Plastics Pave Path to Safer, Lighter EV Batteries
Performance and safety are critical when it comes to electric vehicle batteries, and plastics are making that possible.
October 11, 2024
At a Glance
- Composites are key lightweighting solution
- Batteries also need cooling in order to perform efficiently and safely
- FabBatt, the newest addition to ADM Montréal and Expoplast, will highlight innovations in battery technology
Editor’s note: Innovations in battery manufacturing and material production will be a hot topic at FabBatt, the newest addition to Advanced Design & Manufacturing Expo (ADM) coming to Montréal’s Palais des congrès on Nov. 13 and 14, 2024. A full-day conference will address the challenges and opportunities of battery technologies, while suppliers will exhibit related products and services on the show floor. ADM also includes co-locates EXPOPLAST, automation show ATX, D&M devoted to design and manufacturing, PackEx, and Powder & Bulk Solids. As a prelude to the conversations that will take place in Montréal next month, Stephen Moore has drafted this overview of the role that plastics are playing in making EV batteries and components lighter and safer.
Performance and safety are critical when it comes to electric vehicle (EV) batteries, and plastics are playing a pivotal role in delivering on these requirements. Their contribution can be summarized across three key areas — lightweighting, crash resistance, and thermal management.
It’s well known that one of the first questions a potential EV buyer asks is: “How far can I drive this car?” The typical EV weighs in anywhere between 600 and 1,100 pounds heavier than its internal combustion engine (ICE) counterpart, so any means of pulling weight out of an electric drivetrain is high on a carmaker’s agenda. This is particularly so given that batteries are tending to get bigger, if anything.
Taking on aluminum and steel
While aluminum is the current material of choice for battery enclosures, as it is 50% lighter than steel, it is heavier than many plastic alternatives and inferior in terms of resistance to extreme heat — it melts at 630°C (1,220°F) — compared to both steel and fire-retardant polymers. Plastics suppliers are right in assuming their offerings can present viable solutions for both reduced mass and improved safety in batteries. Polyphenylene ether (PPE), polyamide (PA), and other polymers are under consideration for battery housings, offering weight savings of up to 35% versus aluminum
Polyurethane is another material being promoted as a flame-retardant option for battery housings by Covestro and a Chinese Tier I EV maker. The glass-fiber composite material is processed via spray transfer molding.
Polyurethane composite represents a flame-retardant alternative enclosure material for EV batteries. Image courtesy of Covestro.
Glass-fiber composites are also being trialed by Germany’s E-Works Mobility in a project with SGL Carbon to develop battery covers for commercial EVs. Replacing an aluminum construction, the battery housing offers considerable weight savings, but also better battery insulation and fire protection thanks to the significantly lower heat conduction compared to aluminum or even steel.
As performance heats up, batteries need cooling
Battery cooling is an essential component of design for reasons of both safety and performance, particularly for high-performance EVs where liquid cooling using a water/glycol mixture is common. In one such vehicle, a hypercar from RML Group, BASF supported development of a cooling system based on PA 6 pipes (pictured above as the feature image). PA was also used in the battery housing and individual battery cell holders.
Japan’s Asahi Kasei has also developed an innovative solution for battery cell holders that obviates the need for potting, a process whereby the gaps between the cells and the cell holders are filled with a compound based on materials such as polyurethane and silicone. Without the need for these potting materials, batteries are lighter and — importantly in a world where lithium resources are limited — easier to recycle.
Thermal runaway getting nowhere fast
In the event of a severe accident, a major concern is that the battery, with its highly reactive lithium content, will catch fire. In such cases, prevention of thermal runaway is critical, and plastics are far superior to aluminum in terms of damage limitation.
Cylindrical battery cells arranged within a thermal runaway barrier made of Sabic’s flame retardant Stamax resin with a minimum intercellular gap of 1.0 mm, before thermal runaway test. Image courtesy of Sabic.
One solution being touted as a game changer is long-glass-fiber polypropylene resin from Sabic. The Stamax grade in question reportedly provides the necessary thermal insulation and flame resistance to reduce the chances of cell-to-cell propagation in a thermal runaway scenario and, thus, mitigate the risks of a catastrophic safety incident.
Proving the inherent safety of plastics solutions for EV batteries is challenging, costly and time consuming. To this end, Germany’s Federal Ministry for Economic Affairs and Climate Action is funding Project SiKuBa to simulate thermal runaway in EV batteries and facilitate increased take-up of plastics in battery enclosures.
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