基于电纺纳米纤维的锂电隔膜研究

发布时间：2018-05-20 14:17

  本文选题：锂离子电池 + 隔膜　； 参考：《厦门大学》2014年硕士论文

【摘要】：隔膜置于锂离子电池正负极之间,即可防止正负电极直接物理接触,也为锂离子提供正负电极间的传输通道。它的结构严重影响电池界面结构和内阻等。电纺纳米纤维膜以其高孔隙率特质在锂离子电池应用中大大提高电池性能,未来将成为隔膜的主要形式之一,但其力学强度和安全性方而依旧存在不足,论文主要围绕这两个方面分别展开研究。 论文先以聚偏氟乙烯(PVDF)纳米纤维膜为研究对象,研究了PVDF纳米纤维膜的主要电纺工艺参数对纳米纤维直径及形貌的影响,包括溶剂比、溶液浓度、偏置电压、工作距离和供给速率。研究结果表明,溶剂DMF和工作距离的增加使得纳米纤维直径变小,而浓度、电压以及供液速率的增加则导致纤维直径变粗。PVDF纳米纤维膜具有高孔隙率、吸液率以及离子电导率等特性使得其放电比容量衰减小。经100循环后,PVDF隔膜电池的放电比容量衰减仅为8.2%。 研究提高PVDF纳米纤维膜力学性能的两种方法。通过热处理使得PVDF内米纤维间相互粘结,在不损坏电纺膜基本结构的前提下将PVDF纳米纤维膜的最大拉伸强度提高了25倍左右,由0.68MPa强化至17.43MPa。采用PET/PVDF复合膜也可提升强度,且具有较高力学性能,最高力学拉伸强度达到34.85MPa。 论文提出采用PI/PVDF/PI(聚酰亚胺)三明治结构纳米纤维膜作为可实现自闭功能的高安全性隔膜。研究结果显示,电纺纳米纤维膜180℃下热缩率小于3%,表现出高热稳定性以及低热缩率。将其应用于锂离子电池,经100循环后,电池依旧保持初始放电容量的97.1%。同时中间PVDF纳米纤维膜在高温下能有效切断电池大部分电流,提高电池安全性。
[Abstract]:If the diaphragm is placed between the positive and negative electrodes of the lithium ion battery, it can prevent the direct physical contact between the positive and negative electrodes, and also provide the transfer channel between the positive and negative electrodes for the lithium ion. Its structure seriously affects battery interface structure and internal resistance. Electrospun nanofiber membrane, with its high porosity, greatly improves the performance of the battery in the application of lithium ion battery, and will become one of the main forms of diaphragm in the future, but its mechanical strength and safety are still insufficient. The thesis mainly focuses on these two aspects. In this paper, the influence of main electrospinning process parameters on the diameter and morphology of PVDF nanofibers was studied, including solvent ratio, solution concentration and bias voltage. Working distance and supply rate. The results show that the diameter of nanofibers decreases with the increase of solvent DMF and working distance, while the increase of concentration, voltage and liquid supply rate leads to the thickening of fiber diameters. The specific discharge capacity attenuation is small due to the characteristics of liquid absorption rate and ionic conductivity. After 100 cycles, the specific discharge capacity of PVDF membrane cell is only 8.2. Two methods to improve the mechanical properties of PVDF nanofibers were studied. The maximum tensile strength of PVDF nanofiber film was increased by about 25 times without damaging the basic structure of electrospun film, which was strengthened from 0.68MPa to 17.43 MPA by heat treatment. The PET/PVDF composite film can also enhance the strength and has higher mechanical properties. The highest tensile strength of the composite film is 34.85 MPA. In this paper, Pi / PVDF / Pi (polyimide) sandwich nanofiber membrane is proposed as a high security diaphragm for self-closing function. The results show that the thermal shrinkage of electrospun nanofiber films is less than 3 at 180 鈩，

本文编号：1914951