锂离子电池用PVDF-HFP基纳米复合聚合物电解质的研究

发布时间：2018-06-22 18:53

本文选题：偏二氟乙烯-六氟丙烯共聚物 + 纳米二氧化钛　；参考：《中南大学》2014年博士论文

【摘要】：摘要：与商品化的液态锂离子电池相比,聚合物锂离子电池具备较高的安全性、优越的外形设计灵活性以及更高的质量比能量,成为新一代锂离子二次电池研究的热点。开发性能优越的聚合物电解质作为制备高性能聚合物锂离子二次电池的有效途径,已受到广泛关注,其中,纳米复合聚合物电解质膜的研究成为开发高性能聚合物电解质重要方向之一。然而,由于纳米无机颗粒极易团聚,很难分散在聚合物电解质基体,团聚的纳米粒子丧失了纳米材料本身所具备的特性,其增强的聚合物电解质膜性能受到限制。因此,本论文从根据分散的一般策略,从抑制纳米颗粒团聚的角度设计合成可用来增强PVDF-HFP凝胶型聚合物电解质膜性能的纳米Ti02有机-无机复合体,并对纳米复合体合成制备工艺、聚合物复合电解质膜的结构与性能以及纳米粒子增强聚合物电解质膜电导机理展开了研究,并取得以下研究成果： 1)为了克服纳米Ti02颗粒之间的团聚问题,利用原位聚合与结晶的方法成功合成了高分散的纳米TiO2-PMMA复合体,纳米TiO2颗粒表面通过偶联剂乙烯基三乙氧基硅烷“键桥作用”,接枝了PMMA分子层,抑制了纳米Ti02团聚。 2)以聚烯烃隔膜为支撑层,将原位合成的高分散纳米TiO2-PMMA复合体与PVDF-HFP复合,制备出以聚烯烃隔膜为支撑层的夹层复合聚合物电解质膜,并利用扫描电镜、线性扫描伏安法、交流阻抗测试、充放电电池测试等表征手段对复合电解质膜的结构与性能进行了研究。结果表明,在PVDF-HFP中添加高分散的纳米TiO2-PMMA复合体,可显著改善了PVDF-HFP聚合物电解质膜的电池性能,特别是倍率性能。提高纳米TiO：颗粒在PVDF-HFP聚合物复合电解质膜中的分散性,可有效提高复合电解质膜的离子电导率、电极相容性,从而起到增强聚合物复合电解质膜的电池性能的效果,其中,电极相容性的改善是聚合物电池倍率性能得到提高的主要原因。 3)原位聚合与结晶的方法成功合成了单分散的纳米TiO2@Li+单离子导体(TiO2-PAALi-PMMA),利用合成过程的酸碱反应,降低了纳米Ti02分散能耗,有效提高了纳米Ti02分散效率,得到单分散的单离子导体DMF分散液。 4)以PVDF-HFP静电纺丝膜为支撑层,利用相分离法制备了单离子导体TiO2@Li+/PVDF-HFP复合电解质膜,膜的厚度控制在45μm左右,复合电解质膜具备较好的机械强度、抗热收缩性能、电化学性能以及电池性能。其中,当复合层纳米单离子导体含量为50wt%时,复合膜的断裂强度达到39MPa,活化后的电解质膜离子电导率达到3.63×10-S cm-1,离子迁移数为0.52,倍率性能和循环性能相对于PE隔膜电池均得到改善。 5)单分散的纳米TiO2@Li+单离子导体分散在PVDF-HFP聚合物电解质膜中存在“自组装”行为。复合电解质膜内部的纳米单离子导体向膜与电极接触的界面以及基体内膜孔内表面离析与富集,富集在电解质与电极界面的纳米粒子增强了电极与电解质的界面相容性,降低了界面电阻。富集在复合膜内孔隙的纳米粒子因双电层效应产生“快离子传导通道”,从而起到提高聚合物复合电解质膜离子电导率的效果。
[Abstract]:Abstract: compared with the commercialized liquid lithium ion battery, the polymer lithium ion battery has high safety, superior shape design flexibility and higher mass ratio of energy. It has become a hot spot in the research of the new generation of lithium ion two battery. The development of high performance polymer electrosolution is used as the preparation of high performance polymer lithium ion two times The effective ways of the battery have attracted much attention. Among them, the research of nanocomposite polymer electrolyte membrane has become one of the important directions for the development of high performance polymer electrolytes. However, it is difficult to disperse on the matrix of polymer electrolyte because of the easy aggregation of nano inorganic particles. The aggregation nanoparticles lose the special properties of nanomaterials themselves. The performance of the enhanced polymer electrolyte membrane is limited. Therefore, in this paper, the nano Ti02 organic-inorganic complex, which can be used to enhance the properties of the PVDF-HFP gel polymer electrolyte membrane, is designed and synthesized from the point of view of dispersing the agglomeration of nanoparticles. The structure and properties of electrolyte membrane and the conductivity mechanism of nanoparticle reinforced polymer electrolyte membrane have been studied.
1) in order to overcome the agglomeration of nano Ti02 particles, the highly dispersed nano TiO2-PMMA complex was successfully synthesized by in-situ polymerization and crystallization. The nano TiO2 particles were grafted by the coupling agent vinyl triethoxy silane "bond bridge", and the PMMA molecular layer was grafted to inhibit the nano Ti02 agglomeration.
2) the composite polymer electrolyte membrane with polyolefin membrane as the supporting layer was prepared by using polyolefin diaphragm as the supporting layer, and the polyolefin membrane as the supporting layer was prepared. The composite electrolyte membrane was characterized by scanning electron microscopy, linear scanning voltammetry, AC impedance testing, charge discharge battery test and other characterization means. The results show that the addition of highly dispersed nano TiO2-PMMA complexes in PVDF-HFP can significantly improve the battery performance of the PVDF-HFP polymer electrolyte membrane, especially the ratio performance. The enhancement of nano TiO: the dispersion of particles in the PVDF-HFP polymer electrolyte membrane can effectively improve the composite electrolyte. The ionic conductivity and electrode compatibility of the membrane can enhance the battery performance of the polymer composite electrolyte membrane, in which the improvement of the compatibility of the electrode is the main reason for the increase of the performance of the polymer battery.
3) the single dispersed nano TiO2@Li+ single ion conductor (TiO2-PAALi-PMMA) was successfully synthesized by in-situ polymerization and crystallization. Using the acid base reaction of the synthesis process, the energy consumption of nano Ti02 was reduced, and the dispersion efficiency of nano Ti02 was improved effectively, and monoionic monomer DMF dispersion was obtained.
4) the single ionic conductor TiO2@Li+/PVDF-HFP composite electrolyte membrane was prepared by phase separation method with the PVDF-HFP electrospun membrane as the supporting layer. The thickness of the membrane was controlled at about 45 m. The composite electrolyte membrane had good mechanical strength, thermal shrinkage resistance, electrochemical performance and electric pool performance. At 50wt%, the fracture strength of the composite membrane reaches 39MPa. The ionic conductivity of the electrolyte membrane after activation reaches 3.63 x 10-S cm-1 and the ion migration number is 0.52. The ratio and cycling performance of the membrane are improved compared with the PE membrane battery.
5) the single dispersed nano TiO2@Li+ single ion conductor is self assembled in the PVDF-HFP polymer electrolyte membrane. The interface of the nano single ion conductor to the membrane and the electrode in the composite electrolyte membrane, and the surface segregation and enrichment of the inner surface of the matrix, the nanoparticles enriched in the electrolyte and the electrode interface enhanced the electrode The interfacial compatibility with the electrolyte reduces the interfacial resistance. The nanoparticles enriched in the pores in the composite film produce the "fast ion conduction channel" due to the double layer effect, thus improving the ionic conductivity of the polymer composite electrolyte membrane.
【学位授予单位】：中南大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM912

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