| 151. |
- Shi, Ziyi, et al.
(författare)
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Bio-based anode material production for lithium–ion batteries through catalytic graphitization of biochar : the deployment of hybrid catalysts
- 2024
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Producing sustainable anode materials for lithium-ion batteries (LIBs) through catalytic graphitization of renewable biomass has gained significant attention. However, the technology is in its early stages due to the bio-graphite's comparatively low electrochemical performance in LIBs. This study aims to develop a process for producing LIB anode materials using a hybrid catalyst to enhance battery performance, along with readily available market biochar as the raw material. Results indicate that a trimetallic hybrid catalyst (Ni, Fe, and Mn in a 1:1:1 ratio) is superior to single or bimetallic catalysts in converting biochar to bio-graphite. The bio-graphite produced under this catalyst exhibits an 89.28% degree of graphitization and a 73.95% conversion rate. High-resolution transmission electron microscopy (HRTEM) reveals the dissolution–precipitation mechanism involved in catalytic graphitization. Electrochemical performance evaluation showed that the trimetallic hybrid catalyst yielded bio-graphite with better electrochemical performances than those obtained through single or bimetallic hybrid catalysts, including a good reversible capacity of about 293 mAh g−1 at a current density of 20 mA/g and a stable cycle performance with a capacity retention of over 98% after 100 cycles. This study proves the synergistic efficacy of different metals in catalytic graphitization, impacting both graphite crystalline structure and electrochemical performance.
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| 152. |
- Sobkowiak, Adam, et al.
(författare)
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Understanding and Controlling the Surface Chemistry of LiFeSO4F for an Enhanced Cathode Functionality
- 2013
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 25:15, s. 3020-3029
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Tidskriftsartikel (refereegranskat)abstract
- The tavorite polymorph of LiFeSO4F has recently attracted a lot of interest as a cathode material for lithium ion batteries stimulated by its competitive specific capacity, high potential for the Fe2+/Fe3+ redox couple, and low-temperature synthesis. However, the synthesis routes explored to date have resulted in notably varied electrochemical performance. This inconsistency is difficult to understand given the excellent purity, crystallinity, and similar morphologies achieved via all known methods. In this work, we examine the role of the interfacial chemistry on the electrochemical functionality of LiFeSO4F. We demonstrate that particularly poor electrochemical performance may be obtained for pristine materials synthesized in tetraethylene glycol (TEG), which represents one of the most economically viable production methods. By careful surface characterization, we show that this restricted performance can be largely attributed to residual traces of TEG remaining on the surface of pristine materials, inhibiting the electrochemical reactions. Moreover, we show that optimized cycling performance of LiFeSO4F can be achieved by removing the unwanted residues and applying a conducting polymer coating, which increases the electronic contact area between the electrode components and creates a highly percolating network for efficient electron transport throughout the composite material. This coating is produced using a simple and scalable method designed to intrinsically favor the functionality of the final product.
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| 153. |
- Storm, Mie Møller, et al.
(författare)
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Capillary based Li-air batteries for in situ synchrotron X-ray powder diffraction studies
- 2015
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Ingår i: Journal of Materials Chemistry A. - 2050-7488. ; 3, s. 3113-3119
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Tidskriftsartikel (refereegranskat)abstract
- For Li-air batteries to reach their full potential as energy storage system, a complete understanding of the conditions and reactions in the battery during operation is needed. To follow the reactions in situ a capillary-based Li-O2 battery has been developed for synchrotron-based in situ X-ray powder diffraction (XRPD). In this article, we present the results for the analysis of 1st and 2nd deep discharge and charge for a cathode being cycled between 2 and 4.6 V. The crystalline precipitation of Li2O2 only is observed in the capillary battery. However, there are indications of side reactions. The Li2O2 diffraction peaks grow with the same rate during charge and the development of the full width at half maximum (FWHM) is hkl dependent. The difference in the FWHM of the 100 and the 102 reflections indicate anisotropic morphology of the Li2O2 crystallites or defects along the c-axis. The effect of constant exposure of X-ray radiation to the electrolyte and cathode during charge of the battery was also investigated. X-ray exposure during charge leads to changes in the development of the intensity and the FWHM of the Li2O2 diffraction peaks. The X-ray diffraction results are supported by ex situ X-ray photoelectron spectroscopy (XPS) of discharged cathodes to illuminate non-crystalline deposited materials.
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| 154. |
- Storm, Mie Møller, et al.
(författare)
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In Situ Analysis of the Li-O-2 Battery with Thermally Reduced Graphene Oxide Cathode : Influence of Water Addition
- 2016
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 120:38, s. 21211-21217
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Tidskriftsartikel (refereegranskat)abstract
- The Li-O-2 battery technology holds the promise to deliver a battery with significantly increased specific energy compared to today's Li-ion batteries. As a cathode support material, reduced graphene oxide has received increasing attention in the Li-O-2 battery community due to the possibility of increased discharge capacity, increased battery cyclability, and decreased, charging, overpotential. In this. article we investigate the effect of water on a thermally, redircedigraphene, oxide cathode in a Li-O-2 battery. Differential electrochemical mass spectrciscnieveals a, decreased electron count for batteries with 1000 ppm water added- to the electrolyte in comparison to dry batteries, indicating additional parasitic electrochemical or chemical processes. A comparable capacity of the wet and dry batteries indicates that the reaction mechanism in the Li-O-2 battery also depends on the 'surface-of-the cathode and not only on addition of water to the electrolyte as demonstrated by the solution-based mechanism In situ synchrotron X-ray diffraction experiment using a new design of a capillary-based Li-O-2 cell with a thermally reduced graphene oxide cathode shows formation of LiOH along with Li2O2.
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| 155. |
- Storm, Mie Møller, et al.
(författare)
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Reduced graphene oxide for Li-€“air batteries : The effect of oxidation time and reduction conditions for graphene oxide
- 2015
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Ingår i: Carbon. - : Elsevier BV. - 0008-6223 .- 1873-3891. ; 85, s. 233-244
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Tidskriftsartikel (refereegranskat)abstract
- Reduced graphene oxide (rGO) has shown great promise as an air-cathode for Li–air batteries with high capacity. In this article we demonstrate how the oxidation time of graphene oxide (GO) affects the ratio of different functional groups and how trends of these in GO are extended to chemically and thermally reduced GO. We investigate how differences in functional groups and synthesis may affect the performance of Li–O2 batteries. The oxidation timescale of the GO was varied between 30min and 3days before reduction. Powder X-ray diffraction, micro-Raman, FE-SEM, BET analysis, and XPS were used to characterize the GO’s and rGO’s. Selected samples of GO and rGO were analyzed by solid state 13C MAS NMR. These methods highlighted the difference between the two types of rGO’s, and XPS indicated how the chemical trends in GO are extended to rGO. A comparison between XPS and 13C MAS NMR showed that both techniques can enhance the structural understanding of rGO. Different rGO cathodes were tested in Li–O2 batteries which revealed a difference in overpotentials and discharge capacities for the different rGO’s. We report the highest Li–O2 battery discharge capacity recorded of approximately 60,000mAh/gcarbon achieved with a thermally reduced GO cathode.
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| 156. |
- Sveinbjörnsson, Dadi, et al.
(författare)
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Ionic conductivity and the formation of cubic CaH2 in the LiBH4–Ca(BH4)2 composite
- 2014
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Ingår i: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596 .- 1095-726X. ; 211:0, s. 81-89
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Tidskriftsartikel (refereegranskat)abstract
- Abstract LiBH4–Ca(BH4)2 composites were prepared by ball milling. Their crystal structures and phase composition were investigated using synchrotron X-ray diffraction and Rietveld refinement, and their ionic conductivity was measured using impedance spectroscopy. The materials were found to form a physical mixture. The composites were composed of α-Ca(BH4)2, γ-Ca(BH4)2 and orthorhombic LiBH4, and the relative phase quantities of the Ca(BH4)2 polymorphs varied significantly with LiBH4 content. The formation of small amounts of orthorhombic CaH2 and cubic CaH2 in a CaF2-like structure was observed upon heat treatment. Concurrent formation of elemental boron may also occur. The ionic conductivity of the composites was measured using impedance spectroscopy, and was found to be lower than that of ball milled LiBH4. Electronic band structure calculations indicate that cubic CaH2 with hydrogen defects is electronically conducting. Its formation along with the possible precipitation of boron therefore has an effect on the measured conductivity of the LiBH4–Ca(BH4)2 composites and may increase the risk of an internal short-circuit in the cells.
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| 157. |
- Szczesna-Chrzan, Anna, et al.
(författare)
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Systematic Studies on Liquid Sodium 4,5-dicyano-2-(trifluoromethyl)imidazolate (NaTDI)-Based Electrolytes and Its Impact on the Cycling Behaviour Against Wet Impregnated WI-NaNMC and Prussian White Cathodes
- 2022
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Ingår i: Advanced Materials Interfaces. - : John Wiley & Sons. - 2196-7350. ; 9:8
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Tidskriftsartikel (refereegranskat)abstract
- The article describes a research on new salts and cathode materials dedicated to sodium cells. Sodium technology is considered to be one of the most promising (for new battery generations) and has been very actively (re)-developed for more than a decade. The first part of this work is mainly focused on electrochemical studies of the low coordinating Huckel type salt (4,5-dicyano-2-(trifluoromethyl)imidazolate, NaTDI)-based electrolytes with and without solid electrolyte interface modified additives: fluoroethylene carbonate (FEC). In the second part electrolytes are tested in a half-cells with layered oxides. Sodium nickel-manganese-cobalt oxide (NaNMC) and WI-NaNMC-333 and WI-NaNMC-622 layered cathode materials are prepared by wet impregnation synthesis (WI) routine. Prussian White is obtained from University of Uppsala group to compare and initial electrochemical properties against electrolyte with NaTDI. Basic physicochemical properties of the obtained powders are also reported in the manuscript. The best properties are recorded for 0.75 m NaTDI in EC:DMC (1:1 v/v) with 3% FEC additive by its conductivity (11.52 mS cm(-1) for 20 degrees C). The same solution also shows promising results during electrochemical tests in half-cell geometry against WI-NaNMC-622 cathode (114.22 mAh g(-1) after 1 cycle C/20). NaPF6 salt is used as an electrolyte as a commercially available reference.
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| 158. |
- Sångeland, Christofer, et al.
(författare)
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Dissecting the solid polymer electrolyte–electrode interface in the vicinity of electrochemical stability limits
- 2022
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 14:25, s. 28716-28728
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Tidskriftsartikel (refereegranskat)abstract
- Proper understanding of solid polymer electrolyte–electrode interfacial layer formation and its implications on cell performance is a vital step toward realizing practical solid-state lithium-ion batteries. At the same time, probing these solid–solid interfaces is extremely challenging as they are buried within the electrochemical system, thereby efficiently evading exposure to surface-sensitive spectroscopic methods. Still, the probing of interfacial degradation layers is essential to render an accurate picture of the behavior of these materials in the vicinity of their electrochemical stability limits and to complement the incomplete picture gained from electrochemical assessments. In this work, we address this issue in conjunction with presenting a thorough evaluation of the electrochemical stability window of the solid polymer electrolyte poly(ε-caprolactone):lithium bis(trifluoromethanesulfonyl)imide (PCL:LiTFSI). According to staircase voltammetry, the electrochemical stability window of the polyester-based electrolyte was found to span from 1.5 to 4 V vs Li+/Li. Subsequent decomposition of PCL:LiTFSI outside of the stability window led to a buildup of carbonaceous, lithium oxide and salt-derived species at the electrode–electrolyte interface, identified using postmortem spectroscopic analysis. These species formed highly resistive interphase layers, acting as major bottlenecks in the SPE system. Resistance and thickness values of these layers at different potentials were then estimated based on the impedance response between a lithium iron phosphate reference electrode and carbon-coated working electrodes. Importantly, it is only through the combination of electrochemistry and photoelectron spectroscopy that the full extent of the electrochemical performance at the limits of electrochemical stability can be reliably and accurately determined.
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| 159. |
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| 160. |
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