In-Situ Experiment and Modeling of Electrode Failures in Li Ion Nano-batteries

这项资助的研究目的是阐明锂离子电池硅纳米线电极电化学驱动机械故障的机制。为了研究单纳米线电极的失效，将对纳米电池进行原位实验和建模。本研究涉及三个紧密耦合的推力：(i)采用纳米力学测试装置定量测量锂化硅纳米线的力学性能。（ii）原位电镜成像将揭示电化学反应引起的变形、非晶化和开裂的实时过程。（iii）原子和有限元建模将使我们能够理解在时间和尺寸尺度上具有原子尺度保真度的电池实验的应力产生、裂纹萌生和扩展。先进的电池技术对于从便携式电子产品到电动汽车的应用至关重要。锂离子电池是目前性能最好的电池，但其容量和可靠性有限。由于硅具有最高的理论充电容量，因此被认为是锂离子电池极具前景的电极。然而，硅电极经常遭受机械退化，导致容量衰退。目前，人们对锂化硅的应力产生和破坏机制缺乏了解。该项目将展示和解释裂纹在何时、何地以及如何在锂化硅纳米线中开始和扩展。结果将提供传统电池测试无法提供的电极失效的见解。这项研究将为理解、控制和减轻高容量锂离子电池的材料降解提供基础。

The research objective of this grant is to elucidate the mechanisms of electrochemically driven mechanical failures in silicon nanowire electrodes for Lithium ion batteries. In-situ experiments and modeling of nanoscale batteries will be performed to investigate the failures in single nanowire electrodes. The proposed research involves three tightly coupled thrusts: (i) A nanomechanical testing device will be used to quantitatively measure the mechanical properties of lithiated silicon nanowires. (ii) The in-situ electron microscopy imaging will reveal the real-time processes of electrochemical reaction induced deformation, amorphization, and cracking. (iii) Atomistic and finite element modeling will enable the understanding of stress generation, crack initiation and growth on the time and size scales of battery experiments with atomic scale fidelity. Advanced battery technologies are critically important for applications from portable electronics to electric vehicles. Lithium ion batteries are presently the best performing ones, but they are limited in capacity and reliability. Silicon is being considered as a promising electrode for Lithium ion batteries, due to its highest theoretical charge capacity. However, Silicon electrodes often suffer from mechanical degradation, leading to capacity fading. Currently, there is a lack of understanding of the stress generation and failure mechanisms in lithiated Silicon. This project will show and explain when, where, and how the crack initiates and propagates in lithiated silicon nanowires. Results will provide insights into electrode failures that cannot be offered by traditional battery testing. This research will provide the basis for understanding, controlling, and mitigating materials degradation in high capacity Lithium ion batteries.