1
|
Abulikemu A, Matsunaga T, Shi X, Kumar M, Thakur N, Takami T, Yamamoto K, Uchiyama T, Watanabe T, Inada M, Uchimoto Y. Improving the Cyclic Reversibility of Layered Li-Rich Cathodes by Combining Oxygen Vacancies and Surface Fluorination. ACS Appl Mater Interfaces 2023; 15:54419-54431. [PMID: 37967338 DOI: 10.1021/acsami.3c11511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2023]
Abstract
Layered-type Li-rich cathode materials have attracted significant attention for next-generation Li-ion batteries, but the advantage of their high capacity is eclipsed by their poor reversibility upon cycling. Irreversible oxygen redox activity and surface degradation have been deemed as the root cause and direct cause for their poor performance, respectively. We attempted to suppress surface degradation by inserting fluoride ions up to some depth on the surface. By fluorination with NH4HF2 after introducing a significant amount of oxygen vacancies in layered Li1.2Ni0.2Co0.2Mn0.4O2 by using CaH2 as a reducing agent, the reversible capacity reached 268 mAh/g, and the capacity retention after 100 cycles was about 99%. The scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS) technique revealed that, in contrast to directly fluorinated samples, our materials exhibit deeper fluorine signals besides surface signals, and hard X-ray photoelectron spectroscopy (HAXPES) patterns show ionic and covalent fluorine coordination. These results indicate that the combination of oxygen deficiency introduction and surface fluorination allows some F- ions to occupy near-surface oxygen vacancy sites rather than forming only a LiF layer on the surface, suggesting a new strategy to modify cathode materials for lithium-ion batteries.
Collapse
Affiliation(s)
- Aierxiding Abulikemu
- Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Toshiyuki Matsunaga
- Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Xian Shi
- Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Mukesh Kumar
- Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Neha Thakur
- Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Tsuyoshi Takami
- Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Kentaro Yamamoto
- Faculty of Engineering, Nara Women's University, Kita-uoya Nishimachi, Nara 630-8506, Japan
| | - Tomoki Uchiyama
- Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Toshiki Watanabe
- Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Miki Inada
- Center of Advanced Instrumental Analysis, Kyushu University, Fukuoka 819-0395, Japan
| | - Yoshiharu Uchimoto
- Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| |
Collapse
|
2
|
Ma C, Abulikemu A, Bao J, Uchiyama T, Xia YY, Li XL, Uchimoto Y, Zhou YN. Stacking Order Induced Anion Redox Regulation for Layer-Structured Na 0.75 Li 0.2 Mn 0.7 Cu 0.1 O 2 Cathode Materials. Small 2023; 19:e2302332. [PMID: 37140106 DOI: 10.1002/smll.202302332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2023] [Revised: 04/17/2023] [Indexed: 05/05/2023]
Abstract
Stacking order plays a key role in defining the electrochemical behavior and structural stability of layer-structured cathode materials. However, the detailed effects of stacking order on anionic redox in layer-structured cathode materials have not been investigated specifically and are still unrevealed. Herein, two layered cathodes with the same chemical formula but different stacking orders: P2-Na0.75 Li0.2 Mn0.7 Cu0.1 O2 (P2-LMC) and P3-Na0.75 Li0.2 Mn0.7 Cu0.1 O2 (P3-LMC) are compared. It is found that P3 stacking order is beneficial to improve the oxygen redox reversibility compared with P2 stacking order. By using synchrotron hard and soft X-ray absorption spectroscopies, three redox couples of Cu2+ /Cu3+ , Mn3.5+ /Mn4+ , and O2- /O- are revealed to contribute charge compensation in P3 structure simultaneously, and two redox couples of Cu2+ /Cu3+ and O2- /O- are more reversible than those in P2-LMC due to the higher electronic densities in Cu 3d and O 2p orbitals in P3-LMC. In situ X-ray diffraction reveals that P3-LMC exhibits higher structural reversibility during charge and discharge than P2-LMC, even at 5C rate. As a result, P3-LMC delivers a high reversible capacity of 190.3 mAh g-1 and capacity retention of 125.7 mAh g-1 over 100 cycles. These findings provide new insight into oxygen-redox-involved layered cathode materials for SIBs.
Collapse
Affiliation(s)
- Cui Ma
- Department of Materials Science, Fudan University, Shanghai, 200438, China
| | - Aierxiding Abulikemu
- Department of Interdisciplinary Environment, Kyoto University, Kyoto, 606-8501, Japan
| | - Jian Bao
- Department of Materials Science, Fudan University, Shanghai, 200438, China
| | - Tomoki Uchiyama
- Department of Interdisciplinary Environment, Kyoto University, Kyoto, 606-8501, Japan
| | - Yong-Yao Xia
- Department of Chemistry, Fudan University, Shanghai, 200438, China
| | - Xun-Lu Li
- Department of Materials Science, Fudan University, Shanghai, 200438, China
- Global Institute of Future Technology, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Yoshiharu Uchimoto
- Department of Interdisciplinary Environment, Kyoto University, Kyoto, 606-8501, Japan
| | - Yong-Ning Zhou
- Department of Materials Science, Fudan University, Shanghai, 200438, China
| |
Collapse
|