polysulfide species remaining in the electrolyte, and this is the process limiting the cell's specific capacity.
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| 150. |
- Schantz Zackrisson, Anna, 1973, et al.
(författare)
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Concentration effects on irreversible colloid cluster aggregation and gelation of silica dispersions.
- 2006
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Ingår i: Journal of colloid and interface science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 301:1, s. 137-44
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Tidskriftsartikel (refereegranskat)abstract
- Effects of particle concentration on the irreversible aggregation of colloidal silica are studied using in situ destabilization via the ionic strength increase derived from the enzymatic hydrolysis of urea by urease. Aggregation is monitored by time-resolved optical density and dynamic light scattering measurements. It terminates at a gel boundary, signaled by a prominent increase of the optical density and incipient non-ergodicity. Raman scattering is used to demonstrate that the enzymatic reaction continues, well beyond gelation for the compositions studied here, until the urea is consumed. Calibration of the ionic conductivity permits for constructing stability diagrams in terms of particle and salt concentration. As with reversible gelation, the process exhibits a collective character in that lower ionic strengths are required for gelation of concentrated dispersions and vice versa. However, light scattering demonstrates that the gel boundary is preceded here by a line marking the transition from reversible to irreversible cluster formation, with the two transition boundaries tracking each other. Comparisons are made with dispersions destabilized by direct addition of salt solutions, which gel under very different conditions.
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