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- Chien, Yu-Chuan, 1990-, et al.
(författare)
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Cellulose Separators With Integrated Carbon Nanotube Interlayers for Lithium-Sulfur Batteries : An Investigation into the Complex Interplay between Cell Components
- 2019
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 166:14, s. A3235-A3241
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Tidskriftsartikel (refereegranskat)abstract
- This work aims to address two major roadblocks in the development of lithium-sulfur (Li-S) batteries: the inefficient deposition of Li on the metallic Li electrode and the parasitic "polysulfide redox shuttle". These roadblocks are here approached, respectively, by the combination of a cellulose separator with a cathode-facing conductive porous carbon interlayer, based on their previously reported individual benefits. Both approaches result in significant improvements in cycle life in test cells with positive electrodes with practically relevant specifications. Despite the substantially prolonged cycle life, the combination of the interlayer and cellulose separator generates an increase in polysulfide shuttle current, leading to greatly reduced Coulombic efficiency. Based on XPS analyses, the latter is ascribed to a change in the composition of the solid electrolyte interphase (SEI) on the Li electrode. At the same time, the rate of electrolyte decomposition is found to be lower in cells with cellulose-based separators, which corroborates the observation of longer cycle life. These seemingly contradictory and counterintuitive observations demonstrate the complicated interactions between the cell components in the Li-S system and how strategies aiming to mitigate one unwanted process may exacerbate another. This study demonstrates the value of a holistic approach to the development of Li-S chemistry.
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| 2. |
- Chien, Yu-Chuan, 1990-, et al.
(författare)
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Electrochemical Analysis of Modified Separators for Li-S Batteries
- 2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The lithium-sulfur system is one of the potential energy storage technologies of the next generation due to the high theoretical specific capacity (1672 mAh/g), abundance and nontoxicity of sulfur [1]. However, there are still challenges yet to be overcome, one of which is the ‘polysulfide shuttle’ [1]. In order to address this issue, several modifications of the separators have been proposed. For example, longer cycle life, higher Coulombic efficiency and higher specific capacities have been reported with metal oxide coatings [2] and conductive interlayers [3,4] on the separators. Performance improvements in one or more of these properties have been ascribed to a suppression of polysulfide transport across the separator, even though this has not always been correlated with the difference in electrochemistry. In this work, the Intermittent Current Interruption (ICI) method [5] is applied to monitor the evolution of internal resistance of Li-S cells with different separators during repeated charge and discharge. Cells with different separators exhibit significant differences in resistance as a function of state-of-charge in the initial cycles, as shown in the figure. Complemented by self-discharge tests and impedance spectroscopy at selected states of charge, the roles of the interlayers in the system can be further interpreted electrochemically. This work aims to associate the electrochemical properties of the interlayers to their corresponding microstructural counterparts, which can in turn facilitate further development of the interlayer materials. Figure: Internal resistance of cells vs specific charge for Li-S cells with different separators (Zero charge indicates the fully charged state.) for the 2nd, 5th and 10th cycles at C/10 rate. References:[1] S. Urbonaite, T. Poux, P. Novák, Adv. Energy Mater. 5 (2015) 1–20.[2] Z. Zhang, Y. Lai, Z. Zhang, K. Zhang, J. Li, Electrochim. Acta 129 (2014) 55–61.[3] H. Yao, K. Yan, W. Li, G. Zheng, D. Kong, Z.W. Seh, V.K. Narasimhan, Z. Liang, Y. Cui, Energy Environ. Sci. 7 (2014) 3381–3390.[4] J. Balach, T. Jaumann, M. Klose, S. Oswald, J. Eckert, L. Giebeler, Adv. Funct. Mater. 25 (2015) 5285–5291.[5] M.J. Lacey, K. Edström, D. Brandell, Chem. Commun. 51 (2015) 16502–16505.
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| 3. |
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| 4. |
- Gunasekara, Saman Nimali, et al.
(författare)
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Polyols as phase change materials for low-grade excess heat storage
- 2014
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Ingår i: Energy Procedia. - : Elsevier. ; , s. 664-669
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Konferensbidrag (refereegranskat)abstract
- Polyols are an emerging phase change materials (PCM) category for thermal energy storage (TES), with moderate phase change temperatures and considerable enthalpies. These can be employed in systems for harvesting surplus energy from, industrial and power generation processes. However, knowledge on the properties of polyols in relation to desirable PCM properties is presently sparse and rather inconsistent. This work summarizes a literature review on polyols as PCM for TES. In addition, preliminary T-History characterization of some selected polyols was done. This study is expected to be an initiation of an extensive polyol phase equilibrium evaluation.
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| 5. |
- Gunasekara, Saman Nimali, 1982-, et al.
(författare)
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Polyols as phase change materials for surplus thermal energy storage
- 2016
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Ingår i: Applied Energy. - : Elsevier. - 0306-2619 .- 1872-9118. ; 162, s. 1439-1452
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Tidskriftsartikel (refereegranskat)abstract
- Storing low-temperature surplus thermal energy from industries, power plants, and the like, using phasechange materials (PCM) is an effective alternative in alleviating the use of fossil based thermal energyprovision. Polyols; of some also known as sugar alcohols, are an emerging PCM category for thermalenergy storage (TES). A review on polyols as PCM for TES shows that polyols have phase change temperaturesin the range of 15 to 245 C, and considerable phase change enthalpies of 100–413 kJ/kg. However,the knowledge on the thermo-physical properties of polyols as desirable PCM for TES design is presentlysparse and rather inconsistent. Moreover, the phase change and state change behaviors of polyols need tobe better-understood in order to use these as PCM; e.g. the state change glass transition which manypolyols at pure state are found to undergo. In this work preliminary material property characterizationwith the use of Temperature-History method of some selected polyols, Erythritol, Xylitol andPolyethylene glycol (PEG) 10,000 were done. Complex behaviors were observed for some of the polyols.These are: two different melting temperatures, 118.5–120 C and 106–108 C at different cycles and anaverage subcooling 18.5 C of for Erythritol, probable glass-transition between 0 and 113 C for Xylitol,as well as a thermally activated change that is likely an oxidation, after three to five heating/coolingcycles for Xylitol and Erythritol. PEG 10,000 had negligible subcooling, no glass-transition nor thermallyactivated oxidation. However a hysteresis of around 10 C was observed for PEG 10,000. Therefore thesematerials require detailed studies to further evaluate their PCM-suitability. This study is expected to be an initiation of an upcoming extensive polyol-blends phase equilibrium evaluation.
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| 6. |
- Huang, Yu-Kai, et al.
(författare)
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First-Cycle Oxidative Generation of Lithium Nucleation Sites Stabilizes Lithium-Metal Electrodes
- 2021
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Ingår i: Advanced Energy Materials. - : John Wiley & Sons. - 1614-6832 .- 1614-6840. ; 11:9
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Tidskriftsartikel (refereegranskat)abstract
- Although lithium-metal electrodes have very high capacities, their use as negative electrodes in batteries is associated with stability and safety problems due to formation of dendrites, mossy as well as dead lithium. These problems generally result from the difficulty to ensure that the deposition and stripping of lithium occur homogeneously on the entire electrode surface. As a result, the lithium-metal electrode is gradually transformed into a thick, porous, and poorly performing electrode. It is therefore essential to develop approaches that facilitate the attainment of homogeneous (i.e., 2D) lithium nucleation and growth. It is also important to note that if the lithium electrode is oxidized on the first half-cycle, the formed oxidation pits will control the subsequent lithium deposition step. Herein, it is shown that the performance of lithium-metal electrodes can be straightforwardly improved by introducing a short (e.g., 1 s long) potentiostatic pulse so that the first oxidation step takes place more homogeneously on the lithium surface. This surface activation step gives rise to a large number of preferential lithium nucleation sites facilitating the subsequent attainment of a uniform lithium deposition step. The experimental results indicate that this straightforward pulse approach can significantly increase the lifetime of lithium-metal electrodes.
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| 7. |
- Lindgren, Fredrik, et al.
(författare)
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On the Capacity Losses Seen for Optimized Nano-Si Composite Electrodes in Li-Metal Half-Cells
- 2019
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Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6832 .- 1614-6840. ; 9:33
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Tidskriftsartikel (refereegranskat)abstract
- While the use of silicon‐based electrodes can increase the capacity of Li‐ion batteries considerably, their application is associated with significant capacity losses. In this work, the influences of solid electrolyte interphase (SEI) formation, volume expansion, and lithium trapping are evaluated for two different electrochemical cycling schemes using lithium‐metal half‐cells containing silicon nanoparticle–based composite electrodes. Lithium trapping, caused by incomplete delithiation, is demonstrated to be the main reason for the capacity loss while SEI formation and dissolution affect the accumulated capacity loss due to a decreased coulombic efficiency. The capacity losses can be explained by the increasing lithium concentration in the electrode causing a decreasing lithiation potential and the lithiation cut‐off limit being reached faster. A lithium‐to‐silicon atomic ratio of 3.28 is found for a silicon electrode after 650 cycles using 1200 mAhg−1 capacity limited cycling. The results further show that the lithiation step is the capacity‐limiting step and that the capacity losses can be minimized by increasing the efficiency of the delithiation step via the inclusion of constant voltage delithiation steps. Lithium trapping due to incomplete delithiation consequently constitutes a very important capacity loss phenomenon for silicon composite electrodes.
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| 8. |
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| 9. |
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| 10. |
- Liu, Chenjuan, 1988-, et al.
(författare)
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On the Stability of NaO2 in Na–O2 Batteries
- 2018
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 10:16, s. 13534-13541
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Tidskriftsartikel (refereegranskat)abstract
- Na–O2 batteries are regarded as promising candidates for energy storage. They have higher energy efficiency, rate capability, and chemical reversibility than Li–O2 batteries; in addition, sodium is cheaper and more abundant compared to lithium. However, inconsistent observations and instability of discharge products have inhibited the understanding of the working mechanism of this technology. In this work, we have investigated a number of factors that influence the stability of the discharge products. By means of in operando powder X-ray diffraction study, the influence of oxygen, sodium anode, salt, solvent, and carbon cathode were investigated. The Na metal anode and an ether-based solvent are the main factors that lead to the instability and decomposition of NaO2 in the cell environment. This fundamental insight brings new information on the working mechanism of Na–O2 batteries.
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