< The research team. From left: Ph.D. student Geunjung Lee, Dr. Rak Hyeon Choi, Professor Hye Ryung Byon, and Professor Dong Ki Yoon (KAIST Department of Chemistry). >
When using electric vehicles or smartphones, users often experience inconvenience from long charging times and gradually shortening battery life. To increase charging speed and extend usage time, next-generation batteries with high energy density are essential. However, fast charging has had limitations because deposits can accumulate inside batteries, degrading performance and even increasing the risk of fire. A Korean research team has developed a new foundational technology to address this problem by creating a "highway" through which lithium ions can move rapidly inside a battery.
KAIST (President Choongsik Bae) announced on November 9 that a joint research team led by Professors Dong Ki Yoon and Hye Ryung Byon from the Department of Chemistry developed a next-generation battery separator technology that precisely controls lithium-ion transport pathways by regulating the molecular alignment of liquid-crystalline polymers.
Lithium metal batteries can store more energy than conventional batteries. However, during charging, lithium can accumulate in sharp, branch-like structures known as "dendrites." This phenomenon has been a major cause of reduced battery life and can damage the internal separator, potentially leading to explosions.
< Schematic showing how the alignment of liquid-crystalline polymers affects lithium-ion transport pathways and dendrite formation. >
< Schematic of the synthesis of PEG-functionalized liquid-crystal molecules and the fabrication of planar-aligned and vertically aligned liquid-crystalline polymer separators by controlling molecular alignment. >
The research team sought to solve this problem using liquid crystal materials, which combine the ordered characteristics of solids with the fluidity of liquids. Because the orientation of liquid crystal molecules can be altered through surface treatment and other methods, the researchers used this property to regularly align the pathways through which lithium ions travel.
Based on this liquid-crystal alignment control technology, the team also created a porous liquid-crystalline polymer separator containing nanoscale pores. Polyethylene glycol (PEG) chains, which facilitate lithium-ion transport, were incorporated into the separator. In particular, the researchers freely controlled the alignment direction of the liquid-crystal molecules either vertically or horizontally and compared the resulting lithium-ion transport characteristics.
The results showed that the liquid-crystalline polymer separator with vertically aligned molecules formed a kind of "highway" that allowed lithium ions to move directly toward the electrodes. Compared with a horizontally aligned separator, it reduced the tortuosity of the ion transport pathway by approximately 2.5-fold, enabling lithium ions to move much faster and more uniformly. This effectively suppressed dendrite formation and significantly improved stability.
The research team applied the newly developed separator to an actual lithium metal battery and verified its fast-charging performance. Even under demanding fast-charging conditions at a high charging rate of 4 C*, the battery retained 94% of its initial capacity after 100 charge-discharge cycles. This demonstrates that controlling the molecular alignment of liquid-crystalline polymers can be a highly effective strategy for improving both the charging speed and lifespan of next-generation batteries.
*4C charging rate: A rate at which a battery can theoretically be fully charged in approximately 15 minutes based on its rated capacity. C is a unit indicating the charging and discharging rate of a battery: 1C corresponds to 1 hour, 2C to 30 minutes, and 4C to 15 minutes.
< Ionic conductivity, porosity, tortuosity of the ion transport pathway, and activation energy of liquid-crystalline polymer separators with different alignments. >
Professor Dong Ki Yoon said, "This study demonstrates that controlling the molecular alignment of liquid-crystalline polymers can be used to efficiently design lithium-ion transport pathways and thereby improve battery performance and stability," adding, "We expect this approach to contribute to the development of high-energy-density next-generation battery technologies, for which long driving ranges and rapid charging are essential."
Geunjung Lee, a Ph.D. student at KAIST, and Dr. Rak Hyeon Choi participated in the study as co-first authors, while Professors Hye Ryung Byon and Dong Ki Yoon participated as co-corresponding authors. The research was published in the international journal ACS Nano in September 2026.
Paper title: Directional Li+ Flux Control via Liquid-Crystalline Polymer Separators for Fast-Charging Lithium Metal Batteries, DOI: https://doi.org/10.1021/acsnano.6c09591
Author information: Geunjung Lee†, Rak Hyeon Choi†, Geonhyeong Park, Juri Kim, Younwoo Kim, Hye Ryung Byon*, Dong Ki Yoon*; † co-first authors, * corresponding authors.
This research was supported by the Mid-Career Researcher Program of the Ministry of Science and ICT and the National Research Foundation of Korea, as well as the GIST InnoCORE Program.
