E-Mobility Engineering 017 l ECE Doosan electric excavators dossier l In Conversation: Matt Faulks l Battery testing focus l Battery Show North America 2022 report l Ariel Hipercar digest l Cathode materials insight l Thermal management focus

striving to find one-fits-all solutions and ideally a single thermal management fluid. “Dielectric thermal management fluids might open up novel thermal management options for the vehicle manufacturers,” the fluid specialist notes. In the best case, developing enabling technologies such as thermal interface materials, gap fillers and adhesives should run ahead of mechanical design concepts so that dedicated thermal management solutions can be integrated optimally, the expert in these materials says. “The target should be to have smart, high-performance, cost-efficient solutions engineered in from the start, rather than having to solve a thermal problem at the end of the design path,” he explains. “Battery pack designers, engineers and manufacturing teams should involve thermal management suppliers at the pack design stage to ensure that the right materials are selected, and that manufacturing feasibility is considered,” the second materials specialist adds. Runaway prevention Preventing or mitigating thermal runaway is, naturally, a vital part of thermal management, and the materials and technologies that contribute to this are developing rapidly. “The most important improvement we have seen in this respect is the emergence of lithium iron phosphate [LFP] battery chemistry for mainstream EVs,” the fluids specialist says. “LFP battery chemistry is inherently safer than the nickel manganese cobalt-based chemistries that are dominant these days, owing to its higher chemical and thermal stability. “However, although it costs less, LFP hasn’t often been used because of concerns about its lower energy density, leading to lower ranges, but these have been addressed through cell-to-pack engineering. As such, we have seen major European EV manufacturers start to move towards the use of LFP for some of their models.” He also highlights the importance of the latest battery management systems to safety, emphasising that they have improved dramatically since the first modern EVs emerged, and can now safeguard the pack from conditions that could cause thermal runaway. “They can also implement mitigation strategies when a thermal event is detected, such as activating the thermal management or electrically isolating the damaged cell,” he says. “Combining that with an immersion cooling system can offer even further improvements owing to the improved heat transfer. “Advanced electrolyte engineering will increase the temperature required to enter thermal runaway compared with current electrolytes. That will become very important as battery energy density increases.” The electrification specialist’s expert emphasises the importance of managing heat conduction, particularly by controlling its direction in a thermal event. “While cold plates are efficient during normal operations, they have the drawback of providing a conductive path for heat during thermal runaway,” he notes. “An intelligent design approach that limits lateral conduction can slow down the progression of thermal runaway between cells.” In addition to the long-anticipated shift to solid-state cells, the thermal interface materials, gap fillers and adhesives specialist says there are products available or under development that can be applied at the battery pack level for propagation prevention in a thermal event. These include hybrid and multi-functional materials that combine resistance to high temperatures with thermal isolation in lid coatings, cell pads, compression pads and potting foam products. “Depending on the cell type and the overall battery pack design, these products are combined into solutions to help protect passengers and to contribute to the required evacuation times,” he says. An aerogel blanket manufacturer notes that cell-to-cell (C2C) barriers made from these materials have gained popularity for delaying thermal propagation in battery packs containing pouch or prismatic cells. “Aerogel-based C2C barriers can act as both a compression pad and a firewall between adjacent cells. Accomplishing this in the slimmest package possible is critical to meeting energy density and range targets. As the world’s most efficient insulation material, aerogels are uniquely well-suited to this safety-critical application,” an expert from the company explains. Aerogels are solids with the lowest known thermal conductivity. Thermally conductive adhesive that bonds cells directly to the cooling plate is increasingly important as battery designers explore cell-to-pack architectures (Courtesy of Henkel) 66 January/February 2023 | E-Mobility Engineering