Real-time Evaluation of Electrode Slurry Coating Conditions Critical for Battery Electrode Performance Now Possible – Rapid Identification of Optimal Conditions with Trace Samples Contributes to Efficient Battery Development and Resource Saving

Press Release Information Title: Real-time Evaluation of Electrode Slurry Coating Conditions Critical for Battery Electrode Performance Now Possible – Rapid Identification of Optimal Conditions with Trace Samples Contributes to Efficient Battery Development and Resource Saving Subtitle: Company Name: Industry: Body (First 8000 characters): [Summary and Key Points of Research]

We have established a method for rapidly evaluating the state of electrode slurry under different coating conditions, in real-time and with extremely small sample volumes.

Using this method, we demonstrated a clear inverse correlation between the electrical resistance of the slurry and the electrical resistance of the dried electrode.

This is expected to enable efficient development of new battery materials with fewer resources, accelerating R&D towards improved battery performance.

[Research Overview]

Associate Professor Isao Shirofuntani of the Department of Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, Mr. Taiyo Sekiguchi, a first-year master's student in the Advanced Chemistry program, Graduate School of Science and Technology, Tokyo University of Science, Dr. Hiroyuki Ueda of Deakin University, and Mr. Yoshifumi Yamagata and Mr. Keisuke Miyamoto of Anton Paar Japan K.K., have established a method for evaluating the coating conditions of paste-like electrode material (slurry, *1), which is crucial for manufacturing lithium-ion battery electrodes, using trace amounts of samples. This method is expected to improve the efficiency of design in battery development and contribute to performance improvement and resource saving.

When producing positive electrodes for lithium-ion batteries, it is essential to uniformly coat a metal foil with a slurry, which is a mixture of constituent materials dispersed in a solvent, to a uniform thickness (coating). Different coating speeds can cause changes in the state within the electrode material, significantly affecting electrode performance, thus requiring optimization of coating conditions. Traditionally, finding these optimal conditions required actually assembling batteries and conducting charge/discharge tests, which demanded vast amounts of time, materials, and cost.

This research group succeeded in evaluating the state of the positive electrode slurry in real-time under conditions replicating actual coating processes, using the previously developed rheo-impedance measurement method (*2, *1). They also demonstrated a clear inverse correlation between the electrical resistance of the slurry and the electrical resistance of the electrode, and elucidated the underlying structural differences. Furthermore, from correlation analysis with the state during coating, they successfully extracted promising parameters related to the differences in dried electrode structure and battery performance.

This method can determine the suitability of coating conditions with less than 1 mL of slurry per condition and within approximately 5 minutes of measurement. This allows for rapid narrowing down of promising coating conditions before assembling the battery. This research outcome is expected to lead to a significant reduction in the number of prototypes, material usage, and waste compared to conventional condition searches relying on empirical rules or actual measurements after battery assembly.

This research result was published online in the international academic journal "Journal of Power Sources" on April 30, 2026.

Figure 1. Overview of this research

[Background of Research]

Lithium-ion batteries, indispensable in modern society for smartphones, electric vehicles, and large-scale grid storage, primarily consist of a positive electrode, negative electrode, electrolyte, and separator. The positive electrode (+ electrode) is particularly important as it determines battery performance. It is produced by coating aluminum foil with a slurry, a mixture of active material, conductive additive, and binder in a solvent, and then drying it.

To maximize battery performance, it is crucial to uniformly disperse carbon black (*3), a conductive additive in the positive electrode, within the slurry and form a continuous conductive network (*4) in the dried electrode. Methods for evaluating slurry dispersion state have included particle size analysis, zeta potential measurement, and rheology (fluidity) measurement. However, all of these are static evaluations and could not directly link the behavior of carbon black, which dynamically rearranges during the coating process, with the dried electrode structure and battery performance.

Furthermore, the effect of coating speed on electrode structure and battery performance has largely not been quantitatively evaluated, and determining coating speed has practically relied on empirical rules in manufacturing sites. This led to problems such as prolonged development, material waste, and increased waste due to the need for numerous prototypes and battery evaluations to find optimal conditions.

[Details of Research Results]

To simulate the coating thickness in an actual electrode production line, an LFP (lithium iron phosphate, *5) positive electrode slurry was set in a rheometer with a 500 μm gap, and "rheo-impedance measurement" was performed. This method, previously developed by the same research group (reference), allows simultaneous measurement of electrochemical impedance while applying multiple shear rates (1.3 to 200 s-1) corresponding to coating speeds. This made it possible to evaluate the electrical properties of the slurry in real-time under conditions replicating an actual coating environment.

As a result of the measurements, it became clear that the electrical resistance of the slurry (R_slurry) does not change linearly with coating speed but shows a maximum value at intermediate speeds. This indicates that carbon black particles change their state depending on the coating speed during coating. Keywords: