Asahi Kasei is introducing Lastan,  a flame-retardant and highly flexible nonwoven fabric, as an alternative to conventional materials for thermal runaway protection in electric vehicle (EV) batteries.

It can be used in top covers, busbar protection sleeves and other applications within the EV battery pack.

Although electric vehicles are becoming more common worldwide, battery safety is still a major concern for many car users. According to the latest Asahi Kasei Automotive Consumer Survey, 34% of non-EV owners in China see improved safety as a primary consideration in buying an electric vehicle. Against this background, global OEMs are seeking to further raise the safety of EV batteries, and the market for materials to prevent thermal runaway is expected to grow by some 15% annually from 2024.

In this context, there is increasing demand for materials in EV battery cover applications with excellent resistance against flames and particle blasts, as well as good electrical insulation properties.

While mineral-based materials are generally used as protection against thermal runaway at present, such materials tend to be heavy and brittle. Being stiff, these materials are also difficult to adapt to complex shapes, making processability an issue for automotive OEMs.

 Lastan is a non-mineral flame-resistant fabric made by air baking a special acrylic fibre at between 200-300°C. It is characterised by high flame resistance and good electrical insulation – properties which are further improved by a special coating process that also augments abrasion resistance. This allows the material to provide effective protection against particle bombardment from venting gas. Grades of Lastan have been used for many years as an optimal material for failure prevention and safety in various other industries.

Even when a 1,300°C flame is applied, the temperature on the opposite side of Lastan remains below 400°C.

While a limiting oxygen index (LOI) value of 27 or higher is generally considered to indicate flame retardance, this material has an LOI value of 50 or higher. In UL94 flame retardance testing, Lastan has obtained the highest rating of 5VA. No holes are formed in Lastan even when it is exposed to a flame of 1,300°C for one minute.

In addition to its high flame resistance, Lastan is resistant to high-pressure impact by particles of 200–500 µm. It also provides electrical insulating capacity of up to 3.5 kV at a thickness of 1mm. Lastan is also highly flexible while maintaining its performance characteristics in sheets as thin as 0.8 mm. This makes it easily processed with ordinary tools, contributing to a simplified manufacturing process. 

Having integrated production of Lastan in Japan, Asahi Kasei is considering production in the United States and other countries in the future. The company will exhibit the new Lastan grade at the North American Battery Show from October 7-10, 2024, in Detroit, Michigan.

www.asahi-kasei.com