Composition analysis of Li/Si Ratio and Silicate in Silicon Based Anodes

Introduction

Synchrotron radiation XAFS is generally used in chemical state analysis for metal elements. However, similar assessments can be performed with X-ray emission spectrometers (XES) as well. XES analysis for Si can also be applied to electrode reaction analysis and degradation analysis.

Chemical state analysis

• Analysis: Anode material
• Analysis method: Linear Combination Fitting
• Use: Improving battery lifetime  
• Analyzed materials: Si metal anodes, SiO anodes

This figure illustrates an XES spectrum for Si Kβ upon initial charging/discharging for SiO-C composite anodes.

Linear combination fitting (LCF) was conducted using a standard spectrum for crystal Si (c-Si), amorphous Si (a-Si), Li₃.₇₅Si (Li-Si), SiO and Li₄SiO₄.

Results

When uncharged, SiO is comprised of a-Si and SiO₂. However, it was ascertained that with charging, Li-Si and Li₄SiO₄ are generated, and that a-Si and Li₄SiO₄ are generated after the cycle. As this shows, state analysis for compounds is also possible using the XES method with laboratory instruments.