Date of Graduation

5-2018

Document Type

Thesis

Degree Name

Master of Science in Microelectronics-Photonics (MS)

Degree Level

Graduate

Department

Microelectronics-Photonics

Advisor/Mentor

Ang, Simon S.

Committee Member

Tian, Z. Ryan

Second Committee Member

Zhao, Yue

Third Committee Member

Wise, Rick L.

Keywords

Graphene; Lithium Cobalt Oxide; Lithium Ion Batteries

Abstract

One of the objectives of this thesis work was to investigate the cathode performance of lithium cobalt oxide (LiCoO2) incorporated with graphene powder in lithium ion batteries (LIBs). Graphene powder was incorporated into cathode materials to enhance the performance of LIBs. The other objective was to impede the construction of a solid electrolyte interphase (SEI) sheet using graphene sheet coating on its cathode.

The results of this work show that adding graphene powder improved the performance of LiCoO¬2 as a cathode material. With the incorporation of different weight percentages of graphene powder, the LiBs showed distinct changes in their charging and discharging characteristics. The cell with its cathode incorporated with a 0.5 wt.% graphene powder exhibited the highest discharge capacity at currents 0.1 C and 0.5 C, The incorporation of 1 wt.% graphene powder contributed the most stable performance of the cathode at currents from 0.1 C to 2 C. In addition, the cell with its cathode incorporated with 2 wt.% graphene powder exhibited a higher discharge capacity of the cathode.

Conversely, the cathodes coated with one graphene sheet exhibited lower discharge capacity than that of the pristine cathode. This can be explained by the transfer limit of lithium ions as the graphene sheet blocked the electrolyte immersing into cathode materials, thus only part of cathode materials participate in the process of lithium ion transfer.

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