Dynamic study of (De)sodiation in alpha-MnO₂ nanowires

Journal Article · Fri Jan 01 00:00:00 EST 2016 · Nano Energy

DOI:https://doi.org/10.1016/j.nanoen.2015.11.028· OSTI ID:1247154

Yuan, Yifei ^[1]; Ma, Lu ^[2]; He, Kun ^[3]; Yao, Wentao ^[4]; Nie, Anmin ^[5]; Bi, Xuanxuan ^[2]; Amine, Khalil ^[2]; Wu, Tianpin ^[2]; Lu, Jun ^[2]; Shahbazian-Yassr, Reza ^[6]

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1. Michigan Technological Univ., Houghton, MI (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
2. Argonne National Lab. (ANL), Argonne, IL (United States)
3. Michigan Technological Univ., Houghton, MI (United States); Shandong Univ., Jinan (China)
4. Michigan Technological Univ., Houghton, MI (United States)
5. Univ. of Illinois, Chicago, IL (United States)
6. Michigan Technological Univ., Houghton, MI (United States); Univ. of Illinois, Chicago, IL (United States)

In this report, the electrochemical sodiation and desodiation in single crystalline alpha-MnO₂ nanowires are studied dynamically at both single particle level using in situ transmission electron microscopy (TEM) and bulk level using in situ synchrotron X-ray. The TEM results suggest that the first sodiation process starts with tunnel-based Na⁺ intercalation, experiences the formation of Na_0.5MnO₂ as a result of tunnel degradation, and ends with the Mn₂O₃ phase. The inserted Na⁺ can be partially extracted out of the sodiated products, and the following cycles are dominated by the reversible conversion reaction between Na_0.5MnO₂ and Mn₂O₃. The Mn valence evolution inside a cycling coin using alpha-MnO₂ nanowire electrode also exhibits partially reversible characteristic, agreeing well with the in situ TEM analysis. The sodiation is compared with lithiation in the same alpha-MnO₂ nanowires. Both Na⁺ and Li⁺ interact with the tunneled structure via a similar tunnel -driven intercalation mechanism before Mn⁴⁺ is reduced to Mn^3.5+. For the following deep insertion, the tunnels survive up. to LiMnO₂ (Mn3+) during lithiation, while the sodiation proceeds via a different mechanism that involves obvious phase transition and fast tunnel degradation after Mn's valence is below 3.5+. The difference in charge carrier insertion mechanisms can be ascribed to the strong interaction between the tunnel frame and inserted Na⁺ possessing a larger ionic size than inserted Li⁺.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States); Energy Frontier Research Centers (EFRC) (United States). Center for Electrical Energy Storage (CEES)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 1247154
• Journal Information: Nano Energy, Vol. 19, Issue C; ISSN 2211-2855
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

30 DIRECT ENERGY CONVERSION
77 NANOSCIENCE AND NANOTECHNOLOGY
Alpha-MnO2
In situ TEM
Mn valence
Sodium ion battery
Tunnel