Publication Date

2011

Document Type

Thesis

Committee Members

Kuan-lun Chu (Advisor), Hong Huang (Advisor), Yan Zhuang (Committee Chair)

Degree Name

Master of Science in Engineering (MSEgr)

Abstract

Porous silicon (PS) membranes for lithium-ion batteries (LIBs) anode applications were developed, demonstrated and characterized systematically in this work. Electrochemical measurements were conducted on both Si-wafer supported and free-standing porous Si membranes. It turned out that the specific capacity of LIBs was enhanced remarkably by PS based anode. PS was fabricated by using electrochemical anodization in a mixed solution of Dimethylformamide (DMF) and Hydrofluoric acid (HF wt.49%). By varying the anodization conditions, including HF concentration, anodization etching time and current density, pores were formed in a p-type (1-20Ω cm) boron-doped silicon substrate. Scanning electron microscopy (SEM) was employed to investigate the surface morphology of the pores (pore distribution, diameter and depth). The electrochemical agglomeration was observed on the wall of the pores (WOPs). The surface percentage of WOPs was calculated by Finite Element Analysis (OOF2). It turned out that the 27.5 % of the surface is occupied by the WOPs, and the average diameters of the pores are in the range between 0.85μm to 1.53μm. The Li insertion in the porous silicon was investigated by cyclic voltammetry method (CV) as well as the small constant current discharge/charge analysis. As increase of the depth of the pores, the specific capacity increased due to the enlarged surface area. The PS anode with 89.4μm of depth showed high cycling stability, manifested by the unchanged porous structure after 10 charge-discharge cycles. The specific capacity up to 1150mAh/g was achieved.

Page Count

97

Department or Program

Department of Electrical Engineering

Year Degree Awarded

2011

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