Llusco Aleksei, Grageda Mario, Ushak Svetlana
Departamento de Ingeniería Química y Procesos de Minerales and Center for Advanced Study of Lithium and Industrial Minerals (CELiMIN), Universidad de Antofagasta, Campus Coloso, Av Universidad de Antofagasta, 02800 Antofagasta, Chile.
Nanomaterials (Basel). 2020 Jul 19;10(7):1409. doi: 10.3390/nano10071409.
In this work, a first study on kinetics and thermodynamics of thermal decomposition for synthesis of doped LiMnO nanoparticles is presented. The effect of Mg doping concentration on thermal decomposition of synthesis precursors, prepared by ultrasound-assisted Pechini-type sol-gel process, and its significance on nucleation and growth of Mg-doped LiMnO nanoparticles was studied through a method based on separation of multistage processes in single-stage reactions by deconvolution and transition state theory. Four zones of thermal decomposition were identified: Dehydration, polymeric matrix decomposition, carbonate decomposition and spinel formation, and spinel decomposition. Kinetic and thermodynamic analysis focused on the second zone. First-order Avrami-Erofeev equation was selected as reaction model representing the polymer matrix thermal decomposition. Kinetic and thermodynamic parameters revealed that Mg doping causes an increase in thermal inertia on conversion rate, and CO desorption was the limiting step for formation of thermodynamically stable spinel phases. Based on thermogravimetry experiments and the effect of Mg on thermal decomposition, an optimal two-stage heat treatment was determined for preparation of LiMgMnO (x = 0.00, 0.02, 0.05, 0.10) nanocrystalline powders as promising cathode materials for lithium-ion batteries. Crystalline structure, morphology, and stoichiometry of synthesized powders were characterized by XRD, FE-SEM, and AAS, respectively.
在这项工作中，首次对用于合成掺杂锂锰氧化物纳米颗粒的热分解动力学和热力学进行了研究。通过一种基于去卷积和过渡态理论将单阶段反应中的多阶段过程分离的方法，研究了镁掺杂浓度对通过超声辅助佩琴尼型溶胶 - 凝胶法制备的合成前驱体热分解的影响，以及其对掺杂镁的锂锰氧化物纳米颗粒成核和生长的意义。确定了热分解的四个区域：脱水、聚合物基体分解、碳酸盐分解和尖晶石形成以及尖晶石分解。动力学和热力学分析集中在第二个区域。选择一阶阿弗拉米 - 埃罗费耶夫方程作为代表聚合物基体热分解的反应模型。动力学和热力学参数表明，镁掺杂导致转化率的热惯性增加，并且CO脱附是形成热力学稳定尖晶石相的限制步骤。基于热重实验和镁对热分解的影响，确定了一种用于制备LiMgMnO（x = 0.00、0.02、0.05、0.10）纳米晶粉末的最佳两阶段热处理方法，这些粉末有望作为锂离子电池的阴极材料。分别通过XRD、FE - SEM和AAS对合成粉末的晶体结构、形态和化学计量进行了表征。
