| 2. |
- Chien, Yu-Chuan, et al.
(författare)
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Development of operando XRD coin cells for lithium-sulfur batteries
- 2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Lithium-sulfur (Li-S) batteries has been regarded as one of the promising technology for the next generation of rechargeable batteries due to its high theoretical energy density (2600 Wh/kg [1]). Several works [2–7] on operando X-ray diffraction (XRD) of the Li-S system have been published; however, their experimental setups showed one or more of the following drawbacks. First, the amount of electrolyte was often not reported or would be considered too high for a common Li-S cell, which has been demonstrated to have a significant impact on the behavior of the system [8]. Another issue is the non-uniform stack pressure and electron conductivity of the operando cell setup, whose effects were found by both experiments and simulations [9].This work aims to tackle with the above-mentioned issues by modifying commercial coin cells and using X-ray transparent metal, beryllium, as the spacers. By doing so, the electron conductivity and stack pressure can be expected to be uniform throughout the electrodes. The amount of electrolyte can also be precisely controlled since no vacuum-sealing is required for coin cells. A preliminary diffraction pattern obtained with the cell setup can be seen in Fig. 1. With electrochemical properties similar to common Li-S cells, ‘online’ electrochemical characterization techniques, e.g. Intermittent Current Interruption (ICI) method for following cell resistance [10], will be applicable with operando XRD, revealing more information about this complex system.Figure 1 XRD patterns of alpha-S and electrode material in the modified coin cell.References[1] J. Tan, et al., Nanoscale (2017) 19001–19016.[2] J. Nelson, et al., J. Am. Chem. Soc. 134 (2012) 6337–6343.[3] N.A. Cañas, et al., J. Power Sources 226 (2013) 313–319.[4] S. Waluś, et al., Chem. Commun. 49 (2013) 7899.[5] M. a. Lowe, et al., RSC Adv. 4 (2014) 18347.[6] J. Kulisch, et al., Phys. Chem. Chem. Phys. 16 (2014) 18765–18771.[7] J. Conder, et al., Nat. Energy 2 (2017) 1–7.[8] M.J. Lacey, ChemElectroChem (2017) 1–9.[9] O.J. Borkiewicz, et al., J. Phys. Chem. Lett. 6 (2015) 2081–2085.[10] M.J. Lacey, et al., Chem. Commun. 51 (2015) 16502–16505.
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| 3. |
- Naylor, Andrew J., et al.
(författare)
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Depth-dependent oxygen redox activity in lithium-rich layered oxide cathodes
- 2019
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488. ; 7:44, s. 25355-25368
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Tidskriftsartikel (refereegranskat)abstract
- Lithium-rich materials, such as Li1.2Ni0.2Mn0.6O2, exhibit capacities not limited by transition metal redox, through the reversible oxidation of oxide anions. Here we offer detailed insight into the degree of oxygen redox as a function of depth within the material as it is charged and cycled. Energy-tuned photoelectron spectroscopy is used as a powerful, yet highly sensitive technique to probe electronic states of oxygen and transition metals from the top few nanometers at the near-surface through to the bulk of the particles. Two discrete oxygen species are identified, On− and O2−, where n < 2, confirming our previous model that oxidation generates localised hole states on O upon charging. This is in contrast to the oxygen redox inactive high voltage spinel LiNi0.5Mn1.5O4, for which no On− species is detected. The depth profile results demonstrate a concentration gradient exists for On− from the surface through to the bulk, indicating a preferential surface oxidation of the layered oxide particles. This is highly consistent with the already well-established core–shell model for such materials. Ab initio calculations reaffirm the electronic structure differences observed experimentally between the surface and bulk, while modelling of delithiated structures shows good agreement between experimental and calculated binding energies for On−.
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