EV packages are accelerating at an unprecedented tempo as automotive OEMs race to attain 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 an element’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 resolve 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 obstacles are the best half to change when points with meeting, cell-face stress, and cell efficiency come up. Aspen’s intensive information 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 stress they need to be held, which varies by producer. For instance, some cells need a tight embrace, whereas others want featherlight contact. Discovering the proper steadiness is vital as a result of mechanical habits influences the state of well being.
Cell-face stress evolves as cells breathe throughout cost and discharge cycles, in addition to swell as they age. Over time, cell obstacles are additionally compressed to a fraction of their unique thickness as they’re squeezed between the transferring cells. Predicting that evolution is necessary 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 stress however not pressure, whereas the alternative is true when setting load parameters. Cell-face stress evolves over time as cells develop and cell obstacles fatigue. Engineers should additionally contemplate different elements inside the pack, comparable to finish plates, cell-to-end obstacles, and different elastic components.
Aspen designed a extra life like check setup to judge cell barrier lifecycle fatigue. If engineers can not acquire utterly discharged li-ion cells, a surrogate cell may 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 embrace geometry, compressive moduli, beginning-of-life stress, swelling and respiratory percentages, and variety of cycles.
Earlier than testing, create a compression power deflection (CFD) curve for every pattern and calculate the common. In Aspen’s exams, 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 offers 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 group to study extra about higher predicting the lifetime efficiency of cell obstacles.
