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- Morozov, Anatolii V., et al.
(författare)
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Retardation of Structure Densification by Increasing Covalency in Li-Rich Layered Oxide Positive Electrodes for Li-Ion Batteries
- 2022
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 34:15, s. 6779-6791
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Tidskriftsartikel (refereegranskat)abstract
- Because of the outstanding discharge capacity provided by oxygen redox activity, Li-rich layered oxide positive electrode materials for Li-ion batteries attract tremendous attention. However, there is still no full consensus on the role that the ionocovalency of transition metal (TM)–oxygen (O) chemical bonding plays in the reversibility of the oxygen redox as well as on both local crystal and electronic structure transformations. Here, we managed to tune the cationic/anionic redox contributions to the overall electrochemical activity using the xLi2RuO3-(1 – x)Li1.2Ni0.2Mn0.6O2 solid solutions as a model system possessing the same crystal structure and morphology as Li-rich layered oxides. We conclusively traced the whole cascade of events from increasing the covalency of the TM–O bond, suppressing irreversible oxygen oxidation to the generation of the reduced Mn species toward retarding the structure “densification” in the Li-rich layered oxides. The results demonstrate that enhancing the degree of covalency of the TM–O bonding is vitally important for anchoring the reversibility of the charge compensation mechanism occurring through partial oxygen oxidation.
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| 2. |
- Williams, Charles J. R., et al.
(författare)
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African Hydroclimate During the Early Eocene From the DeepMIP Simulations
- 2022
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Ingår i: Paleoceanography and Paleoclimatology. - 2572-4517 .- 2572-4525. ; 37:5
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Tidskriftsartikel (refereegranskat)abstract
- The early Eocene (∼56–48 Myr ago) is characterized by high CO2 estimates (1,200–2,500 ppmv) and elevated global temperatures (∼10°C–16°C higher than modern). However, the response of the hydrological cycle during the early Eocene is poorly constrained, especially in regions with sparse data coverage (e.g., Africa). Here, we present a study of African hydroclimate during the early Eocene, as simulated by an ensemble of state-of-the-art climate models in the Deep-time Model Intercomparison Project (DeepMIP). A comparison between the DeepMIP pre-industrial simulations and modern observations suggests that model biases are model- and geographically dependent, however, these biases are reduced in the model ensemble mean. A comparison between the Eocene simulations and the pre-industrial suggests that there is no obvious wetting or drying trend as the CO2 increases. The results suggest that changes to the land sea mask (relative to modern) in the models may be responsible for the simulated increases in precipitation to the north of Eocene Africa. There is an increase in precipitation over equatorial and West Africa and associated drying over northern Africa as CO2 rises. There are also important dynamical changes, with evidence that anticyclonic low-level circulation is replaced by increased south-westerly flow at high CO2 levels. Lastly, a model-data comparison using newly compiled quantitative climate estimates from paleobotanical proxy data suggests a marginally better fit with the reconstructions at lower levels of CO2.
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