Mn‐redox‐based oxides and oxyfluorides are considered the most promising earth‐abundant high‐energy cathode materials for next‐generation lithium‐ion batteries. While high capacities are obtained in high‐Mn content cathodes such as Li‐ and Mn‐rich layered and spinel‐type materials, local structure changes and structural distortions ( often lead to voltage fade, capacity decay, and impedance rise, resulting in unacceptable electrochemical performance upon cycling. In the present study, structural transformations that exploit the high capacity of Mn‐rich oxyfluorides while enabling stable cycling, in stark contrast to commonly observed structural changes that result in rapid performance degradation, are reported. It is shown that upon cycling of a cation‐disordered rocksalt (DRX) cathode (Li1.1Mn0.8Ti0.1O1.9F0.1, an ultrahigh capacity of ≈320 mAh g−1(energy density of ≈900 Wh kg−1) can be obtained through dynamic structural rearrangements upon cycling , along with a unique voltage profile evolution and capacity rise. At high voltage, the presence of Mn4+and Li+vacancies promotes local cation ordering, leading to the formation of domains of a “
Effects of Sodium and Magnesium Ions on the Photochemically Induced Heterogeneous Formation of Manganese Oxides and Their Structural Evolution
Manganese (Mn) oxides are abundant in aquatic and terrestrial environments, where they play significant roles in redox cycling and biological metabolisms. We recently observed that Mn oxides were homogenously formed during the abiotic oxidation of Mn2+(aq) to Mn(IV) by O2•− via nitrate photolysis, at a rate comparable to that of biotic Mn oxides formation. On the other hand, for the heterogeneous formation of Mn oxides, the presence of a substrate can alter the required thermodynamic driving force, which may affect their crystalline phases and further influence the oxidative capability of redox cycling in environmental systems. However, little is known about the photochemically-induced heterogeneous formation of Mn oxides on substrates. In this study, we investigated the heterogeneous formation of Mn oxides on a quartz substrate in the presence of two environmentally abundant cations, Na+ and Mg2+. In contrast to homogeneously generated Mn oxides, the heterogeneously formed Mn oxides displayed earlier crystalline phase evolutions and morphological changes over time. Additionally, the coexistence of Na+ and Mg2+ ions greatly affected the initial crystalline phase and the phase evolution, as well as the surface morphologies of the Mn oxides. These discoveries contribute to our understanding of how various Mn oxides form in nature and provide insight into the processes involved in manufacturing specific Mn oxide crystalline structures for engineering applications.
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- Award ID(s):
- 1905077
- PAR ID:
- 10482878
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- The Journal of Physical Chemistry C
- Volume:
- 127
- Issue:
- 26
- ISSN:
- 1932-7447
- Page Range / eLocation ID:
- 12558 to 12567
- Subject(s) / Keyword(s):
- Heterogenous nucleation Mn oxides tunnel structure Mg Na
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1021/acs.jpcc.3c00644
