Technological breakthrough in carbon nanotube applications for battery dry process

A research team led by Dr. Joong Tark Han at the Korea Electrotechnology Research Institute (KERI) Nano Hybrid Technology Research Center has developed the world’s first technology for producing highly dispersible carbon nanotube (CNT) powder, which can be easily applicable to environmentally-friendly secondry battery dry processes.

CNTs are a novel material with a tensile strength 100 times that of steel and an electrical conductivity comparable to that of copper. They are formed by hexagonal carbon chains in long cylindrical shapes. CNTs are one-dimensional nanomaterials that are more flexible and electrically conductive than carbon black, which is used as a conductor in secondary batteries.

When used as a conductive additive^* in secondary batteries, the addition of CNTs can significantly increase the energy density. However, CNTs have a strong tendency to aggregate with each other, resulting in a tangled structure that does not mix well with other materials in the secondary battery, such as binders and active materials. Especially in the dry process, it is necessary to mix CNTs uniformly with other materials in solvent-free conditions, which has been one of the challenges for the battery industry.
^{* Conductive additives facilitate the movement of electrons between active materials to produce electrical energy. The first step in the secondary cell process is “mixing," which involves mixing the active material, conductive additive, and binder that holds them together to create a mixture.}

Dr. Han’s team achieved a breakthrough by developing a technology that minimizes aggregation and facilitates dispersion in dry processes by producing higly dispersible CNTs powder. After years of research, the team successfully controlled the small bundles of CNTs to remain dispersed in powder form.

This opens the way to manufacturing high-capacity cells by making conductors from long CNTs with a one-dimensional structure, even in a challenging dry process. Highly conductive CNTs that are well dispersed without the use of solvents can make a significant contribution to the performance of secondary batteries by electrically connecting the other materials inside.

“The dry process is environmentally friendly as it does not use toxic solvents^*, eliminates the need for solvent recovery, simplifies the process, and reduces production costs. That is why this technology is drawing attention from global electric vehicle manufacturers,” said Dr. Han. “We’re the first in the world to achieve the effective dispersion of CNTs to create conductive additives in dry processes. This technology will greatly aid in securing a significant technological lead in secondary battery technology.”
^{* In the wet process, cathodes are manufactured by dissolving the active materials, conductive additives, and binders in a toxic organic solvent, which is then evaporated at a high temperature of over 200 degrees for over 12 hours. Large amounts of carbon dioxide are produced from this process.}

Based on this achievement, KERI has already filed a domestic patent application and is validating the "high-dispersibility CNT Powder production technology" for various applications, including high-capacity thick-film anodes/cathodes. In addition, Dr. Han expects that this achievement will attract attention from related industries such as lithium-sulfur batteries and all-solid-state batteries, which require a dry process as next-generation batteries, and plans to identify demanding companies to transfer the technology.

This research project was conducted with the support of KERI’s Basic Research Project Funding and the National Research Council of Science and Technology’s Creative Convergent Research Support Program.

<KERI is a government-funded research institute under the National Research Council of Science and Technology of the Korean Ministry of Science and ICT.>