Understanding the Failure Mechanisims of Nanoelectrodes in Li-Ion Batteries: Integrating Multiscale Modeling with In-situ Experimental Studies

该奖项的研究目标是通过一种综合的实验/计算方法来阐明硅/碳复合纳米电极中电化学驱动的机械降解机理。纳米电极由沉积在单壁碳纳米管内外表面的硅纳米微滴组成。这项研究有四条紧密结合的线索：i)为Li-Si-C系统开发基于第一原理的反应力场(ReaxFF)，以实现具有量子力学精度的大规模原子模拟；ii)使用ReaxFF进行原子模拟，以提取锂化CNY和硅纳米液滴的基本热力学性质以及锂插入的动力学参数；iii)开发原子信息前沿跟踪有限元方法，以模拟和了解纳米电子中与尺寸相关的形态演变、应力产生和缺陷生长；以及iv)进行电化学驱动变形、缺陷成核、这项研究将有助于对电池电极中发生的复杂、耦合的电化学-机械现象进行尖端的数值模拟和纳米级的现场实验，这些现象会导致电池容量的退化和最终损失。这项研究是高度跨学科的，参与的学生将与桑迪亚国家实验室进行互动和访问；这将使他们接触到尖端的实验设施。

The research objective of this award is to elucidate the mechanisms of electro-chemically driven mechanical degradation in Si/C composite nanoelectrodes through an integrated experimental/computational approach. The nanoelectrodes consist of silicon nanocrystalline droplets deposited on the inner and outer surface of single-walled carbon nanotubes. This research has four tightly-integrated threads: i) develop first-principles based reactive force fields (ReaxFF) for Li-Si-C systems that enable large-scale atomistic simulations with quantum mechanical accuracy, ii) perform atomistic simulations with ReaxFF to extract basic thermodynamic properties of lithiated CNY and silicon nanodroplets as well as the kinetic parameters of lithium insertion, iii) develop an atomistically informed front-tracking finite element method to simulate and understand size-dependent morphological evolution, stress generation, and defect growth in nanoelectodes, and iv) perform in-situ electron microscopy studies of electrochemically driven deformation, defect nucleation, and growth at the nanoscale.This research will contribute both cutting edge numerical simulations and nanoscale in-situ experiments of the complex, coupled electrochemical-mechanical phenomena that occur in battery electrodes and lead to degradation and ultimately loss of battery capacity. The research is highly interdisciplinary and will involve interactions and visits with Sandia National Laboratories for the participating students; this will expose them to cutting-edge experimental facilities.