Polymeric conducting binders have increasingly become a subject of significant research interest due to their dual roles as both a binder and a conducting agent. This dual functionality not only increases the proportion of active materials in the electrode but also elevates the volumetric energy density of current Li-ion batteries. In this study, we explore the potential of a composite of PEDOT:PSS and polyethylene glycol (PEG) as a high-performing binder for silicon anodes. This highly conductive PEDOT:PSS, enhanced by the addition of PEG polymer, displays exceptional electrochemical characteristics, including superior C-rate, Li-ion diffusivity performance, and extended cycle endurance. Of particular interest are the enhanced mechanical properties bestowed by the plasticizing effect of the PEG polymer. This improvement aids the Si anode in resisting pulverization during successive discharge and charge cycles. As a result, this enables extended cyclability without the creation of anode cracking. Additionally, the use of operando optical microscopy allows for the direct observation of lithiation kinetics within the PEDOT:PSS/PEG binder. This revealed a uniform color change with restrained volume expansion, demonstrating the successful operation of the binder. Consequently, the bifunctional PEDOT:PSS/PEG binder shows promise as a robust strategy for the next generation of high-performance lithium-ion battery binders.
A research team, jointly led by Professor Seok Ju Kang and Professor Hyun-Wook Lee in the School of Energy and Chemical Engineering at UNIST has successfully developed a novel binder technology that promises to revolutionize battery performance. By combining PEDOT:PSS and polyethylene glycol (PEG) polymers, the research team has achieved a binder with an impressive 72 times higher electrical conductivity, opening up new possibilities for high-performance lithium-ion batteries. According to the research team, this breakthrough in binder technology holds tremendous potential for advancing battery performance and enabling the development of high-energy density lithium-ion batteries.
Traditionally, binders have served as adhesives between electrodes and conductive materials in batteries. However, their relatively low electrical conductivity has limited their effectiveness. This breakthrough research introduces a high-conductive polymer binder that eliminates the need for additional conductive materials, thus enhancing the energy density of batteries.
“By developing high-electrical conductivity polymer binders using commercially available polymers, we can significantly enhance the performance of silicon cathode-based secondary batteries,” said Professor Kang. “The developed binder mixture demonstrated approximately 72 times higher electrical conductivity than previous binders.”
In addition to its exceptional electrical conductivity, the newly developed binder exhibits remarkable mechanical properties. It effectively accommodates the expansion and contraction of the battery volume, overcoming the typical challenges associated with silicon cathodes. Notably, even after 100 charging and discharging cycles, the battery maintained 75% of its initial capacity, highlighting the binder’s high performance and stability.
“Our research team has achieved a silicon cathode with high energy density by improving electrical conductivity and mechanical properties through effective phase change of PEDOT:PSS,” emphasized Nyung Joo Kong, the first author of the study.
“The real-time lithium storage experiments using the developed polymer binders further confirmed their high stability, positioning them as a significant advancement in silicon cathode research,” noted Professor Lee.
The study, published online on November 17, 2023, in Energy Storage Materials, was conducted with the support of the National Research Foundation (NRF) of Korea, the Korea Institute of Energy Technology Evaluation and Planning (KETEP), and the Ministry of Science and ICT (MIST).
Nyung Joo Kong, Myeong Seon Kim, Jae Hyun Park, et al., “Promoting homogeneous lithiation of silicon anodes via the application of bifunctional PEDOT:PSS/PEG composite binders,” Energy Stor. Mater., (2023).