According to the Teijin group company, until now aramid nanofibers have been produced only in laboratories, so this commercially viable product represents a significant step forward in the evolution of a promising new material.
Teijin Techno Products’ nanofiber, which is uniformly sized with a diameter of just several hundred nanometers, is based on Teijin's proprietary Teijinconex heat-resistant meta-aramid. It will be marketed in the form of nonwoven sheet for separators in lithium ion batteries (LIBs). Commercial production is targeted at 2014.
Teijin Techno Products’ highly heat-resistant aramid nanofiber sheet maintains its shape even at 300°C. It is also highly resistant to oxidation. Such features are expected to enhance the safety of high-power, high-capacity, energy-dense LIBs for vehicles and stationary storage, offering significant advantages over conventional separators in terms of reducing the risk of ignition in high-capacity, energy-dense applications.
Other features that Teijin Techno Products expects to achieve with aramid nanofiber nonwoven sheet for battery separators include:
• High porosity promotes smooth mobility of the electrolyte, resulting in higher output and faster charging.
• Large surface area, a feature of nanofibers, as well as high porosity, hold the electrolyte effectively to maintain battery performance at low temperatures, when ion conductivity drops.
• As a nonwoven sheet, absorbs electrolyte more rapidly than conventional polyolefin-based separators, helping to shorten the time required to pour electrolyte into the battery, thereby reducing the production cost of large batteries.
Teijin Techno Products expects to develop other applications for its thin, heat-resistant aramid nanofiber sheet, such as separators for capacitors; high-performance, heat-resistant filters; and heat-resistant cleaners for office automation equipment.
The Teijin Group has also developed two types of separators based on porous polyethylene film, one coated with a fluorine-based compound for high heat-resistance and adhesion to polymer electrolyte, and the other coated with Teijinconex meta-aramid for excellent heat-resistance and dimensional stability, both of which will be commercialized in June under the LIELSORT brand. The addition of aramid nanofiber sheet will further strengthen Teijin's presence in the high-end LIB separator market.