Both cationic and anionic redox chemistry in a P2-type sodium layered oxide

Journal Article · Fri Jan 10 00:00:00 EST 2020 · Nano Energy

DOI:https://doi.org/10.1016/j.nanoen.2020.104474· OSTI ID:1593270

Wang, Peng-Fei ^[1]; Xiao, Yao ^[2]; Piao, Nan  ^[1]; Wang, Qin-Chao ^[3]; Ji, Xiao ^[1]; Jin, Ting ^[1]; Guo, Yu-Jie ^[2]; Liu, Sufu ^[1]; Deng, Tao ^[1]; Cui, Chunyu ^[1]; Chen, Long ^[1]; Guo, Yu-Guo ^[2]; Yang, Xiao-Qing  ^[3]; Wang, Chunsheng ^[1]

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1. Univ. of Maryland, College Park, MD (United States)
2. Chinese Academy of Sciences (CAS), Beijing (China). CAS Key Laboratory of Molecular Nanostructure and Nanotechnology, CAS Research/Education Center for Excellence in Molecular Sciences, Beijing National Laboratory for Molecular Sciences (BNLMS), Inst. of Chemistry
3. Brookhaven National Lab. (BNL), Upton, NY (United States)

We report the demand for high energy Na-ion batteries has promoted intensive research on high energy oxygen redox chemistry in layered transition metal oxide cathodes. However, most layered cathodes with oxygen redox might suffer from irreversible electrochemical reaction, fast capacity decay and underlying O₂ release. Herein, we report that copper element with a strong electronegativaty can stablize Na-deficient P2-Na_2/3Mn_0.72Cu_0.22Mg_0.06O₂ phase to achieve both cationic and anionic redox chemistry. Hard and soft X-ray absorption spectra demonstrate that all Mn³⁺/Mn⁴⁺, Cu²⁺/Cu³⁺ and O^2-/(O₂)^n- participate in the redox reaction upon Na⁺ ions extraction and insertion. Density functional theory (DFT) calculations confirm that the strong covalency between copper and oxygen ensures the cationic and anionic redox activity in P2-Na_2/3Mn_0.72Cu_0.22Mg_0.06O₂ phase. The P2-Na_2/3Mn_0.72Cu_0.22Mg_0.06O₂ cathode could deliver stable cycling life with 87.9% capacity retention at 1C during 100 cycles, as well as high rate performance (70.3 mA h g^-1 cycled at 10C). In conclusion, our findings not only provide a promising guidelines to enhance the electrochemical performance of layered oxides based on anionic redox activity, but also explore the potential science behind oxygen redox process.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY (United States). National Synchrotron Light Source II (NSLS-II)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V); USDOE Office of Science (SC)
• Grant/Contract Number: SC0012704; EE0008202
• OSTI ID: 1593270
• Alternate ID(s): OSTI ID: 1592180
• Report Number(s): BNL-213544-2020-JAAM
• Journal Information: Nano Energy, Vol. 69, Issue C; ISSN 2211-2855
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

25 ENERGY STORAGE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Sodium-ion batteries
Cathode
Anionic redox
P2-type
Electrochemistry