CSE 8803 / ME 8883 - Materials Informatics Course - Fall 2016

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20 Aug 2016

Quantitative Analysis of Structural Change in LiCoO2 During Ionic Transport - Blog Post 1 - Background

by Sepideh Parvinian

Background

Electric-field driven transport of ions in the solid state is one of the most studied problems in solid state electrochemistry. This problem has fascinating fundamental statistical physics aspects such as the onset of nonlinear dynamics, as well as crucial technological repercussions such as ion intercalation in Li-ion batteries. The dataset at hand consists of X-ray Diffraction Images that capture in real-time and real-space, the structural changes to an epitaxial crystalline thin-film of (Li Co O2) due to ionic transport induced in it through a local electric field. Quantifying the precise structural changes that result in this thin-film as a function of ionic transport is one of the main objectives. Furthermore, delineating these structural changes from real-time changes in image intensity independent of scattering vector, which indirectly probe the flow of ions is an additional target. Numerous experimental and theoretical studies have been performed on Li Co O2 systems, with the included dataset the first measurement of its kind, therefore this dataset could potentially reveal new aspects of ionic transport and electrochemical strains in the solid state.

Problem Statement

The movement of Li atoms into and out of the electrodes (intercalation of Li ions) is essential for Li- ion batteries performance. Although this transport process has been studied intensively at device level, there is still need to characterize the process at micro/nano scale and to perform quantitative analysis of ion diffusion process which leads to change in lattice structure. (Li diffuses laterally leading to an out-of-plane expansion of the lattice (strain)). These changes in the microstructures can lead to lithium battery aging, degradation and failure.

What we obtain?

• By X-ray Diffraction Intensity Changes due to Li-ion diffusion, the amount of Li-ion diffusing and the shape of the diffusion front can be extracted from this dataset

• Lattice strain

http://imgur.com/ljfUOdo.pnghttp://imgur.com/ljfUOdo.png

Figure 1: Li Co O2 Cathode Structure

Input data

Images of these structural changes were performed with X-ray Diffraction Microscopy (XDM) at Advanced Photon Source, Argonne National Lab

Process – Microstructure Linkage

• Microstructural evolution during Li diffusion as a function of local electric field

• Changes in image contrast (intensity) is due to lattice expansion of Li Co O2

• Different data set that varies as a function of electric field and scattering intensity vector (different processes) (type of diffusion process in microstructures)


http://imgur.com/9UIUDSZ.pnghttp://imgur.com/9UIUDSZ.png

Figure 2: XDM Images as a Function of Electric Field

Please feel free to comment and give your thoughts as we try to update our blog post!

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