Li_2MnSiO_4正极材料合成过程的热反应动力学

Thermal dynamics on synthesis of Li_2MnSiO_4 cathode materials

采用热重-差示扫描量热技术研究了高温固相法合成Li2MnSiO4正极材料的反应过程。结果表明:Li2MnSiO4前驱体在加热升温过程中的两个失重区主要归因于原料的脱水和分解;在不同升温速率条件下测得的差示扫描量热曲线主要由5个吸热峰组成;利用Doyle-Ozawa法和Kissinger法对前驱体分解失重阶段中三个吸热峰(>200℃)的反应活化能计算结果分别为:384.12、120.63、263.43 kJ/mol和350.78、117.16、227.59 kJ/mol;基于Kissinger法进一步确定了相关反应阶段的反应级数、频率因子和动力学速率方程。XRD测试说明:基于热力学结果的分步优化工艺能够减少终产物的杂质,改善合成质量。

Li2MnSiO4 cathode materials were synthesized by high temperature solid-state reaction. The synthesis process was investigated by thermogravimetric-differential scanning calorimetry （TG-DSC）. The results show that there are two main mass loss stages due to the dehydration and thermal decomposition of raw materials. There are five endothermic peaks appeared in DSC curves obtained at different heating rates. According to the thermal analysis, the apparent activate energy of three endothermic peaks （ 〉 200 ℃ ） is calculated to be 384. 12,120. 63, 263.43 kJ/mol and 350. 78, 117.16, 227.59 kJ/mol using the Doyle-Ozawa method and the Kissinger method, respectively. In the Kissinger method, the corresponding reaction order, frequency factor and reaction rate equation are further inferred. The results of X-ray diffraction （XRD） show the step-sintering method proposed from the thermal dynamics results can be used to produce better optimized-Li2 MnSiO4.