| 1. |
- Forero-Saboya, Juan, et al.
(författare)
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Cation Solvation and Physicochemical Properties of Ca Battery Electrolytes
- 2019
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 123:59, s. 29524-29532
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Tidskriftsartikel (refereegranskat)abstract
- Divalent-cation-based batteries are being considered as potential high energy density storage devices. The optimization of electrolytes for these technologies is, however, still largely lacking. Recent demonstration of the feasibility of Ca and Mg plating and stripping in the presence of a passivation layer or an artificial interphase has paved the way for more diverse electrolyte formulations. Here, we exhaustively evaluate several Ca-based electrolytes with different salts, solvents, and concentrations, via measuring physicochemical properties and using vibrational spectroscopy. Some comparisons with Mg- and Li-based electrolytes are made to highlight the unique properties of the Ca2+ cation. The Ca-salt solubility is found to be a major issue, calling for development of new highly dissociative salts. Nonetheless, reasonable salt solubility and dissociation are achieved using bis(trifluoromethanesulfonyl)imide (TFSI), BF4, and triflate anion based electrolytes and high-permittivity solvents, such as ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (gBL), and N,N-dimethylformamide (DMF). The local Ca2+ coordination is concentration-dependent and rather complex, possibly involving bidentate coordination and participation of the nitrogen atom of DMF. The ionicity and the degree of ion-pair formation are both investigated and found to be strongly dependent on the nature of the cation, solvent donicity, and salt concentration. The large ion-ion interaction energies of the contact ion pairs, confirmed by density functional theory (DFT) calculations, are expected to play a major role in the interfacial processes, and thus, we here provide electrolyte design strategies to engineer the cation solvation and possibly improve the power performance of divalent battery systems.
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| 2. |
- Monti, Damien, 1986
(författare)
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Innovative Electrolytes and Electrodes for Sodium-Ion Batteries
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Batteries are expected to be masterpieces for future large-scale energy storage, but the emergence of ecological and financial concerns has forced us to think about complementary battery technologies to the today outstanding lithium-ion batteries (LIBs). Therefore, the sodium-ion battery (SIB) is a concept worth studying - especially for large-scale applications due to the abundance of sodium as an element, the overall low cost anticipated, and the similarities with LiBs, which should ease a technology change. SIB electrolytes can be based for example on organic solvents or ionic liquids (IL), both doped with the appropriate sodium salt. Several features and properties of IL-based electrolytes for SIBs are investigated in this thesis; the ionic conductivity of novel electrolytes chosen among the large number of IL available, complemented by Raman vibrational spectroscopy to understand the interaction within the electrolyte and the possible operation temperature range by differential scanning calorimetry. In addition, a significant part of the work is dedicated to the electrochemical compatibility of the electrolytes with SIB electrode materials. The stability and behaviour toward the electrodes are investigated to make possible a fully operative safer SIB in the future, possibly based on IL based electrolytes.
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| 3. |
- Monti, Damien, 1986
(författare)
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Innovative Electrolytes for Safer Sodium-Ion Batteries
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The overconsumption of non-renewable/fossil fuels by vehicles and industry has resulted in dangerously high levels of CO2 in the atmosphere the last 40 years. The impact on the environment, climate and public health urge governments to find new technologies to ensure a sustainable development. In this context, the development of greener energy storage technologies such as novel secondary batteries has already had a wide impact. The commercialisation of the first lithium-ion battery (LIB) in 1991 by Sony has revolutionized mobile devices and the LIB now emerges in electric vehicles, but can be even more important for load levelling of renewable energy. Unfortunately, an increase in our lithium consumption coupled with its low abundance in the Earth’s crust raises financial and sustainability concerns, forcing us to think about complementary battery technologies. One of the most appealing alternatives is to use sodium instead of lithium. Chemically these elements are close and these similarities should ease a technological change. Therefore, the sodium-ion battery (SIB) is a concept worth studying - especially for large-scale applications due to the “unlimited” abundance of sodium in the Earth’s crust and the overall low materials cost, anticipated to be 30 times lower than for Li.Electrolytes for SIBs can be based on organic solvents or ionic liquids (IL), or a mixture of both as matrices, all doped with the appropriate sodium salt. Several features and properties of hybrid IL and pure IL-based electrolytes for SIBs are investigated in this thesis; the ionic conductivity of novel electrolytes using a few ILs chosen among the large number available. These studies are complemented by Raman vibrational spectroscopy to understand the interactions within the electrolytes, and the possible operation temperature ranges by differential scanning calorimetry. Moreover, several electrolytes have been analysed to understand the IL contribution to various safety measures; ignition time (IT), flash point (FP), and self-extinguishing time (SET).In addition, a significant part of the work is dedicated to the electrochemical compatibility of the electrolytes with novel SIB electrode materials. The stability and behaviour toward the electrodes are investigated to make possible a fully operative safer SIB in the future, possibly based on hybrid IL or pure IL-based electrolytes.
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| 4. |
- Monti, Damien, 1986, et al.
(författare)
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Ionic liquid based electrolytes for sodium-ion batteries: Na+ solvation and ionic conductivity
- 2014
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 245, s. 630-636
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Tidskriftsartikel (refereegranskat)abstract
- Ionic liquid (IL) based sodium-ion (Na+) battery electrolytes obtained by mixing imidazolium-TFSI ILs (EMIm-TFSI and BMIm-TFSI) with the corresponding sodium salt (NaTFSI) have been investigated using a wide range of characterization techniques: dielectric spectroscopy, differential scanning calorimetry, densitometry, viscometry, and Raman spectroscopy. The sodium ion conducting electrolytes exhibit excellent ionic conductivities, up to 5.5 mS cm(-1) at room temperature, and a useful thermal window of -86 degrees C to 150 degrees C. In more detail, Raman data analysis supported by DFT calculations on Na+-TFSI complexes, allow us to determine the sodium ion solvation and charge carrier nature as a function of salt concentration. The results are compared to data for the corresponding Li systems and while such electrolytes essentially form [Li(TFSI)(2)](-) as the main Li+ carrier, the sodium systems seem to dominantly form [Na(TFSI)(3)](2-) complexes. The effects on conductivity and viscosity and the consequences for sodium-ion battery implementation are discussed. (C) 2013 Elsevier B.V. All rights reserved.
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| 5. |
- Monti, Damien, 1986, et al.
(författare)
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Microwaves as a synthetic route for preparing electrochemically active TiO2 nanoparticles
- 2013
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Ingår i: Journal of Materials Research. - : Springer Science and Business Media LLC. - 0884-2914 .- 2044-5326. ; 28:3, s. 340-347
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Tidskriftsartikel (refereegranskat)abstract
- Nanocrystalline anatase was synthesized, using both domestic and laboratory microwave ovens, from different precursors. Nanoparticulate anatase was obtained after microwave irradiation of tetra-butyl orthotitanate solution in benzyl alcohol. As-synthesized samples have orange color due to the presence of organics that were eliminated after annealing at 500 degrees C, whereas the size of small anatase nanocrystals (around 8 nm) was preserved. Other nanocrystalline anatase samples were obtained from hexafluorotitanate-organic salt ionic liquid-like precursors. In this case, use of a domestic microwave oven and very short processing times (1-3 min irradiation time) were involved. Good specific capacity values and capacity retention at high C rates for insertion/deinsertion of Li+ were recorded when testing such nanoparticles as electrode material in lithium cells. The electrochemical performances were found be strongly dependent on the phase composition, which in turn could be tuned through the synthetic procedure.
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| 6. |
- Monti, Damien, et al.
(författare)
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Multivalent Batteries-Prospects for High Energy Density: Ca Batteries
- 2019
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Ingår i: Frontiers in Chemistry. - : Frontiers Media SA. - 2296-2646. ; 7:FEB
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Tidskriftsartikel (refereegranskat)abstract
- Batteries based on Ca hold the promise to leapfrog ahead regarding increases in energy densities and are especially attractive as Ca is the 5th most abundant element in the Earth's crust. The viability of Ca metal anodes has recently been shown by approaches that either use wide potential window electrolytes at moderately elevated temperatures or THE-based electrolytes at room temperature. This paper provides realistic estimates of the practical energy densities for Ca-based rechargeable batteries at the cell level, calculated using open source models for several concepts. The results from the Ca metal anode batteries indicate that doubled or even tripled energy density as compared to the state-of-the-art Li-ion batteries is viable if a practical proof-of-concept can be achieved.
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| 7. |
- Monti, Damien, 1986, et al.
(författare)
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Towards safer sodium-ion batteries via organic solvent/ionic liquid based hybrid electrolytes
- 2016
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 324, s. 712-721
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid electrolytes aimed at application in sodium-ion batteries (SIB) consisting of an organic solvent mixture (EC:PC) and different ionic liquids (ILs); EMImTFSI, BMImTFSI, and Pyr13TFSI, and with the NaTFSI salt providing the Na+ charge carriers have here been extensively studied. The physico-chemical and electrochemical characterisation includes ionic conductivity, viscosity, density, cation coordination and solvation, various safety measures, and electrochemical stability window (ESW). Hybrid electrolytes with 10-50% of IL content were found to have ionic conductivities on par with comparable organic solvent based electrolytes, but with highly enhanced safety properties. A systematic Raman spectroscopy study of the cation coordination and solvation before and after electrolyte safety tests by ignition suggest that IL cations and TFSI remain stable when ignited while organic solvents are consumed. Finally, the solid electrolyte interphase (SEI) formed when using hybrid electrolytes has both better mechanical and electrochemical stability than the SEI derived from pure IL based electrolytes. For a half-cell with a hard carbon (HC) electrode and a hybrid electrolyte with a composition of 0.8 m NaTFSI in EC0.45:PC0.45:Pyr13TFSI0.10 encouraging results were obtained for IL based electrolytes - ca. 182 mAhg-1 at C/10 over 40 cycles.
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| 8. |
- Monti, Damien, 1986, et al.
(författare)
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Towards standard electrolytes for sodium-ion batteries: physical properties, ion solvation and ion-pairing in alkyl carbonate solvents
- 2020
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 22:39, s. 22768-22777
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Tidskriftsartikel (refereegranskat)abstract
- The currently emerging sodium-ion battery technology is in need of an optimized standard organic solvent electrolyte based on solid and directly comparable data. With this aim we have made a systematic study of "simple"electrolyte systems consisting of two sodium salts (NaTFSI and NaPF6) dissolved in three different alkyl carbonate solvents (EC, PC, DMC) within a wide range of salt concentrations and investigated: (i) their more macroscopic physico-chemical properties such as ionic conductivity, viscosity, thermal stability, and (ii) the molecular level properties such as ion-pairing and solvation. From this all electrolytes were found to have useful thermal operational windows and electrochemical stability windows, allowing for large scale energy storage technologies focused on load levelling or (to a less extent) electric vehicles, and ionic conductivities on par with analogous lithium-ion battery electrolytes, giving promise to also be power performant. Furthermore, at the molecular level the NaPF6-based electrolytes are more dissociated than the NaTFSI-based ones because of the higher ionic association strength of TFSI compared to PF6- while two different conformers of DMC participate in the Na+ first solvation shells-a Na+ affected conformational equilibrium and induced polarity of DMC. The non-negligible presence of DMC in the Na+ first solvation shells increases as a function of salt concentration. Overall, these results should both have a general impact on the design of more performant Na-conducting electrolytes and provide useful insight on the very details of the importance of DMC conformers in any cation solvation studies.
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| 9. |
- Ponrouch, A., et al.
(författare)
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Non-Aqueous Electrolytes for Sodium-Ion Batteries
- 2015
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 1364-5501 .- 0959-9428 .- 2050-7488 .- 2050-7496. ; 3:1, s. 22-42
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Forskningsöversikt (refereegranskat)abstract
- The first review of the various electrolytes currently used and developed for sodium-ion batteries (SIBs), both in terms of materials and concepts, is presented. In contrast to the Li-ion battery (LIB), which is a mature technology for which a more or less unanimously accepted "standard electrolyte" exists: 1 M LiPF6 in EC/DMC, the electrolyte of choice for SIBs has not yet fully conformed to a standard. This is true for both materials: salts, solvents, or additives, and concept, using the main track of organic solvents or aiming for other concepts. SIB research currently prospers, benefitting from using know-how gained from 30 years of LIB R&D. Here the currently employed electrolytes are emphasized and their effects on practical SIB performance are outlined, scrutinizing the rationale for specific choices made, salts, solvents, additives, concentrations, etc. for each specific cell set-up and usage conditions.
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| 10. |
- Ponrouch, A., et al.
(författare)
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Towards high energy density sodium ion batteries through electrolyte optimization
- 2013
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Ingår i: Energy and Environmental Sciences. - : Royal Society of Chemistry (RSC). - 1754-5692 .- 1754-5706. ; 6:8, s. 2361-2369
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Tidskriftsartikel (refereegranskat)abstract
- A comprehensive study is reported entailing optimization of sodium ion electrolyte formulation and compatibility studies with positive and negative electrode materials. EC:PC:DMC and EC:PC:DME were found to exhibit optimum ionic conductivities and lower viscosities. Yet, hard carbon negative electrode materials tested in such electrolytes exhibit significant differences in performance, rooted in the different resistivity of the SEI, which results in too large polarization and concomitant loss of capacity at low potentials when DME is used as a co-solvent. EC0.45:PC0.45:DMC0.1 was found to be the optimum composition resulting in good rate capability and high capacity upon sustained cycling for hard carbon electrodes. Its compatibility with positive Na3V2(PO4)(2)F-3 (NVPF) electrodes was also confirmed, which led to the assembly of full Na-ion cells displaying an operation voltage of 3.65 V, very low polarisation and excellent capacity retention upon cycling with ca. 97 mA h g(-1) of NVPF after more than 120 cycles together with satisfactory coulombic efficiency (>98.5%) and very good power performance. Such values lead to energy densities comparable to those of the current state-of-the-art lithium-ion technology.
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