Morphology and mechanical behavior of composite electrodes for Li-ion batteries

Verma, Ankit

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https://hdl.handle.net/2142/42134 Copy

Description

Title

Morphology and mechanical behavior of composite electrodes for Li-ion batteries

Author(s)

Verma, Ankit

Issue Date

2012-12

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

Chasiotis, Ioannis

Department of Study

Aerospace Engineering

Discipline

Aerospace Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Lithium-ion batteries
• silicon electrode
• tin electrode
• solid electrolyte
• surface morphology study

Abstract

Electrochemical studies were conducted on thin-film composite silicon (Si) and tin (Sn) anodes and lithium cobalt oxide (LCO) structural cathodes for lithium ion (Li+) batteries. The composite electrodes were fabricated in the form of slurry with PVDF and carbon black as the matrix and the conductive agent, respectively, and were deposited and solidified on a copper (Cu) current collector. The interlaminar shear strength between the composite Si anode and the Cu current collector was found to be 1.27±0.75 MPa. The mechanical integrity of Si and Sn composite anodes was evaluated by cyclic lithiation/delithiation tests under galvanostatic and potentiostatic conditions. The charge rate (C/7 and C/30) and the Sn particle size (2-45 μm) were varied in the experiments. The anode surface was evaluated via post-mortem confocal laser imaging and scanning electron microscopy. It was found that a critical particle size of 5-8 µm dictated the onset of particle fracture and was independent of the charge rates used in this study. Compared to large particles, small Sn particles (<10 μm) resulted in higher initial discharge capacities, reaching up to 75% of the theoretical capacity. On the other hand, a fourfold reduction in charge rate increased the initial discharge capacity and improved on the capacity retention of large Sn particles that reached the capacity levels of small Sn particles. This low charge rate limited the formation of surface residue during electro-chemical testing, which contributed to the improved electrode performance. Finally, a complete solid-state battery was made from porous LCO and nickel-doped lithium titanate (Li4Ti5O12/Ni), infiltrated by a polymer electrolyte. The LCO half-cell was electrochemically and mechanically tested for an initial evaluation of this battery concept.

Graduation Semester

2012-12

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http://hdl.handle.net/2142/42134

Copyright and License Information

Copyright 2012 Ankit Verma

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