Rheological Modeling and Inkjet Printability of Electrode Ink Formulation for Miniature And Interdigital Lithium-Ion Batteries

Habib Temitope-Adebayo Ajose, Wright State University


The rapid advancement of technology has resulted in a greater need for effective energy storage systems to meet the demands of the transportation and electronics industries. Among various energy storage systems, batteries are the most widely used, primarily because of their ability to store significant amounts of energy. In addition, lithium-ion batteries are prevalent for powering portable electronic devices due to their long cycle life, high energy density, and high operating voltage. The traditional doctor-blade approach has been used over the years for producing batteries. Currently, research is being directed to additively manufacture Li-ion batteries via Drop-on-Demand Inkjet Printing with unique architectures towards further increasing energy density and satisfying special applications. The rheology and dispersion of particles in the slurry are critical parameters that affect the performance and printability of batteries in all production routes. In addition, the quality of lithium-ion batteries, including their electrochemical and durability performance, is significantly impacted by the consistency of the slurries used in their production. Thus, a physics-based model that accurately describes the consistency of these slurries is urgently needed to enable the precise optimization of battery manufacturing processes. This work is to develop a computational model to predict the rheology of electrode ink to be printed via Drop-on-demand inkjet printing. The rheology of electrode ink was modeled based on hydrodynamic and colloidal interactions, which include particle interaction, electrostatic forces, steric repulsive forces, and forces due to adsorbed polymer. MATLAB computer routines were used to solve the equations for forces acting in a different type of colloidal system and, ultimately, to predict the system's viscosity. The results from the computational model developed are validated by comparing them with published experimental results. The model agrees well with experimentally determined viscosities of electrode ink materials at different concentrations and systems. Furthermore, the Z number derived from the Ohnesorge parameter was calculated to predict the jettability of the electrode slurry at different shear viscosity. It is worth noting that the Ohnesorge parameter can indicate whether a droplet will remain cohesive or break apart based on the balance between viscous and surface tension forces. The study found that analyzing the fluid's rheology can provide useful insights into its ability to form jets.