Journal
SMALL
Volume 18, Issue 6, Pages -Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/smll.202103499
Keywords
anionic frameworks; heavy fluorination; Li-ion batteries; lithium manganese layered oxide; reversible oxygen redox
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Funding
- Soft Science Research Project of Guangdong Province [2017B030301013]
- Shenzhen Science and Technology Research Grant [JCYJ20200109140416788]
- Chemistry and Chemical Engineering Guangdong Laboratory [1922018]
- National Key R&D Program of China [2020YFB0704500]
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The introduction of heavy fluorination into the layered anionic framework of a Li-Mn-O-F cathode has successfully inhibited the irreversible oxygen redox process, improved the reversibility of oxygen redox, and greatly enhanced the reversible capacity to nearly reach the theoretical capacity.
Lithium-excess manganese layered oxide Li2MnO3, attracts much attention as a cathode in Li-ion batteries, due to the low cost and the ultrahigh theoretical capacity (approximate to 460 mA h g(-1)). However, it delivers a low reversible practical capacity (<200 mA h g(-1)) due to the irreversible oxygen redox at high potentials (>4.5 V). Herein, heavy fluorination (9.5%) is successfully implemented in the layered anionic framework of a Li-Mn-O-F (LMOF) cathode through a unique ion-exchange route. F substitution with O stabilizes the layered anionic framework, completely inhibits the O-2 evolution during the first cycle, and greatly enhances the reversibility of oxygen redox, delivering an ultrahigh reversible capacity of 389 mA h g(-1), which is 85% of the theoretical capacity of Li2MnO3. Moreover, it also induces a thin spinel shell coherently forming on the particle surface, which greatly improves the surface structure stability, making LMOF exhibit a superior cycling stability (a capacity retention of 91.8% after 120 cycles at 50 mA g(-1)) and excellent rate capability. These findings stress the importance of stabilizing the anionic framework in developing high-performance low-cost cathodes for next-generation Li-ion batteries.
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