| 1. |
- Amin, Muhammad, 1979, et al.
(författare)
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Coin-cell Supercapacitors Based on CVD Grown and Vertically Aligned Carbon Nanofibers (VACNFs)
- 2017
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Ingår i: International Journal of Electrochemical Science. - : Elsevier BV. - 1452-3981. ; 12:7, s. 6653-6661
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Tidskriftsartikel (refereegranskat)abstract
- Complete supercapacitors (SCs) comprising vertically aligned carbon nanofibers (VACNFs) as electrode materials have been assembled as coin-cells. The VACNFs were grown directly onto the current collector by direct current plasma enhanced chemical vapor deposition (DC-PECVD), thereby providing excellent contact with the current collector, but also eliminating the need of any binder. The vertical alignment facilitates fast ion transport and the electrolyte to access the entire surface of the CNFs. The morphology of the VACNFs was evaluated by scanning electron microscopy (SEM), while the performance was assessed by several methods: cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and device related cycling by galvanostatic charge/discharge. The capacitance, 3.64 mF/cm2 , is >15 times higher than the capacitance of a coin-cell without CNFs and the cyclic performance shows these proof-of-concept SCs to retain >80% of the capacitance after 2000 full charge/discharge cycles. The direct growth of VACNFs as electrodes at the current collector opens pathways for SC production using existing coin-cell battery production technology.
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| 2. |
- Boschin, Andrea, 1981, et al.
(författare)
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Characterization of NaX (X: TFSI, FSI) - PEO based solid polymer electrolytes for sodium batteries
- 2015
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686. ; 175, s. 124-133
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Tidskriftsartikel (refereegranskat)abstract
- Solid polymers electrolytes (SPEs) based on sodium bis(fluorosulfonyl) imide (NaFSI) and poly(ethylene oxide) (PEO) with different ether oxygen to sodium (O:Na) molar ratios (n), resulting in NaFSI(PEO) n materials are here presented for the first time. These SPEs are extensively compared with the corresponding NaTFSI(PEO)(n) system in terms of ionic conductivities, thermal properties, and charge carriers - to in detail outline both the role of the different anions used and the salt concentrations employed. While for the most dilute systems (n = 20) the two SPE families show similar ionic conductivities in the entire temperature range investigated (273-343 K), for n = 6 and n = 9 they differ significantly; at room temperature, the NaFSI based SPEs show lower ionic conductivities than the NaTFSI based analogues. This difference is mainly ascribed to differences in the morphology; while the NaTFSI salt, possibly by virtue of its large TFSI anion, acts to inhibit crystallization, NaFSI rather seems to favor crystallization. Furthermore, careful Raman spectroscopy analysis of the charge carrier speciation reveal higher aggregates to be present in the most concentrated SPE, NaFSI(PEO)(6), and the NaFSI based SPEs in general to result in less "free" anions than the NaTFSI based SPEs. Moreover, as both NaTFSI(PEO)(n) and NaFSI(PEO)(n) for n = 20 and n = 9 exhibit very similar glass transition temperatures, the FSI ion seem to be equally plasticizing as the TFSI ion, but for n = 6 the different speciation in terms of charge carriers also affects the relative dynamics of the polymer chains.
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| 3. |
- Boschin, Andrea, 1981, et al.
(författare)
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On the Feasibility of Sodium Metal as Pseudo-Reference Electrode in Solid State Electrochemical Cells
- 2017
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Ingår i: ChemElectroChem. - : Wiley. - 2196-0216. ; 4:10, s. 2717-2721
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Tidskriftsartikel (refereegranskat)abstract
- A set-up of a sodium metal anode vs. a solid polymer electrolyte (SPE) comprising poly(ethylene oxide) (PEO) and sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) has been evaluated in detail for the feasibility to use sodium metal as a pseudo-reference electrode (pseudo-RE). To evaluate the stability and reproducibility, we monitored the half-wave potential (E-1/2) of added decamethylferrocene (Me(10)Fc) and the stability of the interface by electrochemical impedance spectroscopy (EIS). The sodium/SPE interface resistance (R-Na/SPE) increases with time, up to 2.8k Omega cm(-2), and causes the E-1/2 of the Me(10)Fc(+/0) reference redox couple to drift up to 15mV during 88hours. Moreover, the sodium potential is very irreproducible, even initially after cell assembling the values can differ by 60mV, likely due to extreme sensitivity of the metal surface even to an "inert and dry" glove box environment. Indeed, freshly cut sodium readily reacts with water, forming NaOH, and adsorbs impurities that can be present even in a glove box atmosphere. The oxidation layer and the amount of adsorbed impurities increase with the exposure to the glove box atmosphere, as revealed by ATR-FTIR spectroscopy. Altogether, this calls for attention when evaluating any battery materials in half-cell configurations using sodium metal as the pseudo-RE.
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| 4. |
- Boschin, Andrea, 1981, et al.
(författare)
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Plasticization of NaX-PEO solid polymer electrolytes by Pyr(13)X ionic liquids
- 2016
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686. ; 211, s. 1006-1015
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Tidskriftsartikel (refereegranskat)abstract
- Addition of moderate contents (≤20 wt%) of ionic liquids (ILs) to binary solid polymer electrolytes (SPEs) is made to alter the overall SPE properties, foremost to increase the room temperature ionic conductivity. Sodium conducting ternary electrolytes, based on sodium salts; NaTFSI and NaFSI, the polymer poly(ethylene oxide) (PEO), and pyrrolidinium ILs; Pyr13TFSI and Pyr13FSI, with different compositions: NaX(PEO)n – Pyr13X (X = TFSI, FSI), have been prepared. Raman and dielectric spectroscopy as well as differential scanning calorimetry have been used to evaluate the plasticizing effect of the Pyr13 IL cation and the accompanying TFSI and FSI IL anions via changes in ionic association, crystallinity, polymer chain dynamics, and total ionic conductivity. While all the TFSI based systems seem rather insensitive to the addition of IL with respect to speciation, the situation is much less clear for the FSI based systems. Furthermore, the addition of ILs seems beneficial for inhibiting PEO crystallization, especially for the FSI anion, and also for enhancing the polymer chain dynamics, but yet the FSI based ternary electrolytes show lower ion conductivities as compared to the analogous TFSI based systems.
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| 5. |
- 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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| 6. |
- 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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| 7. |
- 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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