高压锂离子电池凝胶聚合物电解质的构建及物理化学性质研究

Developing high voltage cathode is one of the most effective ways to improve the energy density of lithium ion battery. However, the oxidative decomposition potential of the carbonated liquid electrolyte for current lithium ion battery is too low to match high voltage cathode. To solve this problem, we design a new gel polymer electrolyte (GPE) which has high oxidative stability for matching high voltage cathode based lithium ion battery in this project. Firstly, we plan to prepare the active porous nano-skeleton membrane as support, and investigate the relationship between the component of membrane and its properties. Secondly, we will introduce high voltage functional group of monomers such as bi-nitriles and sulfones to form the copolymer by ex-situ and in-situ polymerization. Thirdly, we will select electrolyte additives as interfacial film forming agent to form the electrolyte/electrode interfacial film. Finally, we will prepare GPE based on the developed membrane and the selected electrolyte additive and study its performance in high voltage lithium ion battery. With these experimental investigations, we will explain the mechanism on improved decomposition potential of the electrolyte by introduction of high voltage functional group; the role that the interfacial film plays in compatibility between GPE and high voltage cathode and in process for the extraction/insertion of li-ion; and the contribution mechanism of GPE on the cyclic stability and safety of high voltage lithium ion battery; and obtain the most effective fabrication method of GPE for matching high voltage cathode. The results of this project not only give a new method to solve the problem in using high voltage cathode, but also enrich the physical and chemical theory of electrolyte.

发展高压正极材料是提高锂离子电池能量密度的重要途径，但目前的液态电解质氧化分解电位低，与高压正极材料不匹配。本项目提出凝胶聚合物电解质的解决方案。拟制备活性多孔纳米骨架膜，研究骨架膜组成与性质的关系；分别采用非现场聚合及原位聚合引入耐高压官能团的二腈类或砜类单体形成聚合物，筛选成膜功能分子形成电解质/电极界面膜；制备骨架膜支撑的耐高压凝胶聚合物电解质，组装高压锂离子电池并研究制备凝胶聚合物电解质的实际应用效果。阐明引入耐高压官能团对提高凝胶聚合物电解质氧化分解电位的作用机理；明确界面膜的组分对界面结构与性质及对锂离子脱嵌过程的影响规律；聚合物电解质对提升高压电池的循环稳定性及安全性能的贡献机理。获得匹配高压正极的凝胶聚合物电解质的有效构建方法。研究结果不仅有助于解决高压正极材料的应用问题，而且丰富电解质物理化学的理论内容。

本项目采用凝胶聚合物电解质解决目前液态电解质氧化分解电位低，与高压正极材料不匹配的问题，从设计和应用匹配高压正极材料的电解质的方法来提高锂离子电池能量密度。研究内容及结果如下：（1）不同纳米颗粒掺杂的活性多孔纳米骨架膜的制备及性能表征，阐明了不同纳米颗粒的含量及种类对骨架膜的热稳定性、电化学稳定性及电池循环稳定性的影响；（2）采用乳液聚合等方法合成耐高压的聚丙烯酸酯类凝胶聚合物，采用相转移法、静电纺丝等方法制备对应的聚合物膜，并进行相关物理化学性能研究，明确了不同官能团的含量对提高凝胶聚合物电解质氧化分解电位的贡献机理；（3）将三（三甲基硅烷）硼酸酯（TMSB）等高压界面成膜添加剂添加到液态电解液增塑剂中形成高压凝胶聚合物电解质，研究了凝胶聚合物电解质与高压正极材料（4.4 V钴酸锂、5 V镍锰酸锂）之间的相互作用，从提高正极材料与电解质界面的相容性来提高高压正极材料的循环稳定性及倍率性能，明确了界面膜功能分子对提高界面相容性的作用机理；（4）最后进行高压锂离子电池装配及性能检测，证实了高压电解质的实际应用效果。通过本项目的研究，目前发表SCI论文11篇，其中包括5篇中科院分区为一区的期刊；申请中国发明专利6项，其中1项授权。项目的研究结果不仅有助于解决高压正极材料的应用没有匹配电解质的问题，而且丰富电解质物理化学的理论内容。