Visualization of styrene-butadiene rubber (SBR) latex and large-scale analysis of the microstructure of lithium-ion battery (LIB) anodes

This study presents a novel method for analyzing binder distribution in a lithium-ion battery (LIB) anode. The developed method is based on scanning electron microscope (SEM) image analysis and can be used to analyze an aqueous styrene-butadiene rubber/carboxymethylated cellulose (SBR/CMC) binder system. The main advantage of this method is that it can provide large-scale cross-sections of multiple samples in a single milling process while maintaining a high-quality cross-section enabling the clear distinction of electrode components. This minimizes the issue of SEM-based analysis in the selection of a representative analysis area. The sample preparation and image acquisition processes were optimized to obtain high-quality images, and image processing procedures were developed for quantitative analysis. Osmium tetroxide (OsO4) staining and resin embedding enabled us to achieve a smooth two-dimensional (2D) cross-section with a clear distinction of the electrode components. The milling process enabled us to produce high-quality large-scale cross-sections similar to those prepared by ion beam milling methods. It was verified that our developed method is reliable in determining the SBR content and porosity. The developed method was used to analyze the SBR distribution and pore structure of anode layers prepared at various drying temperatures.