South Korean researchers develop technology to optimize hybrid cathode materials to advance commercial development of all-solid-state batteries

According to foreign media reports, the research team led by Dr. Yoon Cheol Ha of the Next Generation Battery Research Center of the Korea Electric Research Institute (KERI) and Professor Byung-Gon Kim of the Department of Applied Chemistry of Kyung Hee University, and the research team led by Professor Janghyuk Moon of the School of Energy System Engineering of Chung-Ang University, have jointly developed a technology that can optimally mix the cathode material of all-solid-state batteries with sulfide solid electrolytes, aiming to meet the challenges of commercializing all-solid-state batteries. This research result has been published in the journal Energy Storage Materials.

Image source: KERI

All-solid-state batteries have become a hot topic as a next-generation battery technology due to their extremely low risk of fire or explosion. However, compared with traditional batteries based on liquid electrolytes, all-solid-state batteries require more advanced technologies due to their solid-state characteristics, making their manufacture more challenging.

It is well known that effective mixing and dispersion of cathode active materials with solid electrolytes, conductive additives and binders is one of the challenges in manufacturing composite electrodes. Its manufacturing must meet stringent conditions, such as creating channels (paths) that promote efficient transport of electrons and lithium ions and ensuring low interfacial resistance at the cathode-electrolyte interface.

Currently, there are two main approaches to mixing cathode materials and solid electrolytes: one is to simply mechanically mix them under wet or dry conditions to a thickness of tens to hundreds of micrometers (millionths of a meter), and the other is to use a core-shell structure approach, which is to wrap the surface of the cathode material with a solid electrolyte. However, these existing methods have challenges in ensuring the movement of electrons or ions and forming a low-resistance interface.

To solve this problem, the KERI and university research teams adopted a method of partially coating the surface of the cathode active material with a solid electrolyte.

Since sulfide solid electrolytes are sensitive to oxygen and moisture and will deteriorate if used improperly, the research team developed a blade mill, a special device that can use inert gas that does not cause chemical reactions. This enabled the researchers to study various types of solid electrolyte coating structures and test and verify the optimal mixing ratio and process conditions with the cathode active material.

The research team conducted various simulations to collect a large amount of data, demonstrating improvements in active material utilization (actual capacity compared to theoretical capacity) and rate capability (fast charge/discharge compared to low current charge/discharge), and then applied the results to a prototype (pouch cell) to verify the performance of the all-solid-state battery.

Dr. Yoon Cheol-Ha said, "For all-solid-state batteries to be widely adopted, it is crucial to improve the performance of the solid electrolyte itself and reduce its cost. However, at the same time, it is also important to effectively create a composite electrode that promotes the smooth flow of ions and electrons in the structure design and manufacturing process technology. By using a composite material, that is, partially coating the solid electrolyte on the cathode active material in an optimal ratio, we can enhance the functionality of the electrode and significantly improve the performance of all-solid-state batteries."

KERI has obtained the relevant patents for this technology and is looking for potential customers and seeking commercialization. KERI believes that this achievement will receive great attention from all-solid-state battery material and equipment manufacturers.