Abstract
A team of researchers, affiliated with UNIST has made a significant breakthrough in developing an eco-friendly dry electrode manufacturing process for lithium-ion batteries (LIBs). The new process, which does not require the use of harmful solvents, enhances battery performance while promoting sustainability.
Led by Professor Kyeong-Min Jeong in the School of Energy and Chemical Engineering at UNIST, the research team has introduced a novel solvent-free dry electrode process using polytetrafluoroethylene (PTFE) as a binder. This innovative approach addresses the challenges associated with traditional wet-electrode manufacturing methods, which often result in non-uniform distribution of binders and conductive materials, leading to performance degradation.
Figure 1. Overview of dry electrode manufacturing process: unit processes, equipment, and intermediate products used in this study.
The dry electrode process is divided into four stages: granule formation, film formation, rolling, and lamination. The team optimized the process conditions by evaluating the physical, electrical, and electrochemical properties of semi-finished products at each stage. The results showed that a high-extrusion-ratio PTFE binder can produce an electrode film with high strength even with low energy consumption, leading to improved microstructure and power characteristics.
Figure 2. Schematic diagram showing the fibrillation process of the PTFE binder with kneading time, photographs of the bulk shape, and SEM images of the microstructure of the electrode dough (F-208 2%).
In LIBs, binders play a crucial role in connecting active materials and electrons. The study revealed that the type and content of PTFE binders significantly impact the output characteristics of dry electrodes. The researchers identified an optimal formulation of NCM811/PTFE/carbon black (CB)/carbon nanotube (CNT) = 96/2.0/1.8/0.2, which demonstrated exceptional discharge rate capability of 80% at a 0.5 C-rate (5 mA/cm2) under demanding conditions.
"This breakthrough will contribute to commercialization by providing a scalable and practical solution for mass production," emphasized Professor Jeong. "We believe that our study will pave the way for environmentally friendly and efficient electrode manufacturing for future energy storage applications."
Figure 3. Film formation - roll mill - electrode film. (a) Schematic of the manufacture of electrode film from electrode granules using a roll mill. (b) Photographs of the electrode film by type and amount of PTFE after roll milling.
The findings of this research have been published in the July 2024 issue of Chemical Engineering Journal. It has been carried out through the support of the National Research Council of Science and Technology (NST) and the Ministry of Science and ICT (MSIT).
Meanwhile, the Korea Institute of Energy Research (KIER) and Hanwha Co., Ltd. have also partnered with UNIST to develop dry electrode-specific manufacturing equipment and demonstrate its commercial viability from the second half of this year. The team is planning to further improve the output characteristics of thick electrodes by exploring various materials through follow-up research. With this innovative technology, electric vehicles and electronic devices are expected to become more sustainable in the future.
Journal Reference
Hyeseong Oh, Gyu-Sang Kim, Byung Un Hwang, et al., "Development of a feasible and scalable manufacturing method for PTFE-based solvent-free lithium-ion battery electrodes," Chemical Eng. Journal, (2024).
