Extensional rheology of battery electrode slurries with water-based binders

Abstract

Precise rheological properties of inks and slurries are essential to providing homogeneous, well controlled and reproducible coatings, particularly in electrode manufacturing for batteries. The rheology can aid understanding of the slurry structure, as well as optimisation of the process conditions to create electrode coatings with the desired microstructure. The shear rheology is typically measured, however the mixing and coating steps contain significant extensional flows, this omits a significant part of the rheological response. Here the extensional properties of battery electrode slurries are quantified using a miniature extensional rheometer. This requires tiny samples (<1 ml) and provides rapid capture of the extensional properties, allowing easy repetition. The extensional behaviour varies significantly between different formulations and binder systems. The additional extensional rheometry measurements are key for understanding flow in a coater and the underlying slurry structure, and are not predicted by shear rheology. This novel extensional rheology technique, applied to battery electrode slurries, provides key rheological parameters, rapidly, and is essential to understanding the precise rheological properties and control for coating depositions.

Keywords

• Extensional rheology
• Electrode slurry
• Battery manufacturing
• Sustainable binders
• Metrology