Better batteries begin with optimized slurry processing

Lithium-ion batteries are essential to modern life, powering electric vehicles, portable electronics, and energy storage systems. While major advances have improved battery materials, important challenges remain in manufacturing, especially in preparing the electrode slurry, a mixture that directly affects electrical conductivity, stability, and overall battery performance.

Studying these slurries is difficult because most techniques examine them under static conditions, whereas real manufacturing involves strong shear forces during mixing and coating. Under shear, conductive additives like carbon black can rearrange, changing the internal network that controls how easily electrons move through the electrode. These effects are hard to capture with conventional methods.

Now, researchers from Tokyo University of Science (TUS), Japan, have applied and extended rheo-impedance spectroscopy to evaluate electrode slurries under coating-like shear conditions. The technique, previously developed by the same group, integrates controlled shear deformation with electrochemical impedance spectroscopy (EIS), which measures how easily electrical signals pass through a material. This allows researchers to observe how conductive networks evolve inside complex battery slurries while the slurry is being processed.

The findings were made available online on April 30, 2026, and will be published in Volume 679 of the Journal of Power Sources on July 01, 2026. The study was led by Associate Professor Isao Shitanda from the Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science. The research team included Taiyoh Sekiguchi, a first-year master’s student; Hiroyuki Ueda from Deakin University, Australia; and Yoshifumi Yamagata and Keisuke Miyamoto from Anton Paar Japan.

“By reproducing shear conditions close to those used during electrode coating and evaluating the slurry in situ, we can relate the slurry state to the conductive network formed after drying and to battery performance. This makes it possible to identify promising coating conditions before assembling cells,” says Dr. Shitanda. Because the method builds on established techniques such as rheometry and electrochemical impedance spectroscopy, it could be adopted relatively quickly in research and process-development laboratories after calibration for specific slurry formulations.

The researchers applied this method to lithium iron phosphate (LiFePO₄) cathode slurries, which are widely used in lithium-ion batteries. Using a rotational rheometer, they applied controlled shear forces similar to those experienced during industrial coating. At the same time, they measured the slurry’s electrical response using EIS. The experimental setup closely replicated real manufacturing conditions, including a coating thickness of 500 micrometers.

The slurry consisted of LiFePO₄ as the active material, acetylene black as the conductive additive, and a polymer binder dissolved in a solvent. The team tested a range of shear rates from 1.3 to 200 s^-1 to simulate different coating speeds. After shear testing, the slurries were dried and converted into electrodes, which were then analyzed using microscopy techniques and assembled into battery cells for performance testing.

Their results showed a clear connection between how the slurry was processed and how the battery performed. As the shear rate increased, the internal structure of the slurry changed in a non-linear way. At low shear rates of around 1.3 s^-1, conductive additives remained clustered, leading to poor electrical connectivity. At very high shear rates up to 200 s^-1, the conductive network became overly fragmented, reducing performance. However, at an intermediate shear rate of around 50 s^-1, the additives were evenly distributed while maintaining strong connections, creating an optimal conductive network.

Electrodes made under these conditions showed lower resistance, improved charge–discharge performance, and better cycle stability. This demonstrates that there is an optimal “sweet spot” in processing conditions that balances breaking up particle clusters with maintaining electrical pathways. While these findings highlight the potential of the method to improve electrode performance, further validation across different material systems and cell designs will be necessary to confirm its broader applicability.

“This method can identify promising coating conditions using less than one milliliter of slurry, with each measurement completed in about five minutes,” says Dr. Shitanda.

The method offers several advantages: First, it replaces trial-and-error approaches with direct measurements to identify optimal slurry processing conditions. Second, it enables prediction of the electrode structure and battery performance directly from the slurry state during coating. This could accelerate battery development, reduce waste, and improve overall manufacturing efficiency as the demand for lithium-ion batteries continues to grow.

Reference
DOI: https://doi.org/10.1016/j.jpowsour.2026.240175

About The Tokyo University of Science
Tokyo University of Science (TUS) is a well-known and respected university, and the largest science-specialized private research university in Japan, with four campuses in central Tokyo and its suburbs and in Hokkaido. Established in 1881, the university has continually contributed to Japan's development in science through inculcating the love for science in researchers, technicians, and educators.

With a mission of “Creating science and technology for the harmonious development of nature, human beings, and society," TUS has undertaken a wide range of research from basic to applied science. TUS has embraced a multidisciplinary approach to research and undertaken intensive study in some of today's most vital fields. TUS is a meritocracy where the best in science is recognized and nurtured. It is the only private university in Japan that has produced a Nobel Prize winner and the only private university in Asia to produce Nobel Prize winners within the natural sciences field.

Website: https://www.tus.ac.jp/en/mediarelations/

About Associate Professor Isao Shitanda from Tokyo University of Science
Dr. Isao Shitanda graduated from Tokyo University of Science (TUS) in 2001 and received a Ph.D. from The University of Tokyo, Japan, in 2006. Since 2020, he has served as an Associate Professor at the Department of Pure and Applied Chemistry at TUS, leading the Shitanda Lab. Dr. Shitanda specializes in electrochemical micro-/nanosystems, physical and analytical chemistry, bio-related chemistry, and environmental chemistry, among other fields. He has published over 200 papers and holds 10 patents. He has received multiple awards for his contributions, including the "Supplemental Cover of Langmuir 2025" and "Bimonthly Most Downloaded Papers 2024."

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