This technology involves coating a porous support with a mixture of cellulose nanofibers, which form a continuous chain-entangled structure, and cellulose nanocrystals, which act as a dispersed phase. This allows for the simultaneous achievement of thermal stability, puncture strength, and air permeability in a separator without the need for inorganic particles.
Conventional inorganic particle coating methods often suffer from reduced air permeability due to the use of acrylic or rubber-based adhesives. While using cellulose nanocrystals alone can improve puncture strength, it significantly lowers air permeability, leading to a trade-off that impairs ionic conductivity.
This technology forms a cellulose coating layer using a solvent mixture of water and an organic solvent with a higher boiling point, such as NMP, which creates micropores within the coating layer during the drying process. This ensures high air permeability while maintaining excellent puncture strength and thermal stability. Applicable to high-rate cells for fast charging and large-scale cells for energy storage systems, this technology achieves both an air permeability of Gurley 600 s/100cc or less and a puncture strength of 5 N or more in a single separator.
This invention was developed with support from the Korea Forest Service for the design and manufacturing technology of nanocellulose-coated separators.
US2024-0178520A1
