ADVANCED MATERIALS & PROCESSES | JULY/AUGUST 2023 31 KEEPING EV LITHIUM-ION BATTERIES ‘GREEN’ WITH CT-SCAN DATA ANALYSIS Fire risk in electric vehicle batteries can be reduced by detecting flaws through nondestructive visualization. While the uptick in demand for greener electric vehicles is promising, lingering questions remain about the safety of the lithium- ion batteries they rely upon. Concerns include fires, the risks of electric shock to emergency responders from exposure to high voltage, and the risk of battery reignition. However, fire-related EV accidents may not occur as frequently as headlines seem to suggest. Forbes magazine reports that, in 2022, insurance referral service provider AutoinsuranceEZ analyzed data from the U.S. National Transportation Safety Board (NTSB) and concluded that EVs were actually less prone to catch fire than hybrids or internal combustion engines (ICEs)[1]. But other sources quoted in the article noted that the sample sizes were small and the data insufficient to accurately compare EV safety. Still other sources noted that lithium-ion battery fires are nevertheless more difficult to put out than conventional ones, because the energy release during the exotherm of the electrolyte takes a lot of cooling to extinguish. SCANNING THE DETAILS To address these risks, automotive battery designers are intently focused on understanding the complex chemistry and construction of these increasingly necessary power sources. The same can be said for their manufacturers, who must continuously monitor production processes to ensure that battery cells, packs, and modules adhere to specifications. What is it about lithium-ion batteries that makes them prone to catching fire? Perhaps more relevant to their EV owners is their vehicle’s driving range, time needed to recharge, and long-term battery performance. Each of these must be optimized and any safety risks mitigated before the EV green revolution can reach maximum cruising speed. Industrial computed tomography, more commonly referred to as CT scanning, has begun playing a significant role in answering some of these questions about EV batteries (Fig. 1). So has advanced software that makes sense of CT-generated images, allowing users to measure voids and particle sizes within electrode active material during the research and development phase, detect delamination and contamination during cell manufacturing, analyze electrical connections and electrolyte fill levels, and provide many other quality-assurance functions that were once impractical or even impossible to perform (Fig. 2). BREAKING DOWN THE MANUFACTURING STEPS Three main types of lithium-ion batteries exist—pouch, prismatic, and cylindrical. Whatever the shape, the data from a CT scan of the battery can be analyzed with sophisticated software at any point during its entire lifecycle. This begins with electrode manufacturing, Fig. 1 — Improving traditional and lithium-ion battery safety, longevity, and reliability are possible with advanced CT-data analysis, which quantifies interior material characteristics that reflect chemical states and impact mechanical features such as walls and joints. TECHNICAL SPOTLIGHT
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