| 1. |
- Hosseini Bab Anari, Elham, 1982, et al.
(författare)
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Fluorine-free salts for aqueous lithium-ion and sodium-ion battery electrolytes
- 2016
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 6:88, s. 6, 85194-85201
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Tidskriftsartikel (refereegranskat)abstract
- A first generation of fluorine-free lithium and sodium salts based on the concept of pseudo-delocalized anions has been synthesized with both high purity and yield using water as the solvent in the reaction medium. The salts have been fully characterized by Raman and FT-IR spectroscopies, thermogravimetry, and X-ray crystallography to reveal both basic properties in terms of thermal stability and solubility as well as the local, mainly ion–ion interaction dictated, coordination details and by ionic conductivity and electrochemical stability window measurements as aqueous electrolytes. Together a picture is created of the salts' promise as components in electrolytes – primarily aiming at application in low voltage fluorinefree aqueous lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs).
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| 2. |
- Mandai, Toshihiko, 1984, et al.
(författare)
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Al conductive haloaluminate-free non-aqueous room-temperature electrolytes
- 2015
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 3:23, s. 12230-12239
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Tidskriftsartikel (refereegranskat)abstract
- Al batteries are yet rather unexplored as a promising technology to respond to the growing electrochemical energy storage demands. Despite the outstanding electrochemical activity of haloaluminate-based electrolytes, no prospect of practical re-chargeable Al batteries has yet materialized, partly due to these electrolytes' extremely sensitive nature. Hence alternative aluminum conducting electrolytes with sufficient stability are strongly needed. Here a series of room-temperature ternary electrolytes consisting of aluminum trifluoromethanesulfonate (Al[TfO]3), N-methylacetamide (NMA), and urea are presented, which provide excellent ionic conductivities by selecting appropriate ratios. Compared to conventional organic electrolytes, unprecedented solvation ability for Al-salts and remarkable ion transport properties were observed. For the optimized composition, Al[TfO]3/NMA/urea = 0.05/0.76/0.19, physicochemical properties and vibrational spectroscopy data imply a decoupling of the Al conduction mechanism from viscosity limitations and furthermore that the dissociation state of the Al[TfO]3 salt drastically changes. These phenomena are likely due to the unique coordination environment of the Al3+ ions and the multiple functions of urea in these ternary mixtures. The electrochemical properties of the optimized ternary electrolyte were studied with respect to the electrochemical stability window and using cyclic voltammetry.
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| 3. |
- Mandai, Toshihiko, 1984, et al.
(författare)
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Effect of ionic size on solvate stability of glyme-based solvate ionic liquids
- 2015
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 119:4, s. 1523-1534
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Tidskriftsartikel (refereegranskat)abstract
- A series of binary mixtures composed of glymes (triglyme, G3; tetraglyme, G4; pentaglyme, G5) and alkali-metal bis(trifluoromethanesulfonyl)amide salts (M[TFSA]; M = Li, Na, and K) were prepared, and the correlation between the composition and solvate stability was systematically investigated. Their phase diagrams and Raman spectra suggested complexation of the glymes with M[TFSA] in 1:1 and/or 2:1 molar ratio(s). From isothermal stability measurements, it was found that the formation of structurally stable complexes in the solid state did not necessarily ensure their thermal stability in the liquid state, especially in the case of 2:1 complexes, where uncoordinating or highly exchangeable glyme ligands existed in the molten complexes. The phase-state-dependent Raman spectra also supported the presence of free glymes in certain liquid complexes. The effect of the electric field induced by the alkali-metal cations on the oxidative stability of certain glyme complexes was examined by linear sweep voltammetry and quantum chemical calculations. Although the actual oxidative stability of complexes did not necessarily reflect the calculated HOMO energy levels of the glymes, the strong electric field induced by the smaller M+ cations and proper coordination structures impart high stability to the glyme complexes. The results of thermogravimetry of complexes with different M+ cations revealed that a balance of competitive interactions of the M+ ions with the glymes and [TFSA]- anions predominates the thermal stability. (Chemical Equation Presented).
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| 4. |
- Mandai, Toshihiko, 1984, et al.
(författare)
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Extraordinary aluminum coordination in a novel homometallic double complex salt
- 2015
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 44:25, s. 11259-11263
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Tidskriftsartikel (refereegranskat)abstract
- We have characterized a novel aluminum-based homometallic double complex salt, incorporating discrete octa-coordinated cationic [Al(G3)(2)](3+) and hexa-coordinated anionic [Al(TfO)(4)(OH)(2)](3-) complexes (G3 = triglyme, TfO = trifluoromethanesulfonate). X-ray crystallography, Raman spectra, and DFT calculations demonstrate extraordinary weak Al3+ coordination in [Al(G3)(2)](3+).
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| 5. |
- Mandai, Toshihiko, 1984, et al.
(författare)
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Haloaluminate-Free Cationic Aluminum Complexes: Structural Characterization and Physicochemical Properties
- 2016
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 120:38, s. 21285-21292
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Tidskriftsartikel (refereegranskat)abstract
- The large electrochemical activities of haloaluminate anions [AlnX3n+1](-), anionic complexes derived from AlX3 and Lewis basic fertilizers, have significantly contributed to the development of industrial coatings and more recently also to eledrochernical energy storage. In contrast, cationic metal complexes have just emerged as a class of species interesting as multivalent main charge carriers for Mg, Ca, and especially here Al batteries. Despite the potential of such complexes to efficiently deliver Al3+ cations at the electrode! electrolyte interfaces, very few cationic aluminum complexes that do not contain moisture sensitive [AlnX3n+1](-) counter anions have been reported due to the few, and difficult to synthesize, commercially available parent aluminum salts. Here a range of cationic aluminum complexes with different ligands and, anionic structures were successfully synthesized by complexation of AlCl3 with certain ligands to create fully solvated [Al(L)(6)]Cl-3 complexes and subsequent application of anion metathesis reactions. X-ray crystallography aided by vibrational spectroscopy corroborates the formation of discrete complexes with hexacoordinated octahedral Al3+ cations balanced by three isolated anions. The resulting physicochemical properties are strongly dependent on the constituent ions, and one special choice of ligand and anion results in a, novel design of a room temperature quasi-ionic liquid having high ionic conductivity. Although the high-melting complexes with DMSO ligands are inactive, the:molten complex exhibits both cathodic and anodic currents. This is the first electrolyte that allows quasi-reversible electrochemical plating/stripping of Al metal without any fragile anion being present.
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| 6. |
- Mandai, Toshihiko, 1984, et al.
(författare)
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Pentaglyme-K salt binary mixtures: phase behavior, solvate structures, and physicochemical properties
- 2015
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 17:4, s. 2838-2849
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Tidskriftsartikel (refereegranskat)abstract
- We prepared a series of binary mixtures composed of certain K salts (KX) and pentaglyme (G5) with different salt concentrations and anionic species ([X](-) : [(CF3SO2)(2)N](-) = [TFSA](-), [CF3SO3](-) = [TfO](-), [C4F9SO3](-) = [NfO](-), PF6-, SCN-), and characterized them with respect to their phase diagrams, solvate structures, and physicochemical properties. Their phase diagrams and thermal stability strongly implied the formation of equimolar complexes. Single-crystal X-ray crystallography was performed on certain equimolar complexes, which revealed that G5 molecules coordinate to K+ cations in a characteristic manner, like 18-crown-6 ether in the crystalline state, irrespective of the paired anions. The solvate structures in the molten state were elucidated by a combination of temperature-dependent Raman spectroscopy and X-ray crystallography. A drastic spectral variation was observed in the [K(G5)(1)][TfO] Raman spectra, indicating that solvate structures in the crystalline state break apart upon melting. The solvate stability of [K(G5)(1)]X is closely related to the ion-ion interaction of the parent salts. A stable solvate forms when the ion-dipole interaction between K+ and G5 overwhelms the ion-ion interaction between K+ and X-. Furthermore, the physicochemical properties of certain equimolar mixtures were evaluated. A Walden plot clearly reflects the ionic nature of the molten equimolar complexes. Judging from the structural characteristics and dissociativity, we classified [K(G5)(1)]X into two groups, good and poor solvate ionic liquids.
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| 7. |
- Terada, S., et al.
(författare)
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Thermal and Electrochemical Stability of Tetraglyme-Magnesium Bis(trifluoromethanesulfonyl)amide Complex: Electric Field Effect of Divalent Cation on Solvate Stability
- 2016
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 120:3, s. 1353-1365
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Tidskriftsartikel (refereegranskat)abstract
- Phase behavior of binary mixtures of tetraglyme (G4) and Mg[TFSA]2 (TFSA: bis(trifluoromethanesulfonyl)amide) was investigated. In a 1:1 molar ratio, G4 and Mg[TFSA]2 formed a stable complex with a melting point of 137 degrees C. X-ray crystallography of a single crystal of the complex grown from a G4-Mg[TFSA]2 binary mixture revealed that the G4 molecule wraps around Mg2+ to form a complex [Mg(G4)](2+) cation, and the two [TFSA](-) anions also participate in the Mg2+ coordination in the crystal. The thermal stability of [Mg(G4)][TFSA](2) was examined by thermogravimetry, and it was found that the complex is stable up to 250 degrees C. Above 250 degrees C, desolvation of the Mg2+ ion takes place and G4 evaporates. On the other hand, the weight loss starts at around 140 degrees C in solutions containing excess G4 (n > 1 in Mg[TFSA]2:G4 = 1:n) due to the evaporation of free (uncoordinated) G4. The suppression of G4 volatility in the [Mg(G4)][TFSA]2 complex is attributed to strong electrostatic and induction interactions between divalent Mg2+ and G4. In addition, complexation of G4 with Mg2+ is effective in enhancing the oxidative stability of G4. Linear sweep voltammetry revealed that the oxidative decomposition of [Mg(G4)][TFSA]2 occurs at electrode potentials >5 V vs Li/Li+, while the oxidation of uncoordinated G4 occurs at around 4.0 V. This oxidative stability enhancement occurs because the HOMO energy level of G4 is reduced by complexation with Mg2+, which is supported by the ab initio calculations.
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| 8. |
- Zhang, Chao, et al.
(författare)
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2023 Roadmap on molecular modelling of electrochemical energy materials
- 2023
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Ingår i: Journal of Physics. - : Institute of Physics Publishing (IOPP). - 2515-7655. ; 5:4
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Tidskriftsartikel (refereegranskat)abstract
- New materials for electrochemical energy storage and conversion are the key to the electrification and sustainable development of our modern societies. Molecular modelling based on the principles of quantum mechanics and statistical mechanics as well as empowered by machine learning techniques can help us to understand, control and design electrochemical energy materials at atomistic precision. Therefore, this roadmap, which is a collection of authoritative opinions, serves as a gateway for both the experts and the beginners to have a quick overview of the current status and corresponding challenges in molecular modelling of electrochemical energy materials for batteries, supercapacitors, CO2 reduction reaction, and fuel cell applications.
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