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.
