Date of Award

May 2016

Degree Type

Thesis

Degree Name

Master of Science

Department

Engineering

First Advisor

Junjie Niu

Committee Members

Yin Wang, Benjamin C. Church

Abstract

Lithium-ion batteries have been widely used for many years. The wide application covers such as smart phones, laptops, digital cameras, MP3 players, and electric vehicles. Lithium-ion batteries have become the most important energy storage device in the future. For lithium-ion batteries, the performance of the cathode materials is one of the most important factors. In recent years, the cathode materials have been widely studied including LiCoO2, LiNiO2, LiMnO2, LiMn2O4 and phosphate etc. Among the olivine structure cathode materials, the LiFePO4 (LFP) displays an excellent electrochemical activity and a chemical stability which ensure a high safety. In order to better improve the battery performance, a thorough understanding of phase transformation during the charge/discharge in real time poses a critical issue on this promising battery. Here we applied a template-assisted CVD method to synthesize LFP nanomaterials. In this experiment, we aim to synthesize nano-sized hollow sphere LFP/C structure. LiC2H3O2·2H2O (Sigma-Aldrich), Fe(NO3)3·9H2O (Sigma-Aldrich), H3PO4 (Sigma-Aldrich) are used as the reactants. Colloidal silica (Nissan Chemical) is used as the nano-sized sphere template. The sucrose (Sigma-Aldrich) is used as the source of the carbon. The collison nebulizer (BGI) is used to spray the aqueous solution as liquid drop state into the tube furnace. Under the argon flow, black powders are collected using the filter holder (VWR). After annealing, LFP is collected. Then removing the SiO2 template is an important step. A variety of characterizations (XRD, SEM, TEM), electrochemical measurements and transmission X-ray microscopy (TXM) have been used to test the cathode materials.

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