金属锂负极表面有序结构对锂离子电沉积溶解行为的影响

发布时间：2018-03-12 08:11

本文选题：金属锂电池　切入点：锂负极　出处：《中国科学院大学(中国科学院物理研究所)》2017年硕士论文　论文类型：学位论文

【摘要】：金属锂由于其极高的理论容量(ca.3860mAh/g,2060mAh/cm3)和极低的电极电势(-3.045V相对于标准氢电极)而被用于锂电池中。不可控的锂枝晶生长,无限的体积膨胀和低的循环效率困扰了研究者们多年。最近由于Linda Nazar和Peter G.Bruce对Li-S,Li-O2电池的研究以及固态电解质的最新进展使得金属锂重新被重视。金属锂的改性有多种方法,如:在电解液中添加添加剂,3D集流体做骨架支撑,固态电解质的机械压制,金属锂的表面处理,使用锂金属合金,采用高盐浓度电解液,目的是为了解决金属锂存在的问题,目前还没有找到合适的方法。我们研究了孤立导体表面静电平衡下的电场分布对锂离子在液态电解液中沉积溶解动力学行为的影响,通过在金属锂表面制备大面积有序的结构的方法对金属锂作改性处理,并用微加工的方法首次成功地在金属锂表面大面积地制备了具有六角密排的亚微米圆柱形孔洞结构,分为500nm,5um,50um三种孔径。使用具有该结构(pattern)的锂负极装配了CR2032扣式电池和三电极电池电池,采用不同体系电解液进行电化学测试,将测试后的电池拆解出锂负极清洗后采用SEM进行形貌的观察。锂离子在金属锂表面的沉积和溶解受到微观电场的调控,部分锂离子在pattern的孔洞侧沿电场最强处以金属锂的形式均匀沉积。此外,微观结构使电极的比表面积增大,使电极表面真实电流密度降低。一方面增大了锂枝晶的形成时间τ,抑制锂枝晶的生成,另一方面降低了电极的极化。采用三电极电池壳分析了锂离子进入孔洞的量,对三电极电池做一周沉积后,在扫描电镜下找出其中多个任意区域做大数据统计可以得到锂离子在孔洞内沉积的半定量结果。
[Abstract]:Lithium metal has been used in lithium batteries because of its extremely high theoretical capacity (Ca. 3860 mAh/ g) and extremely low electrode potential (-3.045V relative to the standard hydrogen electrode). The infinite volume expansion and low cycle efficiency have puzzled researchers for many years. Recently, due to the research of Li-Su Li-O2 batteries by Linda Nazar and Peter G. Bruce and the recent development of solid electrolyte, lithium metal has been revalued. There are many ways to modify lithium metal. For example, adding additives such as 3D fluid collection to electrolyte as skeleton support, mechanical compaction of solid electrolyte, surface treatment of lithium metal, use of lithium metal alloy, use of electrolyte with high concentration of salt to solve the problem of metal lithium, At present, no suitable method has been found. We have studied the effect of electric field distribution on the deposition and dissolution kinetics of lithium ions in liquid electrolyte under electrostatic equilibrium on the surface of isolated conductors. Lithium metal was modified by preparing large area ordered structure on the surface of lithium metal. For the first time, the submicron cylindrical structure with hexagonal compact arrangement was successfully fabricated on the surface of lithium metal by micromachining. The lithium anode with this structure is used to assemble the CR2032 button battery and the three-electrode battery, and the electrochemical tests are carried out using different electrolyte solutions. The morphology of lithium anode was observed by SEM after the battery was disassembled out of the tested battery. The deposition and dissolution of lithium ion on the surface of lithium metal were controlled by microelectric field. Some lithium ions are deposited uniformly in the form of lithium in the form of metal lithium along the hole side of pattern, and the microstructure increases the specific surface area of the electrode. The real current density on the electrode surface is decreased. On the one hand, the formation time of lithium dendrite is increased, and the formation of lithium dendrite is inhibited, on the other hand, the polarization of the electrode is reduced. After one week deposition of the three-electrode battery, the semi-quantitative results of lithium ion deposition in the pore can be obtained by using big data statistics in several arbitrary areas under scanning electron microscope.
【学位授予单位】：中国科学院大学(中国科学院物理研究所)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.26;TM912

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