The Japanese technology company Asahi Kasei Corp. introduces a new material solution for enhanced electric vehicle (EV) battery safety. A flame-retardant and highly flexible nonwoven fabric, LASTAN™ is an outstanding alternative to conventional materials for thermal runaway protection. It can be utilized in top covers, busbar protection sleeves, and other applications within the EV battery pack.

Although EVs 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 EV. Against this background, global OEMs seek to further raise the safety of EV batteries. Accordingly, the market for materials to prevent thermal runaway is expected to grow by some 15% annually from 2024 onward. Further expansion of demand is seen in the future (IDTechEX: “Fire Protection Materials for Electric Vehicle Batteries 2024–2034”).

In this context, there is increasing demand for materials in EV battery cover applications featuring excellent resistance against flames and particle blasts, as well as good electrical insulation properties. Generally, mineral-based materials are used as protection against thermal runaway at present. However, such materials tend to be heavy and brittle. Being stiff, these materials are difficult to adapt to complex shapes, making processability an issue for automotive OEMs.

Non-Mineral Flame-Resistant Fabric

Specifically, LASTAN™ is a non-mineral flame-resistant fabric made by air baking a special acrylic fiber at 200 to 300°C. It is characterized by high flame resistance and good electrical insulation, 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. With these exceptional characteristics, LASTAN™ has been used for many years as an optimal material for failure prevention and safety in various industries.

Withstanding 1,300°C Flames and Impact of 200 to 500µm Particles

Even by applying 1,300°C flame, 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 to 500µm. It also provides electrical insulating capacity of up to 3.5kV at a thickness of 1mm. LASTAN™ also features outstanding processability, being highly flexible while maintaining its performance characteristics in sheets as thin as 0.8mm. This makes it easily processed with ordinary tools, contributing to a simplified manufacturing process.

At present, Asahi Kasei manages an integrated production of LASTAN™ in Japan. Further, it 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 to 10, 2024, in Detroit, Michigan.

-20 September 2024-