Synthesis and Non-isothermal Kinetic Analysis of Li-ion Secondary Battery Cathode Material Nano-Lithium Iron Phosphate Composite
Date Issued
2004
Date
2004
Author(s)
Chang, Hao-Hsun
DOI
zh-TW
Abstract
Compared with the oxide electrode materials currently used for the lithium ion battery, LiFePO4 has the advantages of lower cost, high stability, and environmentally friendly. Hence, it is considered as a good candidate of positive electrode material. The thesis is mainly on the synthesis of composite positive electrode material of nano LiFePO4/carbon black with high conductivity.
In this report, nano LiFePO4/carbon black is synthesized through solid state method and liquid phase method. The investigation agenda of the synthesis conditions include the selection of atmosphere, conversion via quantitative analysis, the effecting factors of conversion, tendency of crystal size, and the comparison.
On choosing reaction atmosphere, the experimental data indicate that the best one is that with 1%H2（99%N2）, whereas impurity is incurred with excess or insufficient gas. Through analysis, it is found that the conversion of each approach quickly arrives to its own constant value under various sintering temperatures. It has no effect for improving the conversion even prolonging the sintering time. It implies that the principal factor affecting the conversion rate is the sintering temperature rather than the sintering time.
Nevertheless, the crystal size tends to agglomerate with the sintering time. A scanning electron microscope (SEM) is used to examine the synthesized powder. Powder made by the solid-state method shows aggregates of micro-scale crystals, whereas powder of liquid phase approach is tightly adhered by carbon black. From comparison of meticulous conditions, as well as the survey of batch-wise preparations, it is concluded that the “liquid phase approach” is the better choice of the two methods. It can provide nano crystals of less than 100nm under 700℃.
Moreover, the thesis presents a non-isothermal kinetic analysis of the synthesis of LiFePO4, where three dimensional nuclei growth is found to be the reaction limiting mechanism.
Cyclic voltametry and charge-discharge cycle test was applied to perform the electrochemical test. In the result, LFPO via liquid method revealed capacity of 85mAh/g at C-rate 1C-1C, and 110mAh/g at 0.1C-0.1C.
Subjects
動力學
製備
鋰鐵磷酸鹽
正極材料
鋰離子電池
Cathode material
LiFePO4
Lithium-ion battery
Kinetics
SDGs
Type
thesis
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