| 1. |
- Cano, Israel, et al.
(författare)
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Blurring the boundary between homogenous and heterogeneous catalysis using palladium nanoclusters with dynamic surfaces
- 2021
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Using a magnetron sputtering approach that allows size-controlled formation of nanoclusters, we have created palladium nanoclusters that combine the features of both heterogeneous and homogeneous catalysts. Here we report the atomic structures and electronic environments of a series of metal nanoclusters in ionic liquids at different stages of formation, leading to the discovery of Pd nanoclusters with a core of ca. 2 nm surrounded by a diffuse dynamic shell of atoms in [C4C1Im][NTf2]. Comparison of the catalytic activity of Pd nanoclusters in alkene cyclopropanation reveals that the atomically dynamic surface is critically important, increasing the activity by a factor of ca. 2 when compared to compact nanoclusters of similar size. Catalyst poisoning tests using mercury and dibenzo[a,e]cyclooctene show that dynamic Pd nanoclusters maintain their catalytic activity, which demonstrate their combined features of homogeneous and heterogeneous catalysts within the same material. Additionally, kinetic studies of cyclopropanation of alkenes mediated by the dynamic Pd nanoclusters reveal an observed catalyst order of 1, underpinning the pseudo-homogeneous character of the dynamic Pd nanoclusters.
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| 2. |
- Garcia-Quintana, Laura, et al.
(författare)
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Stabilisation of the superoxide anion in bis(fluorosulfonyl)imide (FSI) ionic liquid by small chain length phosphonium cations: Voltammetric, DFT modelling and spectroscopic perspectives
- 2021
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Ingår i: Electrochemistry Communications. - : Elsevier BV. - 1388-2481. ; 127
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Tidskriftsartikel (refereegranskat)abstract
- Ionic liquids (ILs) containing the bis(fluorosulfonyl)imide anion, FSI, have been investigated as electrolytes for metal-air batteries. Full chemical reversibility is found for the reduction of oxygen to superoxide at 60 degrees C under short time scale conditions of cyclic voltammetry at a glassy carbon electrode when the IL contains the small chain length triisobutyl(methyl)phosphonium rather than a pyrrolidinium cation. DFT calculations suggest that this is a consequence of the higher ion pair association energy and shorter intermolecular distance associated with the interaction of the superoxide anion with the phosphonium cation. Stabilization on longer timescales was also established by spectroscopic techniques when the phosphonium based ILs were exposed to KO2. Studies on superoxide stability in related ionic liquids containing the triisobutyl(methyl)phosphonium cation with the fluorosulfonyl(trifluoromethanesulfonyl)imide, FTFSI, or bis(trifluoromethanesulfonyl)imide, TFSI, anions are also reported.Y
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| 3. |
- Halat, David M., et al.
(författare)
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Natural abundance solid-state S-33 NMR study of NbS3: applications for battery conversion electrodes
- 2019
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1364-548X .- 1359-7345. ; 55:84, s. 12687-12690
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Tidskriftsartikel (refereegranskat)abstract
- We report ultra-wideline, high-field natural abundance solid-state S-33 NMR spectra of the Li-ion battery conversion electrode NbS3, the first S-33 NMR study of a compound containing disulfide (S-2(2-)) units. The large quadrupolar coupling parameters (C-Q approximate to 31 MHz) are consistent with values obtained from DFT calculations, and the spectra provide evidence for the linear Peierls distortion that doubles the number of S-33 sites.
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| 4. |
- Han, S. D., et al.
(författare)
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Solvate Structures and Computational/Spectroscopic Characterization of Lithium Difluoro(oxalato)borate (LiDFOB) Electrolytes
- 2013
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 117:11, s. 5521-5531
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Tidskriftsartikel (refereegranskat)abstract
- Lithium difluoro(oxalato)borate (LiDFOB) is a relatively new salt designed for battery electrolyte usage. Limited information is currently available, however, regarding the ionic interactions of this salt (i.e., solvate formation) when it is dissolved in aprotic solvents. Vibrational spectroscopy is a particularly useful tool for identifying these interactions, but only if the vibrational bands can be correctly linked to specific forms of anion coordination. Single crystal structures of LiDFOB solvates have therefore been used to both explore the DFOB-center dot center dot center dot Li+ cation coordination interactions and serve as unambiguous models for the assignment of the Raman vibrational bands. The solvate crystal structures determined indude (monoglyme)(2):LiDFOB, (1,2-diethoxyethane)(3/2):LiDFOB, (acetonitrile)(3):LiDFOB, (acetonitrile)(1):LiDFOB, (dimethyl carbonate)(3/2):LiDFOB, (succinonitrile)(1):LiDFOB, (adiponitrile)(1):LiDFOB, (PMDETA)(1):LiDFOB, (CRYPT-222)(2/3):LiDFOB, and (propylene carbonate)(1):LiDFOB. DFT calculations have been incorporated to provide additional insight into the origin (i.e., vibrational modes) of the Raman vibrational bands to aid in the interpretation of the experimental analysis.
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| 5. |
- Jin, Yanting, et al.
(författare)
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Understanding Fluoroethylene Carbonate and Vinylene Carbonate Based Electrolytes for Si Anodes in Lithium Ion Batteries with NMR Spectroscopy
- 2018
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 140:31, s. 9854-9867
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Tidskriftsartikel (refereegranskat)abstract
- Fluoroethylene carbonate (FEC) and vinylene carbonate (VC) are widely used as electrolyte additives in lithium ion batteries. Here we analyze the solid electrolyte interphase (SEI) formed on binder-free silicon nanowire (SiNW) electrodes in pure FEC or VC electrolytes containing 1 M LiPF6by solid-state NMR with and without dynamic nuclear polarization (DNP) enhancement. We find that the polymeric SEIs formed in pure FEC or VC electrolytes consist mainly of cross-linked poly(ethylene oxide) (PEO) and aliphatic chain functionalities along with additional carbonate and carboxylate species. The formation of branched fragments is further confirmed by13C-13C correlation NMR experiments. The presence of cross-linked PEO-type polymers in FEC and VC correlates with good capacity retention and high Coulombic efficiencies of the SiNWs. Using29Si DNP NMR, we are able to probe the interfacial region between SEI and the Si surface for the first time with NMR spectroscopy. Organosiloxanes form upon cycling, confirming that some of the organic SEI is covalently bonded to the Si surface. We suggest that both the polymeric structure of the SEI and the nature of its adhesion to the redox-active materials are important for electrochemical performance.
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| 6. |
- Jonsson, Erlendur, 1983
(författare)
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Ab initio modelling of alkali-ion battery electrolyte properties
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lithium-ion batteries are omnipresent in modern electronics. They can be found in laptops, mobile phones and electric vehicles. However, there is room for both improvement, as the thermal instability of the dominant lithium salt used in batteries today, LiPF6, causes safety concerns, and more fundamental changes, as there is a limited amount of lithium available – resulting in sodium-ion batteries being a nascent field of study.This thesis looks in detail at some underlying fundamental features affecting properties ofelectrolytes of both lithium-ion and sodium-ion batteries. These properties include the oxidative stability of the anions of the lithium and sodium salts (important for voltage and safety); the cation-anion interaction strength (important for conductivity); the solvation of the lithium and sodium cations in the common carbonate solvents (important for conductivity and the (de-)solvation at the anodes/cathodes); and the thermal stability of the anions and the possible decomposition reactions (important for safety).The properties are mainly studied for a number of both novel and well established anions. Some of the novel anions involve completely new concepts for anion design for alkali-ion battery electrolytes. The systems are studied with a number of ab initio methods, most based on density functional theory (DFT).These include high level calculations of benchmark quality. The applicability of DFT and the selection of DFT functionals is also studied. Novel calculation strategies were employed to understand thermal decomposition.
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| 7. |
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| 8. |
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| 9. |
- Jonsson, Erlendur, 1983, et al.
(författare)
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Electrochemical oxidation stability of anions for modern battery electrolytes: a CBS and DFT study
- 2015
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 17:5, s. 3697-3703
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Tidskriftsartikel (refereegranskat)abstract
- The electrochemical stability vs. oxidation is a crucial property of anions in order to be suitable as components in lithium-ion batteries. Here the applicability of a number of computational approaches and methods to assess this property, employing a wide selection of DFT functionals, has been studied using the CCSD(T)/CBS method as the reference. In all, the vertical anion oxidation potential, Delta E-v, is a fair way to calculate the stability vs. oxidation, however, a functional of at least hybrid quality is recommended. In addition, the chemical hardness, eta, is identified as a novel approach to calculate the stability vs. oxidation.
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| 10. |
- Jonsson, Erlendur, 1983
(författare)
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Ionic liquids as electrolytes for energy storage applications – A modelling perspective
- 2020
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Ingår i: Energy Storage Materials. - : Elsevier BV. - 2405-8297. ; 25, s. 827-835
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Forskningsöversikt (refereegranskat)abstract
- Ionic liquids as electrolytes for energy storage devices is a promising field. Here, the various approaches of how ionic liquids can be modelled are discussed along with how the modelling connects to experimental results. Recent theoretical developments are highlighted along with extended discussion of what molecular dynamics simulation options are now available and what key results can be extracted. Ab initio work is also discussed, this includes some of the spectral properties, both of ionic liquids and their electrolyte formulations.
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| 11. |
- Jonsson, Erlendur, 1983
(författare)
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Modelling of alkali-ion battery electrolytes
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lithium-ion batteries are omnipresent in modern electronics. They can be found in laptops, mobile phones and electric vehicles. However, there is room for both improvement, as the thermal instability of the dominant lithium salt used in batteries today, LiPF6, causes safety concerns, and more conceptual changes, as there is a limited amount of lithium available - resulting in sodium-ion batteries being a nascent field of study.This thesis looks in detail at some of the phenomena found in the electrolytes of both lithium-ion and sodium-ion batteries. These properties include the oxidative stability of the anions of the lithium and sodium salts (important for voltage and safety); the cation-anion interaction strength (important for conductivity); and also the solvation of the lithium and sodium cations in the common carbonate solvents (important for conductivity and the stability vs. the anodes/cathodes).These properties are studied for a number of both novel and well established anions. Some of the novel anions involve completely new concepts for anion design for lithium battery electrolytes. The systems are studied mostly with density functional theory (DFT) calculations and a number of other ab initio methods. These include high level calculations of benchmark quality. The applicability of DFT and the selection of DFT functionals is also studied.
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| 12. |
- Jonsson, Erlendur, 1983, et al.
(författare)
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Modern battery electrolytes: Ion-ion interactions in Li+/Na+ conductors from DFT calculations
- 2012
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 14:30, s. 10774-10779
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Tidskriftsartikel (refereegranskat)abstract
- Sodium-ion batteries, the sodium counterpart of the ubiquitous lithium-ion batteries, are currently being developed as a complementary technology to assure resource availability. As battery electrolytes tend to be one of the more limiting parts of any battery for both performance and life-length, chemical and physical data on sodium-ion battery electrolytes are important for rational development. Here the cation-anion interaction, a key property of any salt used in an electrolyte, of a number of salts is probed using numerous DFT methods via the ion-pair dissociation reaction: AlkAn reversible arrow Alk(+) + An(-), where An(-) is any anion and Alk(+) is Na+ or Li+, the latter used here for a straight-forward literature and methodology comparison. Furthermore, the applicability of different DFT functionals for these types of calculations is benchmarked vs. a robust higher accuracy method (G4MP2).
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| 13. |
- Jonsson, Erlendur, 1983, et al.
(författare)
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Novel pseudo-delocalized anions for lithium battery electrolytes
- 2012
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 14:17, s. 6021-6025
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Tidskriftsartikel (refereegranskat)abstract
- A novel anion concept of pseudo-delocalized anions, anions with distinct positive and negative charge regions, has been studied by a computer aided synthesis using DFT calculations. With the aim to find safer and better performing lithium salts for lithium battery electrolytes two factors have been evaluated: the cation-anion interaction strength via the dissociation reaction LiAn (sic) Li+ + An(-) and the anion oxidative stability via a vertical ionisation from anion to radical. Based on our computational results some of these anions have shown promise to perform well as lithium salts for modern lithium batteries and should be interesting synthetic targets for future research.
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| 14. |
- Liu, Tao, et al.
(författare)
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Understanding LiOH Formation in a Li-O2 Battery with LiI and H2O Additives
- 2019
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Ingår i: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; 9:1, s. 66-77
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Tidskriftsartikel (refereegranskat)abstract
- LiI-promoted LiOH formation in Li-O2 batteries with wet ether electrolytes has been investigated by Raman, nuclear magnetic resonance spectroscopy, operando pressure tests, and molecular dynamics simulations. We find that LiOH formation is a synergistic effect involving both H2O and LiI additives, whereas with either alone Li2O2 forms. LiOH is generated via a nominal four-electron oxygen reduction reaction, the hydrogen coming from H2O and the oxygen from both O2 and H2O, and with fewer side reactions than typically associated with Li2O2 formation; the presence of fewer parasitic reactions is attributed to the proton donor role of water, which can coordinate to O2- and the higher chemical stability of LiOH. Iodide plays a catalytic role in decomposing H2O2/HO2- and thereby promoting LiOH formation, its efficacy being highly dependent on the water concentration. This iodide catalysis becomes retarded at high water contents due to the formation of large water-solvated clusters, and Li2O2 forms again.
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| 15. |
- 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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| 16. |
- 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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| 17. |
- Scheers, Johan, 1979, et al.
(författare)
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Novel Lithium Imides; Effects of -F, -CF(3), and -C N Substituents on Lithium Battery Salt Stability and Dissociation
- 2012
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Ingår i: Electrochemistry. - : The Electrochemical Society of Japan. - 1344-3542 .- 2186-2451. ; 80:1, s. 18-25
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Tidskriftsartikel (refereegranskat)abstract
- New lithium imide salts have been studied using computational chemistry methods. Intrinsic anion oxidation potentials and ion pair dissociation energies are presented for six lithium sulfonyl imides (R-O(2)S-N-SO(2)-R) and six lithium phosphoryl imides (R(2)-OP-N-PO-R(2)), as a function of -F, -CF(3), and -C N substitution. The modelled properties are used to estimate the electrochemical oxidation stability of the anions and the relative ease of charge carrier creation in lithium battery electrolytes. The results show that both properties are improved with cyano-substitution, which in part is corroborated when comparing with other classes of lithium salts. However, the comparison also shows ambiguous oxidation stability results for cyano-substituted reference salts of the type PF(x)(CN)((6) over bar -x) and BF(x)(CN)((4) over bar -x), using two different approaches - we present a tentative explanation for this. For the imide anions and PF(6)(-), the bond dissociation energy is introduced as a third property, to gauge the thermal stability of the imide anions. The results suggest that the C-S and C-P bonds are the most liable to break and that the thermal stability is inversely related to the ion pair dissociation energy. (C) The Electrochemical Society of Japan, All rights reserved.
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| 18. |
- Seo, D. M., et al.
(författare)
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Solvate Structures and Computational/Spectroscopic Characterization of LiBF4 Electrolytes
- 2014
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 118:32, s. 18377-18386
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Tidskriftsartikel (refereegranskat)abstract
- Crystal structures have been determined for both LiBF4 and HBF4 solvates: (acetonitrile)(2):LiBF4, (ethylene glycol diethyl ether)(1):LiBF4, (diethylene glycol diethyl ether)(1):LiBF4, (tetrahydrofuran)(1):LiBF4, (methyl methoxyacetate)(1):LiBF4, (succinonitrile)(1):LiBF4, (N,N,N',N '',N ''-pentamethyldiethylenetriamine)(1):HBF4, (N,N,N',N'-tetramethylethylenediamine)(3/2):HBF4, and (phenanthroline)(2):HBF4. These, as well as other known LiBF4 solvate structures, have been characterized by Raman vibrational spectroscopy to unambiguously assign the anion Raman band positions to specific forms of BF4-center dot center dot center dot Li+ cation coordination. In addition, complementary DFT calculations of BF4-center dot center dot center dot Li+ cation complexes have provided additional insight into the challenges associated with accurately interpreting the anion interactions from experimental Raman spectra. This information provides a crucial tool for the characterization of the ionic association interactions within electrolytes.
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| 19. |
- Temprano, Israel, et al.
(författare)
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Toward Reversible and Moisture-Tolerant Aprotic Lithium-Air Batteries
- 2020
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Ingår i: Joule. - : Elsevier BV. - 2542-4351. ; 4:11, s. 2501-2520
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Tidskriftsartikel (refereegranskat)abstract
- The development of moisture-tolerant, LiOH-based non-aqueous Li-O2 batteries is a promising route to bypass the inherent limitations caused by the instability of their typical discharge products, LiO2 and Li2O2. The use of the I−/I3− redox couple to mediate the LiOH-based oxygen reduction and oxidation reactions has proven challenging due to the multiple reaction paths induced by the oxidation of I− on cell charging. In this work, we introduce an ionic liquid to a glyme-based electrolyte containing LiI and water and demonstrate a reversible LiOH-based Li-O2 battery cycling that operates via a 4 e−/O2 process with a low charging overpotential (below 3.5 V versus Li/Li+). The addition of the ionic liquid increases the oxidizing power of I3−, shifting the charging mechanism from IO−/IO3− formation to O2 evolution.
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| 20. |
- Zhao, Evan Wenbo, et al.
(författare)
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In situ NMR metrology reveals reaction mechanisms in redox flow batteries
- 2020
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 579:7798, s. 224-228
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Tidskriftsartikel (refereegranskat)abstract
- Large-scale energy storage is becoming increasingly critical to balancing renewable energy production and consumption1. Organic redox flow batteries, made from inexpensive and sustainable redox-active materials, are promising storage technologies that are cheaper and less environmentally hazardous than vanadium-based batteries, but they have shorter lifetimes and lower energy density2,3. Thus, fundamental insight at the molecular level is required to improve performance4,5. Here we report two in situ nuclear magnetic resonance (NMR) methods of studying redox flow batteries, which are applied to two redox-active electrolytes: 2,6-dihydroxyanthraquinone (DHAQ) and 4,4′-((9,10-anthraquinone-2,6-diyl)dioxy) dibutyrate (DBEAQ). In the first method, we monitor the changes in the 1H NMR shift of the liquid electrolyte as it flows out of the electrochemical cell. In the second method, we observe the changes that occur simultaneously in the positive and negative electrodes in the full electrochemical cell. Using the bulk magnetization changes (observed via the 1H NMR shift of the water resonance) and the line broadening of the 1H shifts of the quinone resonances as a function of the state of charge, we measure the potential differences of the two single-electron couples, identify and quantify the rate of electron transfer between the reduced and oxidized species, and determine the extent of electron delocalization of the unpaired spins over the radical anions. These NMR techniques enable electrolyte decomposition and battery self-discharge to be explored in real time, and show that DHAQ is decomposed electrochemically via a reaction that can be minimized by limiting the voltage used on charging. We foresee applications of these NMR methods in understanding a wide range of redox processes in flow and other electrochemical systems.
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