绿色高效制备纤维素基聚合物电解质多孔膜及其在锂离子电池中的应用研究

Porous polymer electrolyte membranes are attractive for developing polymer lithium ion battery (PLB) because of the combined advantages of liquid and solid polymer electrolyte. But their preparation process is complex, and usually various solvents are used. What’s more, it is hard to simultaneously obtain the porous polymer electrolyte membranes with high ionic conductivity and mechanical properties. How to address these problems becomes a real challenge for both scientific and industrial fields. . In order to solve the above issues, we will design and synthesize a series of poly(lithium methacrylic acid) (PMALi) and PMALi copolymers with different lithium content, and then blend PMALi/PMALi copolymers with water-soluble cellulose derivatives possessing excellent film-forming ability, good mechanical properties and thermal stability in water. Due to the coordination interaction of Li+ with the oxygen of cellulose derivatives, the blend membranes will present micro-phase separation, which will lead to the formation of porous structure. The interaction between PMALi/PMALi copolymers with cellulose derivatives with different viscosity and degree of substitution will be investigated in detail, in order to find out the relationship between the porous structure and micro-phase separation. Via this investigation, a green and effective fabrication mechanism for porous polymer electrolyte membranes will be proposed for the first time. The porous morphology, the adsorption for liquid electrolyte, ionic conductivity as well as the electrochemical properties for this new porous polymer electrolyte membrane will be systematically studied, and relationship among the structure of porous polymer electrolyte membranes and their properties will be established. Besides this, a novel method for simultaneously obtain the porous polymer electrolyte membranes with high ionic conductivity and mechanical properties will be revealed. Therefore, this project has both scientific meaning and application prospects, which will provide a scientific basis for the actual application of this new porous gel polymer electrolyt in PLB.

针对聚合物电解质多孔膜制备过程繁琐、需要使用多种有机溶剂，以及存在离子电导率与基材机械强度难以同时提高的技术难题，本项目拟通过分子设计合成一系列锂离子含量不同的聚甲基丙烯酸锂及共聚物，然后将其与具有优异成膜性、较好机械强度和热稳定性的水溶性纤维素衍生物在水中进行共混。由于锂离子与纤维素上的氧原子发生配位作用导致微相分离，进而形成多孔结构。详细研究具有不同黏度、取代度及不同化学环境氧原子的纤维素衍生物与聚甲基丙烯酸锂及共聚物的相互作用及相形态演变，弄清微相分离与孔洞形成的关系，提出绿色高效制备多孔聚合物基材的新机制。通过对制备的聚合物电解质多孔膜的形貌、对液体电解质浸取情况、离子电导率及电化学性能的研究，建立多孔凝胶聚合物电解质结构与其性能的构效关系，探索出获得同时具有较高离子电导率和综合性能优异的聚合物电解质多孔膜的新方法，为该多孔凝胶聚合物电解质在聚合物锂离子电池中的应用奠定科学基础。

针对聚合物电解质多孔膜制备过程繁琐、需要使用多种有机溶剂，以及存在离子电导率与基材机械强度难以同时提高的难题，本项目通过设计合成了高锂离子含量的聚甲基丙烯酸锂，利用其与与纤维素的配位作用在水制备出多孔膜，多孔膜的拉伸强度介于16.7-5.8 MPa，电导率达到1.39×10-3 S cm-1，同时在200 °C以下的环境中保持稳定。详细研究了二者的相互作用及微观相分离行为，提出了聚合物多孔膜制备的新机制。在此基础上，为了提高锂离子电池的安全性能，以多孔膜为基材，通过原位聚合、聚合物复合、有机-无机杂化等多种方式将含磷聚合物、聚离子液体、二氧化硅改性聚离子液体等引入其中制备了多种凝胶聚合物电解质，详细研究了电解质的形貌、热性能、机械性能、电化学性能以及安全性能等，制备出了同时具有高安全性和高电化学性能的锂离子电池，构建了结构与性能的关系，为聚合物电解质在高安全性锂离子电池中的应用奠定了科学基础。在本项目的资助下，已发表SCI论文11篇，影响因子在6.0以上的8篇，申请发明专利1项，培养研究生6人（2人在读），完全达到预期设计，实现了项目的研究目标。