Layered Composites from Branched Nanofibers for Lithium Ion Batteries

大容量、高放电率的电池对许多技术来说都是必不可少的，但它们的使用受到了令人担忧的安全和寿命记录的阻碍。这些问题源于树枝晶的生长，树枝晶刺穿离子传导膜并导致短路，导致容量衰减、过热和火灾。树枝状突起是在电极表面形成的类似蕨叶的微小分枝状金属突起。它们有许多纳米级的尖端，可以对膜施加很大的压力。抑制树枝状生长的尝试取得的成功有限，并突显了一个事实，即安全的高性能电池所需的材料性能从根本上很难获得。这一材料工程问题的解决将使电池性能的显著改善成为可能，而不会牺牲其安全性。该项目将专注于离子导电膜(ICM)的材料工程，旨在使其变得坚固、坚韧，并对高温具有弹性。将采用一种新的方法来构建离子导体和一种新的纳米级组件。新一代ICM将使用逐层组装(LBL)制造，这种组装在复合材料的构建中提供纳米级的精度。密歇根大学最近发现的支化芳纶纳米纤维(ANF)将在薄膜的分层制造过程中用作超强成分。这些膜将由ANF和离子导电聚合物制成，并系统地研究对锂树枝晶的抑制。将准备大容量电荷存储电池的原型，并对其进行性能和安全性测试。

High-capacity, high-discharge rate batteries are essential for many technologies but their use has been hampered by troublesome safety and longevity records. These problems stem from the growth of dendrites that pierce ion conducting membranes and cause short-circuits leading to capacity fade, overheating, and fires. Dendrites are microscale branched metallic protrusions shaped as fern leaves forming on the surface of electrodes. They have numerous sharp nanoscale tips that exert large pressure on the membranes. Attempts to inhibit dendritic growth have met with limited success and highlight the fact that materials properties needed for safe high-performance batteries are fundamentally difficult to obtain. Resolution of this materials engineering problem will make possible a marked improvements in the performance of batteries without sacrificing their safety. This project will be focused on materials engineering of ion-conducting membranes (ICMs) aimed at making them strong, tough, and resilient to high temperatures. A new method will be employed for constructing ion-conductors and a new nanoscale component. The new generation of ICMs will be made using layer-by-layer assembly (LBL) that affords nanoscale precision in construction of composites. Branched aramid nanofibers (ANFs) discovered recently at the University of Michigan will be utilized as the ultrastrong component during the layered manufacturing of the membranes. The membranes will be made from ANF and ion-conducting polymers and systematically investigated for suppression of lithium dendrites. The prototypes of high capacity charge storage cells will be prepared and tested for performance and safety.