Title: Stabilizing Transition Metal Vacancy Induced Oxygen Redox by Co²⁺/Co³⁺ Redox and Sodium-Site Doping for Layered Cathode Materials

Abstract

Anionic redox is an effective way to boost the energy density of layer-structured metal-oxide cathodes for rechargeable batteries. However, inherent rigid nature of the TMO₆ (TM: transition metals) subunits in the layered materials makes it hardly tolerate the inner strains induced by lattice glide, especially at high voltage. Herein, P2-Na_0.8Mg0.13[Mn_0.6Co_0.2Mg_{0.07$$\square$$0.13}]O₂ ($$\square$$: TM vacancy) is designed that contains vacancies in TM sites, and Mg ions in both TM and sodium sites. Vacancies make the rigid TMO₆ octahedron become more asymmetric and flexible. Low valence Co²⁺/Co³⁺ redox couple stabilizes the electronic structure, especially at the charged state. Mg²⁺ in sodium sites can tune the interlayer spacing against O-O electrostatic repulsion. Time-resolved in situ X-ray diffraction confirms that irreversible structure evolution is effectively suppressed during deep desodiation benefiting from the specific configuration. X-ray absorption spectroscopy (XAS) and density functional theory (DFT) calculations demonstrate that, deriving from the intrinsic vacancies, multiple local configurations of “_$$\square$$-O-_$$\square$$”, “Na-O-_$$\square$$”, “Mg-O-_$$\square$$” are superior in facilitating the oxygen redox for charge compensation than previously reported “Na-O-Mg”. The resulted material delivers promising cycle stability and rate capability, with a long voltage plateau at 4.2 V contributed by oxygen, and can be well maintained even at high rates. The strategy will inspire new ideas in designing highly stable cathode materials with reversible anionic redox for sodium-ion batteries.

Authors:

Li, Xun‐Lu  ^[1];

• Search DOE PAGES for author "Li, Xun‐Lu"
• Search DOE PAGES for ORCID "0000-0002-7800-3565"
• Search orcid.org for ORCID "0000-0002-7800-3565"

Bao, Jian ^[1]; Shadike, Zulipiya ^[2]; Wang, Qin‐Chao ^[1]; Yang, Xiao‐Qing  ^[3];

• Search DOE PAGES for author "Yang, Xiao‐Qing"
• Search DOE PAGES for ORCID "0000-0002-3625-3478"
• Search orcid.org for ORCID "0000-0002-3625-3478"

Zhou, Yong‐Ning  ^[1];

• Search DOE PAGES for author "Zhou, Yong‐Ning"
• Search DOE PAGES for ORCID "0000-0002-9791-3468"
• Search orcid.org for ORCID "0000-0002-9791-3468"

Sun, Dalin ^[1]; Fang, Fang ^[1]

---

+ Show Author Affiliations

1. Fudan Univ., Shanghai (China)
2. Shanghai Jiao Tong Univ. (China)
3. Brookhaven National Lab. (BNL), Upton, NY (United States)

Publication Date:

2021-08-10

Research Org.:

Brookhaven National Lab. (BNL), Upton, NY (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE), Transportation Office. Vehicle Technologies Office; National Natural Science Foundation of China (NSFC); Science & Technology Commission of Shanghai Municipality; National Key Research and Development Program of China; China Postdoctoral Science Foundation; Zhuhai Fudan Innovation Institute

OSTI Identifier:

1820169

Report Number(s):

BNL-222094-2021-JAAM
Journal ID: ISSN 1433-7851

Grant/Contract Number:  

SC0012704

Resource Type:

Accepted Manuscript

Journal Name:

Angewandte Chemie (International Edition)

Additional Journal Information:

Journal Name: Angewandte Chemie (International Edition); Journal Volume: 60; Journal Issue: 40; Journal ID: ISSN 1433-7851

Publisher:

Wiley

Country of Publication:

United States

Language:

English

Subject:

25 ENERGY STORAGE; cathode materials; intrinsic vacancies; oxygen redox; sodium sites; sodium-ion batteries