- Published in an international journal

A research team led by Professor Cho Gye-Yong of the Department of Energy and Chemical Materials Engineering at Pukyong National University has developed an active separator technology that can enhance the stability and lifespan of next-generation high-energy lithium batteries. This technology is particularly effective in mitigating lithium-ion concentration gradients and electrode degradation, which commonly occur in high-energy batteries, especially from the separator perspective.  

Lithium-based batteries are widely regarded as a core technology for next-generation energy applications, including electric vehicles (EVs) and energy storage systems (ESS). However, during repeated charge-discharge cycles, imbalances in ion transport and electrolyte decomposition reactions can occur, leading to performance degradation and safety issues. In particular, byproducts such as hydrogen fluoride (HF) generated during the decomposition of the electrolyte salt (LiPF6) are known to continuously degrade internal battery interfaces.  

To address these issues, the research team designed an active separator structure capable of controlling the transport behavior of electrolyte anions (PF6-). This separator is based on a fluorinated polymer material with high electronegativity on its surface, combined with amine-based functional groups exhibiting cationic characteristics. Through this design, it electrostatically regulates the transport properties of PF6- anions in the electrolyte and controls their electrical state, thereby limiting the formation of PF5, which exhibits strong acidity. As a result, it effectively suppresses continuous electrolyte decomposition reactions.  

Analysis of the operating mechanism of this separator revealed that, compared to conventional polypropylene (PP) separators, the lithium-ion transference number increased by approximately twofold, while the lithium-ion diffusion coefficient improved by about threefold. In addition, the interfacial layers (SEI/CEI) formed between the electrode and electrolyte were found to maintain a thin and uniform structure even after long-term cycling.  

Owing to these characteristics, batteries incorporating this separator demonstrated stable performance not only under high-temperature and high-voltage conditions, but also during long-term charge-discharge cycles across various cathode materials. The batteries also operated stably under high-rate charge-discharge conditions, and symmetric cell experiments using a lithium metal anode confirmed long-term stability with uniform lithium plating formation.  

Park Jang-Woo, the first author of the study, stated, “This research demonstrates that separators can go beyond acting as a physical barrier and actively control the ionic environment inside batteries.” He added, “While solutions to this issue have traditionally been proposed at the electrode and electrolyte levels, this study presents a new design strategy in which the separator regulates the behavior of electrolyte anions, reduces side reactions within the battery, and efficiently guides ion transport, thereby enhancing the stability of next-generation high-energy lithium batteries.”  

This research was supported by the Ministry of Trade, Industry and Energy and the National Research Foundation of Korea. The findings were published online in March 2026 in the international journal Advanced Functional Materials under the title 'Active Separators Featuring PF6- Anion-Regulating Interface for Long-term Stable Li-based Batteries.'