Fire protection of lightweight EV battery cases using nanotechnology (PFP_Nano)

The reduced road and air transport during the COVID lockdown resulted in visibly clearer and cleaner air and has made many assess the impact of transport on the air that we breathe. Electric propulsion for cars, buses, trains, and planes supports the **transition** to **lower emission** transport. The battery of choice for these applications are Lithium Ion Batteries (LIB). For safe use, the battery packs must be maintained within a defined voltage and temperature window; limits can be exceeded by damage (accidents, rapid deceleration etc), excessive external temperatures, charging too quickly, overcharging or manufacturing defects. Chemical reactions may be triggered internally leading to a short circuit or increase in the temperature which can lead to thermal runaway and the LIBs catching fire. Hence, there is a need to provide lithium ion battery fire containment for as long as possible to aid occupant evacuation in auto, marine, rail and aerospace sectors.

Most LIB casings are made from metal (steel, aluminium) providing mechanical support to the cells. These battery casings are typically heavy; lighter versions can be made using carbon-fibre-reinforced polymers (CFRP) and several prototype CFRP battery cases have been developed. However, there are no known solutions that combine lightweight CFRP structural battery cases with intrinsic fire containment.

HIVE is an innovation-based business developing disruptive composite materials technologies with significant potential for growth and scale-up. Hive have a carbon-nanotube (CNT) based solution that can be incorporated into resins and/or deployed on the surface of structural CFRP to impart multi-functionality through significantly improved fire and thermal conductivity whilst maintaining structural performance. When coated on a composite material, preliminary tests have shown the time to ignition of the parent material is doubled. Thermal conductivity of the composite materials will also be modified for better thermal management of the batteries. The weight of the CNT materials either within the matrix or on the surface of the composite battery cases will add a few grammes to the overall composite battery case but has the opportunity to double the containment time for a battery fire, thereby adding passive safety for occupants at minimal weight and cost. Use of composite battery cases will therefore reduce overall battery pack weight compared with metallic versions.

This project will develop a **cost-effective passive fire protection material system** for composite battery cases using a unique format of Carbon nanotube (CNT) materials and will generate the data to demonstrate the performance of these materials for implementation across multiple transport sectors.