Microstructure implementation and analysis of dry-processed thick electrodes for high-energy-density lithium-ion batteries

Abstract

The increasing demand for high-energy-density lithium-ion batteries has encouraged the adoption of thick electrodes that enhance cell energy density by reducing the ratio of inactive components. While this strategy effectively boosts energy density, thick electrodes inevitably exhibit longer lithium-ion transport paths that result in lower capacity at the same C-rate and degraded rate capability. Moreover, conventional wet-processed electrodes encounter additional challenges, including uneven distribution of carbon–binder domains, delamination, and increased internal resistance, which worsen with increasing electrode thickness. These limitations highlight the urgent need for alternative electrode manufacturing strategies that can simultaneously deliver high energy density, reliable structural integrity, and scalable processability.

To overcome these issues, this study introduces a solvent-free dry electrode fabrication method that employs PTFE as a binder. The fabrication process is systematically divided into sequential unit operations—mixing, kneading, grinding, film formation, pressing, and lamination—each of which is tailored to a specific role by exploiting the unique fibrillation properties of PTFE. At each stage, intermediate product specifications are explicitly defined, ensuring reproducibility and process control. Through comprehensive physical and electrochemical analyses, we establish how PTFE content and fibrillation behavior dictate the microstructural evolution of dry electrodes. This study further demonstrates the decisive role of conductive agent selection in optimizing dry-processed electrodes for high-energy-density applications. By systematically applying various conductive agents, we show that porous spherical conductive agents are particularly effective in enhancing both electrical conductivity and lithium-ion diffusion, characteristics that are difficult to incorporate into conventional slurry-based wet processes. Electrode parameter analysis confirms that an optimized content of porous spherical conductive agents enables the fabrication of cathodes with areal capacities of 10–20 mAh/cm2 and a composite density of 3.65 g/cm3. These electrodes exhibit outstanding electrochemical performance, showing 88% capacity retention at 1 C and 80% retention after 418 cycles. Moreover, their scalability is validated through the successful demonstration of 1 Ah-class stacked pouch cells employing double- sided cathodes, fabricated entirely through sequential dry process equipment rather than manual assembly.

In summary, this study presents a hierarchical framework that spans material-, electrode-, and cell- level perspectives to address the challenges of thick electrode fabrication. By integrating fibrillation- based PTFE binder engineering with conductive agent optimization, we establish fundamental design principles and practical strategies for dry-processed thick electrodes. The findings not only improve the microstructural and electrochemical properties of electrodes but also pave the way for environmentally friendly, scalable, and high-performance electrode manufacturing processes for next-generation lithium-ion batteries.