| 1. |
- Lodge, Andrew W., et al.
(författare)
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Critical appraisal on the role of catalysts for the oxygen reduction reaction in lithium-oxygen batteries
- 2014
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 140, s. 168-173
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Tidskriftsartikel (refereegranskat)abstract
- This work reports a detailed characterization of the reduction of oxygen in pyrrolidinium-based ionic liquids for application to lithium-oxygen batteries. It is found that, in the absence of Li+, all electron transfer kinetics are fast, and therefore, the reactions are limited by the mass transport rate. Reversible reduction of O-2 to O-2(center dot-) and O-2(center dot-) to O-2(2-) take place at E-0 = 2.1 V and 0.8 V vs. Li+/Li, respectively. In the presence of Li+, O-2 is reduced to LiO2 first and then to Li2O2. The solubility product constant of Li2O2 is found to be around 10(-51), corroborating the hypothesis that electrode passivation by Li2O2 deposition is an important issue that limits the capacity delivered by lithium-oxygen batteries. Enhancing the rate of Li2O2 formation by using different electrode materials would probably lead to faster electrode passivation and hence smaller charge due to oxygen reduction (smaller capacity of the battery). On the contrary, soluble redox catalysts can not only increase the reaction rate of Li2O2 formation but also avoid electrode passivation since the fast diffusion of the soluble redox catalyst would displace the formation of Li2O2 at a sufficient distance from the electrode surface.
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| 2. |
- Lacey, Matthew J, et al.
(författare)
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Analysis of soluble intermediates in the lithium-sulfur battery by a simple in situ electrochemical probe
- 2014
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Ingår i: Electrochemistry communications. - : Elsevier BV. - 1388-2481 .- 1873-1902. ; 46, s. 91-93
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a simple setup using a thin, insulated platinum wire as an in situ electrochemical probe for analysis of the soluble polysulfide intermediates formed and consumed during the course of the discharge process of a lithium-sulfur cell. The probe, sharing common reference and counter electrodes with the cell, can be used to follow the changes in concentration of polysulfides in the electrolyte. The results herein both support and complement more advanced techniques studied elsewhere for understanding the dominant processes occurring in the cell.
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| 3. |
- Lacey, Matthew J., et al.
(författare)
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Functional, water-soluble binders for improved capacity and stability of lithium-sulfur batteries
- 2014
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 264, s. 8-14
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Tidskriftsartikel (refereegranskat)abstract
- Binders based on mixtures of poly(ethylene oxide) (PEO) and poly(vinylpyrrolidone) (PVP) are here shown to significantly improve the reversible capacity and capacity retention of lithium- sulfur batteries compared to conventional binders. This mixed binder formulation combines the local improvement to the solvent system offered by PEO and the lithium (poly)sulfide-stabilising effect of PVP. Cells with cathodes made of simple mixtures of sulfur powder and carbon black with a binder of 4:1 PEO:PVP exhibited a reversible capacity of over 1000 mAh g(-1) at C/5 after 50 cycles and 800 mAh g(-1) at 1C after 200 cycles. Furthermore, these materials are water soluble, environmentally friendly and widely available, making them particularly interesting for large-scale production and applications in, for example, electric vehicles.
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| 4. |
- Lacey, Matthew J., et al.
(författare)
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Porosity Blocking in Highly Porous Carbon Black by PVdF Binder and Its Implications for the Li-S System
- 2014
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 118:45, s. 25890-25898
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Tidskriftsartikel (refereegranskat)abstract
- In this work, the influence of cathode binders on the porosity of composite electrodes for lithiumsulfur (LiS) batteries employing high surface area carbon blacks has been closely scrutinized. This has been accomplished by comparison of PVdF with the related copolymer, PVdF-HFP. Analysis of carbon black porosity after addition of binder in NMP solution reveals that PVdF(-HFP) fills pores of almost any size in carbon black, which can effect a severe reduction in pore volume and surface area accessible to the electrolyte in a LiS cell. Noting the different swelling behavior of both binders, the implications of pore filling by the binder on the electrochemistry of LiS cells can be determined. Because of the low swellability of PVdF in dimethoxyethane:dioxolane (DME:DOL)-based electrolytes, access of the electrolyte to the carbon surface area and pore volume is restricted, with potentially severe detrimental effects on the available capacity of the cell. Furthermore, this effect is still clearly significant for common binder loadings and with preinfiltration of sulfur; this study is therefore a clear demonstration that PVdF is an unsuitable choice of binder for the lithiumsulfur system and that alternatives must be considered.
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| 5. |
- Lacey, Matthew J., et al.
(författare)
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Why PEO as a binder or polymer coating increases capacity in the Li-S system
- 2013
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 49:76, s. 8531-8533
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Tidskriftsartikel (refereegranskat)abstract
- PEO, used either as a binder or a polymer coating, and PEGDME, used as an electrolyte additive, are shown to increase the reversible capacity of Li-S cells. The effect, in all three cases, is the same: an improved solvent system for the electrochemistry of sulfur species and suppression of cathode passivation on discharge. This constitutes a novel interpretation of the mechanistic behaviour of polyethers in the Li-S system, and sheds new light upon several previous studies.
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| 6. |
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