POSTECH Unveils Conductive Agent That Extends Silicon Battery Lifespan
A material that extends the lifespan of silicon batteries has emerged. A research team led by Professor Kim Won-bae of the Department of Chemical Engineering and the Department of Battery Engineering at Pohang University of Science and Technology (POSTECH) announced on the 8th that it has developed a functional conductive agent that improves the lifespan and stability of silicon batteries. The achievement resolves the volume expansion problem of silicon, a next-generation anode material.
The POSTECH researchers added a function to the conductive agent—which helps electrons move smoothly inside the battery—that suppresses the chemical reactions (interfacial reactions) occurring on the silicon surface that degrade performance. The functional conductive agent developed by the team, composed of Professor Kim Won-bae (Chemical Engineering·Battery Engineering), Dr. Kang Song-gyu (Chemical Engineering), and Kim Hyun-ju (Battery Engineering), consists of carbon nanofibers (CNF)—carbon fibers thinner than a human hair—functionalized with sulfonic acid groups (-SO₃H).
Silicon, which theoretically offers higher energy storage capacity than graphite, is being studied as a next-generation secondary battery anode material. However, its volume changes dramatically with each charge and discharge cycle, making it difficult to secure long-term performance. Repeated expansion and contraction causes cracks in the particles, weakening electrical connections and depleting the electrolyte and lithium, which reduces battery capacity and lifespan.
The research team took an approach that expands the very role of the conductive agent. They designed it by bonding sulfonic acid groups to carbon nanofibers to strengthen interactions with silicon particles and even control the interfacial reactions on the electrode surface. The sulfonic acid groups bind strongly to the silicon surface, helping maintain electrical connections between the carbon nanofibers and silicon even during charge and discharge. Their high polarity also draws the electrolyte additive FEC toward the silicon, enabling the formation of a stable solid electrolyte interphase (SEI) rich in lithium fluoride (LiF).
Silicon batteries incorporating this conductive agent retained 94.2% of their initial capacity after 300 charge and discharge cycles. The results were largely unchanged even under conditions where a high loading of active material—close to commercial battery levels—was applied to the electrode. The team achieved an areal capacity of 10.2 mAh cm⁻², far exceeding the 5 mAh cm⁻² level of existing silicon batteries.
Professor Kim Won-bae of POSTECH explained, "The significance lies in adding a function that controls interfacial reactions to the conductive agent, which has traditionally been used as an auxiliary material for ensuring conductivity." The research findings were published as a cover article in the international journal Advanced Functional Materials. The research was supported by the Leader Researcher Center (ERC) Program and the Mid-Career Researcher Program of the Ministry of Science and ICT and the National Research Foundation of Korea, as well as the Battery Specialized Graduate Program of the Ministry of Trade, Industry and Energy.
