Battery engineers face the daunting problem of maximizing thermal runaway safety whereas optimizing automobile efficiency. This activity turns into much more crucial as cell-to-pack and cell-to-chassis designs improve in recognition as a result of producers lose the added safety that may be constructed right into a module-based design. Though newer chemistries reminiscent of LFP and solid-state are marketed as safer options to NMC, there may be nonetheless a danger of thermal propagation.
Security is a major hurdle that automotive producers should overcome to encourage the widespread adoption of battery electrical automobiles. China (GB38031) and the United Nations (ECE/TRANS/180/Add.20) have set the present benchmark for controlling thermal propagation with their 5-minute delay laws. With higher-range and higher-powered battery packs on the close to horizon, OEMs ought to put together themselves for subsequent laws that can probably get longer (e.g., 10, 20, 30-minutes) till finally, dependable non-propagating methods can be required.
There are a number of pathways for warmth to switch from a cell in thermal runaway to its neighbors. The obvious is cell-to-cell conduction. Different parts to contemplate when creating a thermal propagation mitigation technique embody gasoline administration, secondary conductive pathways (inactive cooling plate, bus bar, and many others.), and energetic cooling (if the mechanism continues to be purposeful after a crash state of affairs.) Cell-to-cell boundaries are the primary line of protection when attempting to regulate thermal propagation.
Cell-to-Cell Limitations Should Handle Mechanical and Thermal Vitality
In pouch and prismatic cell functions, a cell-to-cell barrier performs two roles:
Cell-to-cell boundaries should act as a compression pad and take up the motion of the cells as they swell with age, in addition to throughout cost and discharge cycles. Throughout these cycles, cells broaden and contract like lungs drawing and expelling breath. Traditionally, this function is crammed by polyurethane foams or silicone foams, however their max publicity temperatures peak at about 100 to 300°C. They’re higher than nothing, however will often not meet 5-minute delay laws.
The second job cell-to-cell boundaries fulfill is a hearth barrier. They have to present distinctive thermal resistance – whereas compressed – at temperatures of 1000°C or larger. Supplies reminiscent of metals and mica sheets carry out properly thermally however are restricted relating to absorbing mechanical vitality.
Aerogel is likely one of the few supplies that may carry out properly in each classes. For many years, aerogel was famend for being the world’s lightest strong and highest performing insulator however was difficult to make at scale and too fragile for sensible functions. Aspen Aerogels partnered with NASA to develop and commercialize the primary versatile aerogel blanket. After greater than 20 years of confirmed success as thermal insulation, acoustic insulation, and passive fireplace safety in industrial functions, Aspen engineered PyroThin, an ultrathin, light-weight thermal barrier for EV functions. PyroThin thermal boundaries can carry out the mechanical perform of a compression pad and thermal function of a fireplace barrier.
World automotive OEMs select PyroThin as a part of their thermal propagation mitigation technique as a result of PyroThin…
Withstands Temperatures as much as 1400°C
Aspen Aerogels developed PyroThin with the understanding that there isn’t a one-size-fits-all answer for cell-to-cell barrier. Totally different cell chemistries burn at numerous temperatures, and so they burn sizzling. PyroThin thermal boundaries are a tunable platform the place the aerogel chemistry and fiber reinforcement will be adjusted for an utility’s necessities.
Acts as a Springy and Resilient Compression Pad
PyroThin harnesses silica aerogel’s engineered nanoporosity to ship class-leading thermal and mechanical efficiency in a light-weight format. Through the aerogel curing course of, lengthy silica-polymer chains are shaped, and so they act collectively as billions of elastic nano-springs. A versatile aerogel blanket has pores which are 10,000x smaller than some other insulation materials. At this magnitude, the physics fully change. PyroThin has a thermal conductivity decrease than nonetheless air, so when it’s compressed, the thermal conductivity truly improves.
Thermal Resistance, Even When Compressed
Aerogel has the bottom thermal conductivity of any materials on Earth. In contrast to conventional insulations, aerogel doesn’t depend on trapped air. When PyroThin is compressed, the air which has a decrease or worse thermal conductivity than aerogel is squeezed out. This implies thinner cell-to-cell boundaries, extra cells inside modules, lighter packs, and elevated vary.
PyroThin Superior Thermal Limitations Present Promise for a Non-Propagating Future
Along with automotive OEMs subjecting PyroThin to real-world testing, Aspen Aerogels has developed a sequence of mini-module assessments. Two cells – a set off cell and an adjoining cell – have a PyroThin thermal barrier between them to see if it will possibly stop thermal propagation from one cell to the opposite.
Within the take a look at setup above, two 62 Ah prismatic cells (CATL) are compressed inside a jig to take care of cell face stress. Aspen designs thermal propagation assessments for finish of life (EOL) pressures, so the two.35mm PyroThin was at about 50% pressure. A 160W heating pad triggers the cell into thermal runaway.
Apparently, when the cell vents, the stress drops, and PyroThin can barely broaden between the cells. Over the course of half-hour, the adjoining cell reaches a peak temperature of 130°C on the 5-minute mark however doesn’t go into thermal runaway. It is very important word that this mini-module configuration isolates the conductive pathways from secondary pathways in an precise pack configuration. Nonetheless, this testing showcases that thermal runaway will be stopped on the cell-to-cell stage. Engineers can now shift their consideration to the opposite mechanisms and learn how to isolate them, finally working their method in direction of a non-propagating design.
PyroThin thermal boundaries are a confirmed answer, each in laboratory settings and on the highway. Aspen Aerogels was named an Overdrive Award Winner for Launch Excellence, as a part of Common Motors’ thirtieth Provider of the Yr Award. PyroThin’s expertise and Aspen’s agile engineering assist performed an important function in GM’s thermal propagation technique for his or her Ultium battery platform.
To be taught extra about PyroThin thermal boundaries, go to Aspen Aerogels’ web site to talk about your thermal propagation challenges with Aspen’s technical group. Or register for Aspen’s upcoming webinar – Superior Thermal Limitations: The best way to Remodel Your Thermal Runaway Mitigation Technique