溶胶-喷雾干燥制备锂离子电池纳/微结构LiMnPO4/C正极材料

Nano/micro-structured electrode materials combine the advantages of nano-materials and micro-materials. The biggest hurdles for nano/micro-structured electrode materials to succeed in commercial ltihium ion batteries are the relatively complex synthesis processes and the associated costs. Sol-spray drying is an effective way to prepare nano/micro-structured materials, which was used to prepare nano/micro-structured LiMnPO4/C with good electrochemical performance. And the ability to control the nano/micro-structure formation to obtain the desired electrochemical properties is the key for this method to success. This proposal will focus on investigating the critical problem of controlling the nano/micro-structure formation and solve it. First, the principles and methodologies of heterogeneous reaction kinetics will be used to investigate the effects of the reaction and transport performance of the preparation processes on the formation of nano/micro structured LiMnPO4/C. These results will be used to identify the formation mechanism of nano/micro structure LiMnPO4/C, and determine its formation kinetic equations. Second, the principles and methodologies of electrochemical reaction engineering will be applied to investigate the effects of the nano/micro structure on the reaction and transport performance of electronic and Li+ in the charging and discharging process, and the obtained results will be used to clarify the mechanism for the nano/micro-structure of LiMnPO4/C to determine its charging/discharging process and electrochemical properties. Based on the above researches, the quantitative relation between the preparation processes, nano/micro-structure and electrochemical performance of LiMnPO4/C will be constructed. This quantitative relation can be used to develop the method to design and control the nano/micro structure to obtain the desired electrochemical performance of LiMnPO4/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 nano/micro structured LiMnPO4/C and promote its practical application, but also help to further improve the synthetic theory of the nano/micro structured materials.

纳/微结构电极材料综合了纳米和微米电极材料的优点，其应用的最大障碍是合成工艺复杂、成本高。溶胶-喷雾干燥能廉价、高效地制备性能优良的纳/微结构LiMnPO4/C正极材料，关键是如何控制材料的纳/微结构。本项目采用多相反应动力学的原理和方法研究制备过程的反应-传递性能对纳/微结构LiMnPO4/C形成过程的影响，阐明纳/微结构的形成机制，确定纳/微结构LiMnPO4/C形成过程的动力学方程。采用电化学反应工程的原理和方法研究纳/微结构对充放电过程中Li+和电子反应-传递性能的影响，阐明纳/微结构影响充放电过程和电化学性能的机制。建立纳/微结构LiMnPO4/C的制备过程与纳/微结构和电化学性能的定量关系，获得在宏观工艺尺度设计和控制材料纳/微结构和电化学性能的方法。本项目的完成不仅可解决纳/微结构LiMnPO4/C制备中的难题，促进其实际应用，而且也有助于进一步完善纳/微结构材料的合成理论。

与LiFePO4相比，LiMnPO4拥有更高的电压平台和更大的能量密度，然而较差的电化学性能限制了它的实际应用。纳/微结构LiMnPO4综合了纳米和微米材料的优点，但合成工艺复杂、成本高。本项目采用廉价、高效的溶胶-喷雾干燥方法制备纳/微结构LiMnPO4/C，重点研究了材料纳/微结构的形成与控制。. 前驱体LiMnPO4的合成研究表明表面活性剂和溶剂的模板效应可诱导晶体的生长，微波效应以缩短高温反应时间。水/二甘醇混合溶剂生成片状LiMnPO4。不添加表面活性剂合成的是纺锤形粒子，加入CTAB则得细小梭状颗粒团聚体，PVPk30制备的是片状粒子，PVPk90得到的是棒状和纺锤状团聚体。氯化胆碱/乙二醇低共熔溶剂中传统加热法得到LiMnPO4/纳米棒，微波加热则是纳米纺锤体。 . 湿法球磨制备溶胶的一次粒径随着球磨中的球磨转速、循环流速和固含量的增加而先减小后增大，随蔗糖用量和球磨时间的增加而减小，直至基本保持不变。桨料经喷雾干燥-固相反应可得到2-15μm的多孔中空LiMn0.85Fe0.15PO4/C微球， 1C放电比容量为135mAh/g，循环50圈无衰减，表现出了良好的电化学性能。. 氯化胆碱-乙二醇合成的纳米纺锤体LiMnPO4溶胶经喷雾干燥后得到多孔球形颗粒，但在较低的浆料浓度、进风温度、进料速率、焙烧温度、蔗糖用量下二次颗粒的球形度变差。材料的放电比容量随着浆料浓度、进风温度、进料速率、焙烧温度、焙烧时间的升高而先增大后减小，随着蔗糖用量的增大而逐渐减小，但循环性能却逐渐变好。所得微球的1 C放电比容量为140 mAh·g-1，100次循环后容量保有率为95%，5 C放电比容量为119 mAh·g-1，表现出了良好的循环性能和倍率性能。多孔微球电极过程动力学结果说明SEI膜扩散活化能随浆料浓度和焙烧温度的增大先减小后增大，体相扩散活化能随着焙烧温度的升高先减小后增大，而浆料浓度对反应活化能和体相扩散活化能的影响较小。. 本项目有关溶胶-喷雾干燥制备纳/微结构LiMnPO4/C工艺和机理的研究，不仅为制备纳/微结构电极提供了一种简便的方法，可解决纳/微结构电极材料制备中的难题，促进其实际应用，而且进一步完善纳/微结构材料的合成理论。