EV packages are accelerating at an unprecedented tempo as automotive OEMs race to realize their electrification targets. Subsequent-generation battery platforms are fueled by innovation, however this new know-how requires engineers to study on the job whereas concurrently designing their packs. Gaps in understanding a component’s efficiency can result in engineering change requests (ECRs) and delay manufacturing.
Passenger and industrial automobile OEMs in Asia, Europe, and North America accomplice with Aspen Aerogels to unravel thermal runaway propagation challenges. Thermal barrier packages typically expertise ECRs as a result of pack-level thermal propagation habits turns into obvious late within the design cycle. Cell-to-cell boundaries are the best half to change when points with meeting, cell-face strain, and cell efficiency come up. Aspen’s in depth data of aerogel know-how and the complexities of thermal runaway has helped OEMs obtain their security targets and keep tight deadlines.
PyroThin is an aerogel cell barrier that may act each as a thermal barrier and compression pad in a single materials. Understanding the lifetime mechanical efficiency of a cell barrier is essential as a result of it impacts the pack’s security and efficiency. Li-ion pouch and prismatic cells have preferences in regards to the cell-face strain they need to be held, which varies by producer. For instance, some cells need a tight embrace, whereas others choose featherlight contact. Discovering the right stability is essential as a result of mechanical habits influences the state of well being.
Cell-face strain evolves as cells breathe throughout cost and discharge cycles, in addition to swell as they age. Over time, cell boundaries are additionally compressed to a fraction of their unique thickness as they’re squeezed between the shifting cells. Predicting that evolution is essential to understanding end-of-warranty and end-of-life battery efficiency. Incorrectly managing mechanical habits can result in untimely cell degradation, resulting in costly guarantee claims or recollects.
Fatigue biking to check mechanical efficiency doesn’t present a full image. Prescribed displacement permits engineers to manage strain however not pressure, whereas the other is true when setting load parameters. Cell-face strain evolves over time as cells broaden and cell boundaries fatigue. Engineers should additionally think about different elements throughout the pack, corresponding to finish plates, cell-to-end boundaries, and different elastic parts.
Aspen designed a extra reasonable check setup to guage cell barrier lifecycle fatigue. If engineers can’t get hold of fully discharged li-ion cells, a surrogate cell could be made from low-density polyethylene (LDPE). To calculate the cell stiffness, take the cell’s modulus and divide it by the thickness. It will inform the required thickness of LDPE. Different inputs required for this check embody geometry, compressive moduli, beginning-of-life strain, swelling and respiratory percentages, and variety of cycles.
Earlier than testing, create a compression drive deflection (CFD) curve for every pattern and calculate the common. In Aspen’s assessments, 1.7mm PyroThin was positioned onto a metal plate above the LDPE block. PyroThin cell barrier samples underwent 1400 cycles to simulate the end-of-life situation of an NMC cell. A brand new CFD curve was then measured, which included the results of fatigue set. The trail between cycle 1 and 1400 was proven to behave logarithmically, enabling engineers to foretell PyroThin’s evolution as a perform of cycle depend. Having PyroThin’s anticipated thickness provides engineers perception into PyroThin’s anticipated thermal and mechanical efficiency all through the pack’s lifetime.
Aspen Aerogels has a devoted in-house mechanical testing lab that automotive OEMs can make the most of as an extension of their testing capabilities. Contact their technical workforce to study extra about higher predicting the lifetime efficiency of cell boundaries.
