Theoretical and Experimental Investigations of Coupled Mechanics and Electrochemistry in Silicon Anodes Lithium Ion Batteries

该奖项的研究目标是了解锂离子电池中耦合力学和电化学的基本原理。硅是一种有吸引力的阳极材料，由于其已知的最高理论充电容量为4，200 mAh/g，因此被密切关注用于锂离子电池。然而，硅阳极锂离子电池的发展已经落后，因为它们的大的机械变形，即，在电化学反应期间，高达400%的体积变化，这导致断裂、粉化和早期容量衰减。换句话说，这种耦合机制（例如，体积变化）和电化学问题是硅负极锂离子电池发展的瓶颈。本项目的目的是通过实验和理论相结合的方法来了解锂化硅阳极的基本机械性能。具体的研究将集中在i）纳米压痕实验，以获得锂化对机械性能的影响，作为深度的函数;结合ii）连续介质模型，提取锂化硅阳极在不同荷电状态下的应力-应变曲线。如果成功，本研究的结果将有助于对锂离子电池中硅阳极的耦合力学和电化学的基本理解，特别是锂化硅的机械性能。理论和实验方法也可以应用于锂离子电池中的其他电极和材料，例如阴极。拟议研究的成功实施将有助于材料力学的一个新领域，即耦合力学和电化学，这将可能导致电池和能源相关领域的一系列变革性应用。参与研究的研究生将在多学科环境中接受培训。

The research objective of this award is to understand the fundamentals in coupled mechanics and electrochemistry in lithium (Li)-ion batteries. Silicon is an attractive anode material being closely scrutinized for use in Li-ion batteries because of its highest-known theoretical charge capacity of 4,200 mAh/g. However, the development of silicon anode Li-ion batteries has lagged behind because of their large mechanical deformation, i.e., up to 400 percent volumetric change, during electrochemical reactions, which results in fracture, pulverization and early capacity fading. In other words, this coupled mechanics (e.g., volumetric change) and electrochemistry problem is a bottleneck to the development of silicon anode Li-ion batteries. The objective of this project is to understand the fundamental mechanical properties of the lithiated silicon anodes using combined experimental and theoretical methods. Specific studies will focus on i) nanoindentation experiments to obtain the influence of lithiation on mechanical properties as a function of depth; coupled with ii) continuum modeling to extract the stress-strain curve of lithiated silicon anodes under different state of charges.If successful, the results of this research will help facilitate the fundamental understanding of the coupled mechanics and electrochemistry of silicon anodes in Li-ion batteries, specifically the mechanical behavior of lithiated silicon. The theoretical and experimental methodology can be also applied to other electrodes and materials in Li-ion batteries, such as the cathode. The successful implementation of the proposed research will contribute to a new area of mechanics of materials, namely, coupled mechanics and electrochemistry, which will potentially lead to a range of transformative applications in battery and energy-related fields. The graduate students involved in the research will be trained in a multidisciplinary environment.