Battery engineers face the daunting problem of maximizing thermal runaway safety whereas optimizing automobile efficiency. This process turns into much more vital as cell-to-pack and cell-to-chassis designs enhance 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’s 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 may seemingly get longer (e.g., 10, 20, 30-minutes) till finally, dependable non-propagating programs will likely 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 components to think about when creating a thermal propagation mitigation technique embrace fuel administration, secondary conductive pathways (inactive cooling plate, bus bar, and so forth.), and lively cooling (if the mechanism remains to be practical after a crash situation.) Cell-to-cell boundaries are the primary line of protection when making an attempt to regulate thermal propagation.
Cell-to-Cell Obstacles Should Handle Mechanical and Thermal Power
In pouch and prismatic cell functions, a cell-to-cell barrier performs two roles:
Mechanical
Cell-to-cell boundaries should act as a compression pad and take in the motion of the cells as they swell with age, in addition to throughout cost and discharge cycles. Throughout these cycles, cells develop and contract like lungs drawing and expelling breath. Traditionally, this position 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.
Thermal
The second job cell-to-cell boundaries fulfill is a fireplace barrier. They need 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 in the case of absorbing mechanical vitality.
Aerogel is among the few supplies that may carry out properly in each classes. For many years, aerogel was famend for being the world’s lightest stable 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 hearth 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 position of a hearth barrier.
International 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 any one-size-fits-all resolution for cell-to-cell barrier. Completely different cell chemistries burn at numerous temperatures, and so they burn scorching. PyroThin thermal boundaries are a tunable platform the place the aerogel chemistry and fiber reinforcement could be adjusted for an software’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. Throughout the aerogel curing course of, lengthy silica-polymer chains are fashioned, and so they act collectively as billions of elastic nano-springs. A versatile aerogel blanket has pores which are 10,000x smaller than another insulation materials. At this magnitude, the physics utterly change. PyroThin has a thermal conductivity decrease than nonetheless air, so when it’s compressed, the thermal conductivity really improves.
Thermal Resistance, Even When Compressed
Aerogel has the bottom thermal conductivity of any materials on Earth. Not like 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 Obstacles 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 exams. Two cells – a set off cell and an adjoining cell – have a PyroThin thermal barrier between them to see if it may 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 strain. Aspen designs thermal propagation exams 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 strain drops, and PyroThin can barely develop 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. You will need to be aware that this mini-module configuration isolates the conductive pathways from secondary pathways in an precise pack configuration. Nonetheless, this testing showcases that thermal runaway could be stopped on the cell-to-cell degree. Engineers can now shift their consideration to the opposite mechanisms and methods to isolate them, finally working their approach in direction of a non-propagating design.
PyroThin thermal boundaries are a confirmed resolution, 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 help performed a vital position in GM’s thermal propagation technique for his or her Ultium battery platform.
To study extra about PyroThin thermal boundaries, go to Aspen Aerogels’ web site to talk about your thermal propagation challenges with Aspen’s technical crew. Or register for Aspen’s upcoming webinar – Superior Thermal Obstacles: The way to Rework Your Thermal Runaway Mitigation Technique
