A new dry-process electrode manufacturing technology for secondary batteries has been developed, offering both durability and high performance.
The Korea Institute of Energy Research announced on December 3 that a joint research team led by Dr. Kyu-Jin Song from the Korea Institute of Energy Research, Dr. Kwon-Hyung Lee from the University of Cambridge, and Professor Tae-Hee Kim from the University of Ulsan has developed a new dry-process electrode manufacturing technology for secondary batteries.
(From left) Dr. Kyu-Jin Song and Researcher Hyung-Seok Shim from the Korea Institute of Energy Research, Dr. Kwon-Hyung Lee from the University of Cambridge, and Professor Tae-Hee Kim from Ulsan University. Provided by Korea Institute of Energy Research
The developed technology is a dry-process manufacturing method with a 'dual-fibrous' structure, which simultaneously forms fine 'thread'-like and thick 'rope'-like fiber structures inside the electrode. This is significant because it addresses both the low mixing strength and performance degradation issues of conventional dry processes.
Manufacturing electrodes for secondary batteries is typically divided into wet and dry processes, depending on whether a solvent is used. The wet process uses a binder dissolved in a solvent as an adhesive, allowing for uniform mixing of electrode materials. In particular, it is mainly used in electrode manufacturing processes due to its high process reliability and advantages in achieving high performance.
However, the use of toxic organic solvents in the wet process leads to significant environmental burdens, and the drying and solvent recovery steps are time-consuming, resulting in high production costs.
Recently, there has been a growing emphasis on developing dry-process technologies to overcome these limitations. The dry process does not use solvents, enabling faster processing speeds and reducing environmental pollution and energy consumption.
However, the absence of solvents to dissolve the binder means that only limited types of binders, such as polytetrafluoroethylene (PTFE), which physically hold materials together like fibers, can be used.
For the same reason, it has been difficult to uniformly mix electrode materials in the dry process, resulting in low mixing strength and making it challenging to achieve both high performance and durability in the finished battery.
Schematic of the 'multi-stage process' developed by the joint research team. Provided by Korea Institute of Energy Research
To address this, the joint research team devised and implemented a method to control the physical structure of the PTFE binder, rather than changing the binder material itself, to create a 'dual-fibrous' PTFE binder structure.
First, they designed a multi-stage process that divides the binder addition step from a single stage into two stages. By adding a small amount of binder for the first mixing, they form a fine 'thread'-like fiber network that tightly connects the active material and conductive agent. Then, with the second mixing, they add the remaining binder, allowing a thick and robust 'rope'-like fiber structure to form while maintaining the existing fiber network.
The resulting fine 'thread' fiber network evenly disperses the active material and conductive agent, ensuring uniform reactions and improving battery performance.
The thick 'rope' fibers, on the other hand, bind the entire electrode firmly, greatly increasing its strength and mechanical stability, while also enhancing the durability required for mass production processes.
As a result, the joint research team confirmed that the electrode exhibited fast and uniform reaction rates and resistance characteristics across all regions. This is a key factor in minimizing energy loss during battery operation, preventing localized performance degradation, and thereby extending the overall battery lifespan.
Dr. Song stated, "This research is significant in that we have established a unique process technology capable of simultaneously solving the core challenges of electrochemical uniformity and mechanical durability in dry-process electrodes. We expect that these results will enhance the price competitiveness of the secondary battery industry and be applied to electric vehicles and energy storage systems (ESS) that require high energy density in the future."
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