Microstructural evolution of graphite electrode during calendering using 3D reconstruction technique

Abstract

Calendaring is considered a predominant process in Li-ion battery (LIB) production which heavily influences the microstructure of the electrode, thus affecting the overall performance of the battery. Therefore, careful investigation of the calendaring impact on electrode microstructure is necessary to optimize the design of LIB. This work introduces the method to simulate the microstructure evolution of an electrode upon calendaring stress based on an experimentally constructed three-dimensional (3D) model. As a result, variations of microstructural and transport properties such as porosity, pore size distribution, tortuosity, and specific active surface area of the electrodes were observed under incremental calendering strains. The simulated structure had structural and transport properties similar to those of the real calendared electrode microstructure when compressed to the same degree. The result also suggested that applying calendaring strain over 30% could be detrimental to the electrode performance as it can greatly increase closed porosity and pore tortuosity as well as reduce the specific active surface area of the electrode. Through this study, microstructural evolution and property changes with varying compression degrees could be analyzed visually as well as quantitatively. This can provide insights into determining the calendering limit that secures maximum electrode performance from its microstructure.