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，但它们的使用一直受到安全性和寿命记录问题的阻碍。这些问题源于树突的生长，这些树突会刺穿离子导电膜，导致短路，导致容量衰减、过热和火灾。树突是在电极表面形成的类似蕨类植物叶子的微尺度分支金属突起。它们有许多锋利的纳米级尖端，可以对膜施加很大的压力。抑制枝晶生长的尝试取得了有限的成功，并突出了一个事实，即安全高性能电池所需的材料特性从根本上难以获得。这一材料工程问题的解决将使电池在不牺牲其安全性的情况下显著提高性能成为可能。本项目将专注于离子导电膜（ICMs）的材料工程，旨在使其坚固、坚韧、耐高温。将采用一种新的方法来构建离子导体和新的纳米级元件。新一代ICMs将采用逐层组装（LBL）制造，从而在复合材料的构建中提供纳米级精度。最近在密歇根大学发现的支链芳纶纳米纤维（ANFs）将被用作薄膜分层制造过程中的超强成分。该膜将由ANF和离子导电聚合物制成，并系统地研究对锂枝晶的抑制作用。将制备高容量充电电池的原型，并对其性能和安全性进行测试。

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.