Publication Date
2012
Document Type
Thesis
Committee Members
Hong Huang (Advisor), Bor Z. Jang (Committee Member), H. Daniel Young (Committee Member)
Degree Name
Master of Science in Engineering (MSEgr)
Abstract
Olivine structured LiFePO4 is a promising cathode material for the next generation of lithium ion batteries for its low cost, environmental benign, good cycling performance and safety, etc. However, its intrinsic poor electrical conductivity and diffusion capability of lithium ion greatly hinder its application in the high power recharge battery. In this research, a cost-effective sol-gel method was used to synthesize carbon coated LiFePO4 (LiFePO4/C) materials. The influences of the synthesis parameters, including the species of iron source, lithium content, chelating agents and carbon sources, PH value of the sol, and sintering conditions etc., on the structure and electrochemical properties of the LiFePO4/C were investigated by means of X-ray diffraction (XRD), Scanning electron microscope (SEM), galvanostatic charge-discharge and electrochemical impedance spectroscopy. Nanocrystalline LiFePO4/C materials with spherical particles of less than 500nm and appropriate amount of carbon coating are successfully obtained after optimizing the synthesis parameters. Maximum capacity of 152mAh/g was achieved at 0.2C rate, in addition to long cycle life (over 150 cycles) and good discharge rate capability (120mAh/g at the 2C rate). Further, the impact of stability of complexing compounds on the electrochemical properties, carbon contents and the mircrostructure of the LiFePO4 products were discussed based on the coordination chemistry principle.
Page Count
124
Department or Program
Department of Mechanical and Materials Engineering
Year Degree Awarded
2012
Copyright
Copyright 2012, all rights reserved. This open access ETD is published by Wright State University and OhioLINK.
