T型微反应器共沉淀法制备锂离子电池多孔MnO/C 微球负极材料

Coprecipitation method in T-type microreactor is a new effective way to prepare porous MnO/C microspheres with good electrochemical performance. And the ability to control the spherical porous structure to obtain the desired electrochemical properties is the key for this method to success. This project will focus on investigating the critical problem of controlling the spherical porous structure and solve it. . First, effects of the preparation processes on the formation of porous MnO/C microspheres will have been investigated. These results will be used to identify the formation mechanism of porous MnO/C microspheres, and determine the　nucleation-growth model of precursors in T-type microreactor and the kinetic model for precursors transformation during the heat treatment processes.. Second, the principles and methodologies of heterogeneous reaction will be applied to investigate the Kinetic models for the formation processes of spherical porous structure of the precursors and MnO/C. And the obtained kinetic models will be used to describe the effects of processes parameters on the spherical porous structure. . Based on the above researches, the quantitative relation between the preparation processes, spherical porous structure and electrochemical performance of the prepared MnO/C will be constructed. This quantitative relation can be used to develop the method to design and control the spherical porous structure to obtain the desired electrochemical performance of MnO/C by changing the processes parameters, which make the leap from the micro-and nano-level to the process level. . The results of this proposal not only will help solve the critical problem of this technology and promote its practical application, but also help to further improve the synthetic theory of the porous structured materials in microreactor. This proposal can also provide new ideas for the preparation of materials for lithium ion batteries and the efficient use of manganese resources in Guangxi.

T型微反应器共沉淀法是一种高效制备性能优良多孔MnO/C微球负极材料的新方法，关键是控制材料的球形多孔结构。本项目通过研究多孔MnO/C微球的形成过程，阐明T型微反应器的微观混合特性调控前驱体球形多孔结构的机制，揭示热处理过程中前驱体转化为多孔MnO/C微球的机制，获得前驱体的成核生长模型和热处理过程的多相反应动力学方程。借鉴传统多相反应建立动力学模型的思路，建立球形多孔结构形成过程的数学模型，定量描述制备工艺对其形成过程的影响。在此基础上，建立T型微反应器共沉淀法制备多孔MnO/C微球的工艺、球形多孔结构和电化学性能之间的定量关系，提出在可操作的宏观工艺尺度设计和控制材料的球形多孔结构和电化学性能的方法。研究结果不仅可为该方法制备多孔MnO/C微球提供理论指导，促进其实际应用；而且也有助于进一步完善微反应器中多孔材料的合成理论，并为锂离子电池材料的制备和广西锰资源的有效利用提供新的思路。

导电性差是影响MnO性能的主要原因。本项目主要研究T型微通道反应器（TMR）制备多孔MnO/C提高电化学性能，并研究了制备工艺、性能和机理。. 硫酸锰与碳酸氢铵和草酸铵在TMR中反应生成碳酸锰微球和中空草酸锰微管，与碳源混合-热解得循环和倍率性能优良的多孔MnO/C微球(1C, 655 mAh·g–1)和中空多孔MnO/C微管(5C, 699 mAh·g-1)，主要是介孔多孔微球和多孔中空微管结构提高了结构稳定性和导电性。. TMR制备碳酸锰和中空草酸锰的平均停留时间分别为3.4和4.2ms，远小于传统共沉淀法的平均停留时间，可在极短时间内完成沉淀反应。碳酸锰和草酸锰沉淀过程的微观混合特征时间为 0.578和 0.413ms，小于成核诱导特征时间(~1 ms)，说明 TMR中过饱和度能通过微观混合在成核前达到均匀分布，为结晶提供均匀的反应环境，获得均匀的碳酸锰立方体和球形草酸锰。. TMR中颗粒-流体作用力主要取决于流体速度，其切向分力能从团聚体剥落一次粒子，径向分力可沿径向压缩团聚体，对颗粒形貌有关重要的影响。在混合室中产生的草酸锰粒子在颗粒间作用力的作用下倾向于形成一维团聚体。TMR中高速流体流过一维草酸锰团聚体的内部空隙时，产生很强的流体-颗粒相互作用力，其切向分力能从团聚体中剥离一次粒子，直到与颗粒间力作用力平衡为止，法向分力沿径向压缩团聚体，在团聚体内部形成沿流动方向的流体通道，形成中空管状结构。碳酸锰立方体在流体-颗粒作用力的作用下在随机旋转运动中与其它粒子团聚，并在径向分力压缩下形成球形团聚体。. 掺杂离子种类和用量能调控草酸锰和Mn1-xMxO的形貌，且SEI 膜扩散活化能、转换反应表观活化能及锂离子扩散活化能随掺杂量的增加先减小后增大。Mn0.95Mg0.05O、 Mn0.9Cu0.1O和Mn0.85Zn0.15O的10C容量比MnO提高250、170和140 mAh·g-1，具有较好的循环和倍率性能，主要是金属离子进入 MnO 晶格形成固溶体，改变原子核外电子分布，提高材料导电性能，放电中形成的惰性组分可限制活性粒子团聚长大。. 本项目有关T 型微通道反应器中高速流体-颗粒相互作用力和掺杂离子调控材料微观形态方面的研究为调控电极材料形貌提供了一条新途径。..