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，特别是对于那些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具有挑战性的问题，它将电化学和力学结合在一起。 锂离子电池中的每个电极都是锂的宿主，当电池充电和放电时吸收或释放锂。 重复的锂化和脱锂会引起循环变形和可能的断裂，这是一种已知的导致电池容量衰减的机制。 锂化引起的变形和断裂是发展高容量电池的瓶颈。 本计画将发展理论并进行实验，以研究各向异性插入、粒径及变化率的影响。 此外，该项目将制定非弹性宿主中耦合质量传输和变形的理论，并使用该理论研究应力，锂浓度和表面形态的共同演变，这是最近文献报道的现象。 考虑到电池对社会的作用，社会对环境和资源的态度正在发生深刻的转变，机械和电化学的整合是及时的。PI已经开始将电化学纳入力学课程，并在网上发布课程材料。 这个项目的教育影响已经从研究生在PI组的热情中显而易见。 他们的想象力被这个独特的机会所吸引，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.