Non-isothermal kinetics study on synthesis of LiFePO4 via carbothermal reduction method

作者：He, Lihua; Liu, Xuheng; Zhao, Zhongwei^*

来源：Thermochimica Acta, 2013, 566: 298-304.

DOI：10.1016/j.tca.2013.06.014

• Lithium iron phosphate
• Thermal kinetics
• Avrami
• Carbothermal reduction

Non-isothermal kinetics of lithium ion phosphate synthesis via carbothermal reduction method with raw materials Li2CO3, FePO4 center dot 2H(2)O and C6H12O6 center dot 2H(2)O is studied by thermogravimetry-differential scanning calorimetry (TG-DSC) technology. The results indicate the synthesis process can be divided into two stages: dehydration and LiFePO4 formation. The apparent activation energy and natural logarithm frequency factor (In A-value) for dehydration reaction is respectively 83.4 +/- 4.7 kJ mol(-1) and 22.1 +/- 1.5 s(-1), and that for LiFePO4 formation reaction is in turn 184.2 +/- 10.4 kJ mol(-1) and 28.3 +/- 1.9 s(-1). Additionally, the mechanism for dehydration and LiFePO4 formation stages is Avrami's A(1.5) and A(4), respectively. Furthermore, the dehydration process is diffusion controlled, and the crystallization of LiFePO4 formation is controlled by nuclei being formed randomly and growing in three-dimensions, and the kinetic equations for each stage are shown as follows:
Dehydration stage : [-ln(1 - a)](2/3) = 3.96 x 10(9) exp (-8.34 x 10(4)/RT) t;
LiFePO4 formation stage : [-ln(1 - a)](1/4) = 1.95 x 10(12) exp (-1.84 x 10(5)/RT) t;
where a is the fractional conversion, T the calcination temperature (K), t the calcination time (s), R the gas constant (8.314J mol(-1) K-1).

• 出版日期2013-8-20
• 单位中南大学