| 31. |
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| 32. |
- House, Robert A., et al.
(författare)
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What Triggers Oxygen Loss in Oxygen Redox Cathode Materials?
- 2019
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Ingår i: Chemistry of Materials. - : AMER CHEMICAL SOC. - 0897-4756 .- 1520-5002. ; 31:9, s. 3293-3300
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Tidskriftsartikel (refereegranskat)abstract
- It is possible to increase the charge capacity of transition metal (TM) oxide cathodes in alkali-ion batteries by invoking redox reactions on the oxygen. However, oxygen loss often occurs. To explore what affects oxygen loss in oxygen redox materials, we have compared two analogous Na-ion cathodes, P2-Na0.67Mg0.28Mn0.72O2 and P2-Na0.78Li0.25Mn0.75O2. On charging to 4.5 V, >0.4e(-) are removed from the oxide ions of these materials, but neither compound exhibits oxygen loss. Li is retained in P2-Na0.78Li0.25Mn0.25O2 but displaced from the TM to the alkali metal layers, showing that vacancies in the TM layers, which also occur in other oxygen redox compounds that exhibit oxygen loss such as Li[Li0.2Ni0.2Mn0.6]O-2, are not a trigger for oxygen loss. On charging at 5 V, P2-Na0.78Li0.25Mn0.75O2 exhibits oxygen loss, whereas P2-Na0.67Mg0.28Mn0.72O2 does not. Under these conditions, both Na+ and Li+ are removed from P2-Na0.78Li0.25Mn0.75O2, resulting in underbonded oxygen (fewer than 3 cations coordinating oxygen) and surface-localized O loss. In contrast, for P2-Na0.67Mg0.28Mn0.72O2, oxygen remains coordinated by at least 2 Mn4+ and 1 Mg2+ ions, stabilizing the oxygen and avoiding oxygen loss.
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| 33. |
- Källquist, Ida, et al.
(författare)
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Advances in studying interfacial reactions in rechargeable batteries by photoelectron spectroscopy
- 2022
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 10:37, s. 19466-19505
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Forskningsöversikt (refereegranskat)abstract
- Many of the challenges faced in the development of lithium-ion batteries (LIBs) and next-generation technologies stem from the (electro)chemical interactions between the electrolyte and electrodes during operation. It is at the electrode-electrolyte interfaces where ageing mechanisms can originate through, for example, the build-up of electrolyte decomposition products or the dissolution of metal ions. In pursuit of understanding these processes, X-ray photoelectron spectroscopy (XPS) has become one of the most important and powerful techniques in a large collection of available tools. As a highly surface-sensitive technique, it is often thought to be the most relevant in characterising the interfacial reactions that occur inside modern rechargeable batteries. This review tells the story of how XPS is employed in day-to-day battery research, as well as highlighting some of the most recent innovative in situ and operando methodologies developed to probe battery materials in ever greater detail. A large focus is placed not only on LIBs, but also on next-generation materials and future technologies, including sodium- and potassium-ion, multivalent, and solid-state batteries. The capabilities, limitations and practical considerations of XPS, particularly in relation to the investigation of battery materials, are discussed, and expectations for its use and development in the future are assessed.
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| 34. |
- Källquist, Ida, et al.
(författare)
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Degradation Mechanisms in Li2VO2F Li-Rich Disordered Rock-Salt Cathodes
- 2019
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 31:16, s. 6084-6096
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Tidskriftsartikel (refereegranskat)abstract
- The increased energy density in Li-ion batteries is particularly dependent on the cathode materials that so far have been limiting the overall battery performance. A new class of materials, Li-rich disordered rock salts, has recently been brought forward as promising candidates for next-generation cathodes because of their ability to reversibly cycle more than one Li-ion per transition metal. Several variants of these Li-rich cathode materials have been developed recently and show promising initial capacities, but challenges concerning capacity fade and voltage decay during cycling are yet to be overcome. Mechanisms behind the significant capacity fade of some materials must be understood to allow for the design of new materials in which detrimental reactions can be mitigated. In this study, the origin of the capacity fade in the Li-rich material Li2VO2F is investigated, and it is shown to begin with degradation of the particle surface that spreads inward with continued cycling.
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| 35. |
- Källquist, Ida, et al.
(författare)
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Influence of Electrolyte Additives on the Degradation of Li2VO2F Li-Rich Cathodes
- 2020
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Ingår i: The Journal of Physical Chemistry C. - : AMER CHEMICAL SOC. - 1932-7447 .- 1932-7455. ; 124:24, s. 12956-12967
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Tidskriftsartikel (refereegranskat)abstract
- rich disordered rock-salt structures have, because of their high theoretical capacity, gained a lot of attention as a promising class of cathode materials for battery applications. However, the cycling stability of these materials has so far been less satisfactory. Here, we present three different film-forming electrolyte additives: lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiODFB), and glycolide, which all improve the cycling performance of the high-capacity Li-rich disordered rock-salt material Li2VO2F. The best performing additive, LiODFB, shows a 12.5% increase of capacity retention after 20 cycles. The improved cycling performance is explained by the formation of a protective cathode interphase on the electrode surface. Photoelectron spectroscopy is used to show that the surface layer is created from degradation of the electrolyte salt and additive cosalts. The cathode interphase can mitigate oxidation and following degradation of the active material, and thereby a higher degree of redox-active vanadium can be maintained after 20 cycles.
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| 36. |
- Le Ruyet, Ronan, et al.
(författare)
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Electrochemical Sodiation and Desodiation of Gallium
- 2022
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 169:6
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Tidskriftsartikel (refereegranskat)abstract
- This study demonstrates the electrochemical sodiation and desodiation of gallium (Ga). A variety of techniques including galvanostatic cycling, cyclic voltammetry, as well as ex situ and in situ powder X-ray diffraction were used to determine the electrochemical reaction mechanisms. The sodiation and desodiation of Ga occurs reversibly at 0.71 V vs Na+/Na and the sodiated product was determined to be NaGa4 with a theoretical capacity of 96 mAh g(-1) (567 mAh cm(-3)). In addition, an anomalous plateau was observed at 0.66 V vs Na+/Na during the sodiation, which was attributed to a slow diffusion of Na into Ga particles. It was also shown that Na22Ga39 was not formed even if it is one of the expected compounds from the Ga-Na phases diagram. However, new crystalline structures were observed and were attributed to metastable phases of NaGa4.
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| 37. |
- Liberles, David A., et al.
(författare)
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The interface of protein structure, protein biophysics, and molecular evolution
- 2012
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Ingår i: Protein Science. - : Wiley. - 0961-8368 .- 1469-896X. ; 21:6, s. 769-785
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Forskningsöversikt (refereegranskat)abstract
- The interface of protein structural biology, protein biophysics, molecular evolution, and molecular population genetics forms the foundations for a mechanistic understanding of many aspects of protein biochemistry. Current efforts in interdisciplinary protein modeling are in their infancy and the state-of-the art of such models is described. Beyond the relationship between amino acid substitution and static protein structure, protein function, and corresponding organismal fitness, other considerations are also discussed. More complex mutational processes such as insertion and deletion and domain rearrangements and even circular permutations should be evaluated. The role of intrinsically disordered proteins is still controversial, but may be increasingly important to consider. Protein geometry and protein dynamics as a deviation from static considerations of protein structure are also important. Protein expression level is known to be a major determinant of evolutionary rate and several considerations including selection at the mRNA level and the role of interaction specificity are discussed. Lastly, the relationship between modeling and needed high-throughput experimental data as well as experimental examination of protein evolution using ancestral sequence resurrection and in vitro biochemistry are presented, towards an aim of ultimately generating better models for biological inference and prediction.
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| 38. |
- Liu, Haidong, et al.
(författare)
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Understanding the Roles of Tris(trimethylsilyl) Phosphite (TMSPi) in LiNi0.8Mn0.1Co0.1O2 (NMC811)/Silicon-Graphite (Si-Gr) Lithium-Ion Batteries
- 2020
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Ingår i: Advanced Materials Interfaces. - : WILEY. - 2196-7350. ; 7:15
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Tidskriftsartikel (refereegranskat)abstract
- The coupling of nickel-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes with high-capacity silicon-graphite (Si-Gr) anodes is one promising route to further increase the energy density of lithium-ion batteries. Practically, however, the cycle life of such cells is seriously hindered due to continuous electrolyte degradation on the surfaces of both electrodes. In this study, tris(trimethylsilyl) phosphite (TMSPi) is introduced as an electrolyte additive to improve the electrochemical performance of the NMC811/Si-Gr full cells through formation of protective surface layers at the electrode/electrolyte interfaces. This is thought to prevent the surface fluorination of the active materials and enhance interfacial stability. Notably, TMSPi is shown to significantly reduce the overpotential and operando X-ray diffraction (XRD) confirms that an irreversible "two-phase" transition reaction caused by the formed adventitious Li2CO3 layer on the surface of NMC811 can transfer to a solid-solution reaction mechanism with TMSPi-added electrolyte. Moreover, influences of TMSPi on the cathode electrolyte interphase (CEI) on the NMC811 and solid electrolyte interphase (SEI) on the Si-Gr are systematically investigated by electron microscopy and synchrotron-based X-ray photoelectron spectroscopy which allows for the nondestructive depth-profiling analysis of chemical compositions and oxidation states close to the electrode surfaces.
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| 39. |
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| 40. |
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