| 1. |
- Bowden, John A., et al.
(author)
-
Harmonizing lipidomics : NIST interlaboratory comparison exercise for lipidomics using SRM 1950-Metabolites in Frozen Human Plasma
- 2017
-
In: Journal of Lipid Research. - 0022-2275 .- 1539-7262. ; 58:12, s. 2275-2288
-
Journal article (peer-reviewed)abstract
- As the lipidomics field continues to advance, self-evaluation within the community is critical. Here, we performed an interlaboratory comparison exercise for lipidomics using Standard Reference Material (SRM) 1950-Metabolites in Frozen Human Plasma, a commercially available reference material. The interlaboratory study comprised 31 diverse laboratories, with each laboratory using a different lipidomics workflow. A total of 1,527 unique lipids were measured across all laboratories and consensus location estimates and associated uncertainties were determined for 339 of these lipids measured at the sum composition level by five or more participating laboratories. These evaluated lipids detected in SRM 1950 serve as community-wide benchmarks for intra-and interlaboratory quality control and method validation. These analyses were performed using nonstandardized laboratory-independent workflows. The consensus locations were also compared with a previous examination of SRM 1950 by the LIPID MAPS consortium.jlr While the central theme of the interlaboratory study was to provide values to help harmonize lipids, lipid mediators, and precursor measurements across the community, it was also initiated to stimulate a discussion regarding areas in need of improvement.
|
|
| 2. |
- House, Robert A., et al.
(author)
-
Lithium manganese oxyfluoride as a new cathode material exhibiting oxygen redox
- 2018
-
In: Energy & Environmental Science. - : Royal Society of Chemistry (RSC). - 1754-5692 .- 1754-5706. ; 11:4, s. 926-932
-
Journal article (peer-reviewed)abstract
- The quantity of charge stored in transition metal oxide intercalation cathodes for Li or Na batteries is not limited by transition metal redox reactions but can also access redox reactions on O; examples include Li1.2Ni0.13Mn0.54Co0.13O2, Li2Ru0.75Sn0.25O3, Li1.2Nb0.3Mn0.4O2, Na2RuO3 and Na2/3Mg0.28Mn0.72O2. Here we show that oxyfluorides can also exhibit charge storage by O-redox. We report the discovery of lithium manganese oxyfluoride, specifically the composition, Li1.9Mn0.95O2.05F0.95, with a high capacity to store charge of 280 mA h g(-1) (corresponding to 960 W h kg(-1)) of which almost half, 130 mA h g(-1), arises from O-redox. This material has a disordered cubic rocksalt structure and the voltage-composition curve is significantly more reversible compared with ordered Li-rich layered cathodes. Unlike lithium manganese oxides such as the ordered layered rocksalt Li2MnO3, Li1.9Mn0.95O2.05F0.95 does not exhibit O loss from the lattice. The material is synthesised using a simple, one-pot mechanochemical procedure.
|
|
| 3. |
- House, Robert A., et al.
(author)
-
Superstructure control of first-cycle voltage hysteresis in oxygen-redox cathodes
- 2020
-
In: Nature. - : NATURE PUBLISHING GROUP. - 0028-0836 .- 1476-4687. ; 577:7791, s. 502-508
-
Journal article (peer-reviewed)abstract
- In conventional intercalation cathodes, alkali metal ions can move in and out of a layered material with the charge being compensated for by reversible reduction and oxidation of the transition metal ions. If the cathode material used in a lithium-ion or sodium-ion battery is alkali-rich, this can increase the battery's energy density by storing charge on the oxide and the transition metal ions, rather than on the transition metal alone(1-10). There is a high voltage associated with oxidation of O2- during the first charge, but this is not recovered on discharge, resulting in reduced energy density(11). Displacement of transition metal ions into the alkali metal layers has been proposed to explain the first-cycle voltage loss (hysteresis)(9,12-16). By comparing two closely related intercalation cathodes, Na-0.75[Li0.25Mn0.75]O-2 and Na-0.6[Li0.2Mn0.8]O-2, here we show that the first-cycle voltage hysteresis is determined by the superstructure in the cathode, specifically the local ordering of lithium and transition metal ions in the transition metal layers. The honeycomb superstructure of Na-0.75[Li0.25Mn0.75]O-2, present in almost all oxygen-redox compounds, is lost on charging, driven in part by formation of molecular O-2 inside the solid. The O-2 molecules are cleaved on discharge, reforming O2-, but the manganese ions have migrated within the plane, changing the coordination around O2- and lowering the voltage on discharge. The ribbon superstructure in Na-0.6[Li0.2Mn0.8]O-2 inhibits manganese disorder and hence O-2 formation, suppressing hysteresis and promoting stable electron holes on O2- that are revealed by X-ray absorption spectroscopy. The results show that voltage hysteresis can be avoided in oxygen-redox cathodes by forming materials with a ribbon superstructure in the transition metal layers that suppresses migration of the transition metal. In oxygen-redox intercalation cathodes, voltage hysteresis can be avoided by forming cathode materials with a 'ribbon' superstructure in the transition metal layers that suppresses transition metal migration.
|
|
| 4. |
- House, Robert A., et al.
(author)
-
What Triggers Oxygen Loss in Oxygen Redox Cathode Materials?
- 2019
-
In: Chemistry of Materials. - : AMER CHEMICAL SOC. - 0897-4756 .- 1520-5002. ; 31:9, s. 3293-3300
-
Journal article (peer-reviewed)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.
|
|
| 5. |
- Maitra, Urmimala, et al.
(author)
-
Oxygen redox chemistry without excess alkali-metal ions in Na2/3[Mg0.28Mn0.72]O2
- 2018
-
In: Nature Chemistry. - : Springer Nature. - 1755-4330 .- 1755-4349. ; 10, s. 288-295
-
Journal article (peer-reviewed)abstract
- The search for improved energy-storage materials has revealed Li-and Na-rich intercalation compounds as promising high-capacity cathodes. They exhibit capacities in excess of what would be expected from alkali-ion removal/reinsertion and charge compensation by transition-metal (TM) ions. The additional capacity is provided through charge compensation by oxygen redox chemistry and some oxygen loss. It has been reported previously that oxygen redox occurs in O 2p orbitals that interact with alkali ions in the TM and alkali-ion layers (that is, oxygen redox occurs in compounds containing Li+-O(2p)-Li+ interactions). Na2/3[Mg0.28Mn0.72]O2 exhibits an excess capacity and here we show that this is caused by oxygen redox, even though Mg2+ resides in the TM layers rather than alkali-metal (AM) ions, which demonstrates that excess AM ions are not required to activate oxygen redox. We also show that, unlike the alkali-rich compounds, Na2/3[Mg0.28Mn0.72]O2 does not lose oxygen. The extraction of alkali ions from the alkali and TM layers in the alkalirich compounds results in severely underbonded oxygen, which promotes oxygen loss, whereas Mg2+ remains in Na2/3[Mg0.28Mn0.72]O2, which stabilizes oxygen.
|
|
| 6. |
- Somerville, James W., et al.
(author)
-
Nature of the "Z"-phase in layered Na-ion battery cathodes
- 2019
-
In: Energy & Environmental Science. - : ROYAL SOC CHEMISTRY. - 1754-5692 .- 1754-5706. ; 12:7, s. 2223-2232
-
Journal article (peer-reviewed)abstract
- Layered sodium transition metal oxides with the P2 structure, e.g. Na-2/3[Ni1/3Mn2/3]O-2, are regarded as candidates for Na-ion battery cathodes. On charging, extraction of Na destabilizes the P2 phase (ABBA oxide ion stacking) in which Na+ is in trigonal prismatic coordination, resulting in layer gliding and formation of an O2 phase (ABAC stacking) with octahedral coordination. However, many related compounds do not exhibit such a simple P2 to O2 transition but rather form a so called Z-phase. Substituting Ni by Fe in Na-2/3[Ni1/3Mn2/3]O-2 is attractive as it reduces cost. The Fe containing compounds, such as Na-2/3[Ni1/6Mn1/2Fe1/3]O-2, form a Z-phase when charged above 4.1 V vs. Na+/Na. By combining ex situ and operando X-ray diffraction with scanning transmission electron microscopy and simulated diffraction patterns, we demonstrate that the Z-phase is most accurately described as a continuously changing intergrowth structure which evolves from P2 to O2 through the OP4 structure as an intermediate. On charging, Na+ removal results in O-type stacking faults within the P2 structure which increase in proportion. At 50% O-type stacking faults, the ordered OP4 phase forms and on further charging more O-type stacking faults are formed progressing towards a pure O2 structure. This gives the superficial appearance of a solid solution. Furthermore, in contrast to some previous studies, we did not detect Fe migration at any state-of-charge using Fe-57-Mossbauer spectroscopy. It was, however, found that the Fe-substitution serves to disrupt cation ordering in the material.
|
|
| 7. |
- Thomson, Amanda, et al.
(author)
-
The Ussing chamber system for measuring intestinal permeability in health and disease
- 2019
-
In: BMC Gastroenterology. - : BMC. - 1471-230X. ; 19
-
Journal article (peer-reviewed)abstract
- BackgroundThe relationship between intestinal epithelial integrity and the development of intestinal disease is of increasing interest. A reduction in mucosal integrity has been associated with ulcerative colitis, Crohns disease and potentially could have links with colorectal cancer development. The Ussing chamber system can be utilised as a valuable tool for measuring gut integrity. Here we describe step-by-step methodology required to measure intestinal permeability of both mouse and human colonic tissue samples ex vivo, using the latest equipment and software. This system can be modified to accommodate other tissues.MethodsAn Ussing chamber was constructed and adapted to support both mouse and human tissue to measure intestinal permeability, using paracellular flux and electrical measurements. Two mouse models of intestinal inflammation (dextran sodium sulphate treatment and T regulatory cell depletion using C57BL/6-FoxP3(DTR) mice) were used to validate the system along with human colonic biopsy samples.ResultsDistinct regional differences in permeability were consistently identified within mouse and healthy human colon. In particular, mice showed increased permeability in the mid colonic region. In humans the left colon is more permeable than the right. Furthermore, inflammatory conditions induced chemically or due to autoimmunity reduced intestinal integrity, validating the use of the system.ConclusionsThe Ussing chamber has been used for many years to measure barrier function. However, a clear and informative methods paper describing the setup of modern equipment and step-by-step procedure to measure mouse and human intestinal permeability isnt available. The Ussing chamber system methodology we describe provides such detail to guide investigation of gut integrity.
|
|
