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

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 Na0.5MnO2 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 Na0.5MnO2 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 Mn3.5+. 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 tomore » the strong interaction between the tunnel frame and inserted Na+ possessing a larger ionic size than inserted Li+.« less
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [2] ;  [2] ;  [2] ;  [2] ;  [6]
  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)
Publication Date:
OSTI Identifier:
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Nano Energy; Journal Volume: 19; Journal Issue: C
Research Org:
Argonne National Laboratory (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
30 DIRECT ENERGY CONVERSION; 77 NANOSCIENCE AND NANOTECHNOLOGY Alpha-MnO2; In situ TEM; Mn valence; Sodium ion battery; Tunnel