E-Mobility Engineering 015 l EMotive Scarab off-road truck dossier l In Conversation: Giulio Ornella l Hall effect and magnetic sensors focus l Challenge of batteries for heavy-duty EVs l Alpha Motor Corporation digest l Automated charging insight l HVAC systems focus

energy densities at both the cell and system levels, they enable higher payloads and therefore more cost- efficient use of the entire vehicle.” Pierre Blanc, chief technology and industrial officer at Leclanche, concurs, adding, “Graphite anode cells are best suited for battery-electric vehicles, and are typically used with an oxide cathode such as NMC or NCA, or with an olivine structure such as LFP. “NMC has the advantage of higher energy density – typically 30% higher than comparable LFP cells – whereas LFP might have the advantage of reduced dependency on some critical metals. Since both technologies tend to use a graphite anode, the initial safety concerns are very similar, such as the kinds of reactions that initiate on the anode, or the potential for burning the electrolyte, with cathode contributions only occurring later in the thermal runaway process.” Dr Martin Busche, VP of r&d for Akasol, adds that silicon-carbon composite anode chemistries can be ideal for enhancing the energy densities and charging speeds of NMC batteries. However, he cautions on the costs of these materials, noting that the supply chain instabilities and price fluctuations of nickel, manganese and cobalt in particular can present financial risks. “Current geopolitical events pose a multitude of risks for mined materials such as cobalt,” he says. “Furthermore, raw material price increases and a 600-660 V supply, although the company is working on 800 V buses for its future solutions. A typical commercial vehicle pack measures 1700 to 2000 mm in length, is 700 to 900 mm wide and 300 mm in height, and charges at between 0.9 and 3.0 C. In terms of enclosure ruggedness, Leclanche’s executive VP for eTransport Phil Broad comments, “IP67 is the most realistic rating that will be required. The batteries will be operating at voltages close to 1000 V, and at those levels the isolation of the single components from the grounding is extremely important. “Also, any humidity – be it from condensation or water ingress – or foreign particles that might enter the battery enclosure could reduce the isolation value, and that could lead to safety issues, with the potential of arcing happening in the battery.” Cell considerations With these pack specifications in mind, the question arises of how the battery manufacturers achieve them. Many will anticipate (correctly) that the creation of the ideal battery pack starts at the cell level: pack suppliers nowadays have a wealth of cell materials and configurations to choose from, so there is much to consider when settling on the optimal cell type. Right now, one of the most pressing questions among battery manufacturers is whether to continue using lithium nickel manganese cobalt oxide (NMC) cells or to switch to lithium iron phosphate (LFP) as the cathode material. Dr Beckmann comments, “In terms of total cost of ownership, LFP might seem like the logical choice at first glance. However, trucks and buses have to take into account that the maximum vehicle payload is reduced by increases in the weight of the battery system. As nickel-rich NMC – and NCA [lithium nickel cobalt aluminium oxide] – chemistries offer higher gravimetric upcoming shortages in nickel, manganese, graphite and so on will severely exaggerate supply gaps and price risks throughout the supply chain. LFP is a little less affected, but it is not a 1:1 replacement for NMC-based chemistries. “Certainly, LFP offers cost benefits and the possibilities of bigger cells and lower labour-intensiveness in pack integrations, as it is inherently safer. However, it suffers from lower specific and volumetric energy density than NMC, and – at least from an active material perspective – lower electronic and lithium ionic conductivity, which contribute to lower performance.” Within these electrolyte families, companies must also consider which are the best specific combinations of cathode and anode materials for their application. As Dr Beckmann says, “Nickel content on the cathode side is the most obvious lever for energy density, whereas silicon content on the anode side is the most obvious one for fast- charging capability. “However, maximising these performance points means compromising on cycle life and therefore total cost of ownership. Moreover, the chosen cell chemistry has to be in harmony with other, often overlooked, factors in cell design to strike the perfect balance for heavy-duty applications. “The interplay between cell chemistry and cell form factor is key. Cylindrical cells enable the highest nickel contents and accordingly energy densities while maintaining the highest safety standards. Moreover, they allow the highest flexibility for modular systems and their use of installation space. “On the other hand, the use of big prismatic cells is essential for competitive LFP batteries, thus limiting their application to large packs with limited flexibility. Finally, pouch cells are very cost-competitive at the cell level but require more complex system integration.” ChallengeOf | Batteries for heavy-duty EVs Cylindrical cells often have overpressure current interrupt devices, rupture valves and other safety features that could make them highly desirable for heavy-duty EVs (Courtesy of Akasol) 46 Autumn 2022 | E-Mobility Engineering