Structural evolution of α-Fe2O3 nanowires during lithiation/delithiation and electrochemical property improvement

Huang, Bo

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https://hdl.handle.net/2142/44162 Copy

Description

Title

Structural evolution of α-Fe2O3 nanowires during lithiation/delithiation and electrochemical property improvement

Author(s)

Huang, Bo

Issue Date

2013-05-24T21:53:03Z

Director of Research (if dissertation) or Advisor (if thesis)

Dillon, Shen J.

Department of Study

Materials Science & Engineerng

Discipline

Materials Science & Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Conversion Reaction
• Mechanism
• Lithium Ion Battery
• Nanowires

Abstract

Hematite Fe2O3 exhibits great potential in lithium ion battery area as anode material, due to high capacity, elemental abundance, low cost and biocompatibility. Its reaction with lithium ion is accepted as conversion reaction. In this paper, single crystal α-Fe2O3 nanowires were prepared by an electrical resistive heating method under ambient conditions. Transmission electron microscopy characterized the anode material at various stages of lithiation and delithiation. The phase and morphological evolution demonstrate the conversion reaction process in α-Fe2O3. The process was initiated through the reduction of Fe2O3 to Fe3O4 nanocrystals, which form 4-nm-nanoparticles within the nanowire. Further lithiation converted all of the iron oxides to BCC Fe nanocrystals with the significant growth up to 21 nm. During delithiation, the reactions proceeded in the reverse order, Fe0-Fe2+-Fe3+. However, the initial single crystalline α-Fe2O3 nanowires were replaced by nanocrystalline ones after first cycle. The delithiated electrode maintains the nanowire geometry over many cycles due to the nature of the short-range cation diffusion that facilitates the process. Besides, nanowires covered with continuous carbon film exhibited much better electrochemical properties, such as cycle capacity, stability and conductivity, than the uncoated ones. The intrinsic conductivity improvement from α-Fe2O3 to Fe3O4 can further enhance the electrochemical performance.

Graduation Semester

2013-05

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http://hdl.handle.net/2142/44162

Copyright and License Information

Copyright 2013 Bo Huang

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