Stress and Deformation caused by Insertion in Li Ion Batteries

锂离子电池是各种应用的首选电池，特别是对尺寸和重量敏感的应用，如便携式电子产品和电动汽车。锂离子电池的核心是一个将电化学和力学结合在一起的挑战性问题。锂离子电池中的每个电极都是锂的宿主，在电池充电和放电时吸收或渗出锂。反复的锂化和脱硫化会导致循环变形和可能的破裂，这是一种已知的导致电池容量衰退的机制。锂离子引起的变形和断裂是制约高容量电池发展的瓶颈。本项目将发展理论并进行实验，以研究各向异性插入、颗粒大小和变化率的影响。此外，该项目将建立一个非弹性主体中质量传输和变形耦合的理论，并使用该理论来研究应力、锂浓度和表面形态的共同演化，这是最近文献中报道的现象。考虑到电池对正在经历环境和资源态度深刻转变的社会的作用，机械和电化学的结合是及时的。PI已经开始将电化学整合到一门力学课程中，并在网上发布了课程材料。这个项目的教育影响已经从PIs小组中研究生的热情中可见一斑。他们的想象力被这个独特的机会所激发，将力学学科带入将改变社会的技术的核心。

Lithium-ion batteries are the batteries of choice for diverse applications, especially for those sensitive to size and weight, such as portable electronics and electric cars. At the heart of a Lithium-ion battery is a challenging problem that couples electrochemistry and mechanics. Each electrode in a Lithium-ion battery is a host for Lithium, absorbing or exuding Lithium when the battery is charged and discharged. Repeated lithiation and delithiation induce cyclic deformation and possibly fracture, a mechanism known to cause the capacity of the battery to fade. Lithiation-induced deformation and fracture is a bottleneck in developing batteries of high capacity. This project will develop theory and conduct experiments to study effects of anisotropic insertion, particle size and changing rate. Furthermore, the project will formulate a theory of coupled mass transport and deformation in inelastic hosts, and use the theory to study co-evolution of stress, Lithium concentration, and surface morphology, a phenomenon reported in recent literature. Given the role of batteries to the society undergoing a profound transformation in its attitude toward environment and resources, the integration of mechanics and electrochemistry is timely. The PIs have already begun to integrate electrochemistry into a course in mechanics, and posted course materials online. The educational impact of this project is already evident from the enthusiasm of the graduate students in the PIs' groups. Their imagination is captured by this unique opportunity to bring the discipline of mechanics to the heart of a technology that will transform society.