| 1. |
- Cavallo, Carmen, 1986, et al.
(författare)
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A free-standing reduced graphene oxide aerogel as supporting electrode in a fluorine-free Li2S8 catholyte Li-S battery
- 2019
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 416, s. 111-117
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Tidskriftsartikel (refereegranskat)abstract
- We report on a novel, simple, and environmentally benign synthesis route for a free-standing reduced graphene oxide (r-GO) aerogel and its application as supporting electrode for the electrochemical redox reaction of sulphur in a catholyte-based lithium-sulphur battery. A mesoporous matrix is formed by a layers of r-GO, providing sites for electrochemical reactions and a highly conducting pathway for electrons. The highly porous structure is easily infiltrated by a catholyte solution providing a homogeneous distribution of the sulphur active material in the conductive graphene matrix and ensuring efficient electrochemical reactions. This is demonstrated by a high capacity, 3.4 mAh cm−2, at high mass loading, 3.2 mg cm−2 of sulphur in the cathode and in total the sulphur loading in the Li-S cell is even double (6.4 mg cm−2). Additionally, the presence of oxygen groups in the r-GO aerogel structure stabilizes the cycling performance and the Li-S cell with the fluorine free catholyte shows a capacity retention of 85% after 350 cycles.
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| 2. |
- Lindberg, Simon, 1987, et al.
(författare)
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Charge storage mechanism of α-MnO2 in protic and aprotic ionic liquid electrolytes
- 2020
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 460
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Tidskriftsartikel (refereegranskat)abstract
- In this work we have investigated the charge storage mechanism of MnO2 electrodes in ionic liquid electrolytes. We show that by using an ionic liquid with a cation that has the ability to form hydrogen bonds with the active material (MnO2) on the surface of the electrode, a clear faradaic contribution is obtained. This situation is found for ionic liquids with cations that have a low pKa, i.e. protic ionic liquids. For a protic ionic liquid, the specific capacity at low scan rate rates can be explained by a densely packed layer of cations that are in a standing geometry, with a proton directly interacting through a hydrogen bond with the surface of the active material in the electrode. In contrast, for aprotic ionic liquids there is no interaction and only a double layer contribution to the charge storage is observed. However, by adding an alkali salt to the aprotic ionic liquid, a faradaic contribution is obtained from the insertion of Li+ into the surface of the MnO2 electrode. No effect can be observed when Li+ is added to the protic IL, suggesting that a densely packed cation layer in this case prevent Li-ions from reaching the active material surface.
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| 3. |
- Abdelhamid, Muhammad, 1987, et al.
(författare)
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Electropolymerisation of N-Ethylanilinium Trifluoroacetate Ionic Liquid into Poly(N-Ethylaniline) and Control of its Morphology
- 2017
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Ingår i: Australian Journal of Chemistry. - 1445-0038 .- 0004-9425. ; 70:9, s. 985-989
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the electropolymerisation of pre-synthesised N-ethylanilinium trifluoroacetate, a protic ionic liquid (PIL), was carried out. The PIL served as the monomer precursor, solvent, and supporting electrolyte for the polymerisation process, and no additional acid was required due to the protic nature of the PIL. Two different morphologies of the poly(N-ethylaniline) were achieved by using different electropolymerisation approaches and the resultant films were soluble in the PIL precursor as well as a wide range of organic solvents. The use of anilinium based PILs, as polymerisation precursors, promises a greener approach for the production of polyanilines, as well as highly processable polymers.
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| 4. |
- Bitenc, Jan, et al.
(författare)
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Concept and electrochemical mechanism of an Al metal anode - organic cathode battery
- 2020
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Ingår i: Energy Storage Materials. - : Elsevier BV. - 2405-8297 .- 2405-8289. ; 24, s. 379-383
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Tidskriftsartikel (refereegranskat)abstract
- Aluminum (Al) batteries are fundamentally a promising future post-Li battery technology. The recently demonstrated concept of an Al-graphite battery represents some significant progress for the technology, but the cell energy density is still very modest and limited by the quantity of the AlCl3 based electrolyte, as it relies on AlCl4- intercalation. For further progress, cathode materials capable of an electrochemical reaction with Al positively charged species are needed. Here such a concept of an Al metal anode - organic cathode battery based on anthraquinone (AQ) electrochemistry with a discharge voltage of 1.1 V is demonstrated. Further improvement of both the cell capacity retention and rate capability is achieved by nano-structured and polymerized cathodes. The intricate electrochemical mechanism is proven to be that the anthraquinone groups undergo reduction of their carbonyl bonds during discharge and become coordinated by AlCl2+ species. Altogether the Al metal anode - AQ cathode cell has almost the double energy density of the state-of-the-art Al-graphite battery.
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| 5. |
- 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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| 6. |
- Forero Saboya, Juan, 1992, et al.
(författare)
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Solvent-free lithium and sodium containing electrolytes based on pseudo-delocalized anions
- 2019
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Ingår i: Chemical Communications. - 1364-548X .- 1359-7345. ; 55:5, s. 632-635
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Tidskriftsartikel (refereegranskat)abstract
- Mixing the standard battery salt LiTFSI with various Li-salts of novel pseudo-delocalized organic anions [N(CH3)2((CH2)nSO3)((CH2)mSO3)]− (MMnm11), results in super-cooled solvent-free liquid electrolytes with glass transition temperatures of ca. 50 °C. Synthesis routes and full chemical characterisation of the new pseudo-delocalized anions are presented, as well as phase and thermal stabilities. The ion conductivities and electrochemical stabilities are evaluated towards lithium and sodium battery application.
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| 7. |
- Forero Saboya, Juan, 1992, et al.
(författare)
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Water-in-Bisalt Electrolyte with Record Salt Concentration and Widened Electrochemical Stability Window
- 2019
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Ingår i: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 10:17, s. 4942-4946
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Tidskriftsartikel (refereegranskat)abstract
- Water-in-salt and water-in-bisalt electrolytes have recently attracted much attention due to their expanded electrochemical stability windows. The concentration limit of such electrolytes is constrained by the solubility of the lithium salts employed, ca. 21 m (mol kg−1) for LiTFSI (lithium bis(trifluoromethanesulfonyl)imide). By adding a second lithium salt, the total salt concentration can be increased, but the hydrogen evolution keeps limiting the application of such systems in batteries with low potential anodes. Herein we report a water-in-bisalt electrolyte with a record salt concentration (31.4 m LiTFSI + 7.9 m Li[N(CH3)2((CH2)3SO3)((CH2)4SO3)]) in which the bulky anion completely prevents the crystallization, even at such low water contents. Although the hydrogen evolution reaction is not completely suppressed, the expanded electrochemical stability window allows for low potential reactions such as aluminum−lithium alloying. The high salt concentration favors the formation of a suitable passivation layer that can be further engineered by modifying the anion structure
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| 8. |
- Lu, J., et al.
(författare)
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Structural, Spectroscopic, and Electrochemical Characterization of Semi-Conducting, Solvated [Pt(NH 3 ) 4 ](TCNQ) 2 ·(DMF) 2 and Non-Solvated [Pt(NH 3 ) 4 ](TCNQ) 2
- 2017
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Ingår i: Australian Journal of Chemistry. - 1445-0038 .- 0004-9425. ; 70:9, s. 997-1005
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Tidskriftsartikel (refereegranskat)abstract
- The demand for catalysts that are highly active and stable for electron-transfer reactions has been boosted by the discovery that [Pt(NH3)4](TCNQF4)2 (TCNQF4≤2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) is an efficient catalyst. In this work, we prepare and characterize the two related [Pt(NH3)4] 2+ complexes, [Pt(NH3)4](TCNQ)2·(DMF)2 (1) and [Pt(NH3)4] (TCNQ)2 (2). Reaction of [Pt(NH3)4](NO3)2 with LiTCNQ in a mixed solvent (methanol/dimethylformamide, 4:1v/v) gives [Pt(NH3)4] (TCNQ)2·(DMF)2 (1), whereas the same reaction in water affords [Pt(NH3)4](TCNQ)2 (2). 2 has been previously reported. Both 1 and 2 have now been characterized by single-crystal X-ray crystallography, Fourier-transform (FT)IR, Raman and UV-vis spectroscopy, and electrochemistry. Structurally, in 1, the TCNQ1-anions form infinite stacks with a separation between adjacent anions within the stack alternating between 3.12 and 3.42Å. The solvated structure 1 differs from the non-solvated form 2 in that pairs of TCNQ1-anions are clearly displaced from each other. The conductivities of pressed pellets of 1 and 2 are both in the semi-conducting range at room temperature. 2 can be electrochemically synthesized by reduction of a TCNQ-modified electrode in contact with an aqueous solution of [Pt(NH3)4] (NO3)2 via a nucleation growth mechanism. Interestingly, we discovered that 1 and 2 are not catalysts for the ferricyanide and thiosulfate reaction. Li+ and tetraalkylammonium salts of TCNQ1-/2-and TCNQF41-/2-were tested for potential catalytic activity towards ferricyanide and thiosulfate. Only TCNQF41-/2-salts were active, suggesting that the dianion redox level needs to be accessible for efficient catalytic activity and explaining why 1 and 2 are not good catalysts. Importantly, the origin of the catalytic activity of the highly active [Pt(NH3)4](TCNQF4)2 catalyst is now understood, enabling other families of catalysts to be developed for important electron-transfer reactions.
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| 9. |
- Paronen, M, et al.
(författare)
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The Role of Solvated Electrons in Direct Methanol Fuel Cells
- 2023
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Ingår i: ChemElectroChem. - 2196-0216. ; 10:22
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Tidskriftsartikel (refereegranskat)abstract
- Direct methanol fuel cells, DMFCs, have for long been considered as a superior alternative to rechargeable batteries for various portable applications with respect to significantly higher theoretical power densities and faster recharging by simply filling up with new liquid fuel. In reality, however, DMFCs so far have much low power densities, suffer from high fuel losses, and require extremely expensive catalysts at high loadings. Here we show that an until now not considered process at the DMFC electrodes may cause these severe losses in performance. The process is that electrons generated at nano-structured catalyst loaded electrodes become solvated into the surrounding electrolyte. Taking this new process and resulting reaction mechanism(s) fully into account, material and catalyst/electrode design should be reconsidered to realize the true potential of DMFCs.
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