E-Mobility Engineering 014 l InoBat Auto dossier l In Conversation: Brandon Fisher l Battery monitoring focus l Supercapacitor applications insight l Green-G ecarry digest l Lithium-sulphur batteries insight l Cell-to-pack batteries focus

Each of the four target segments is considering different form factors and different chemistries, he adds. For high- performance automotive and aviation, the latter is highly weight-sensitive, while the commercial and off-highway segments are showing interest in large- format cylindrical and prismatic cells. “Some of the segments we are looking at want to go and explore, and they can now do that because we are willing to talk to them,” MacAndrew says. There is also growing interest in cells suited to cell-to-pack and cell-to- chassis battery construction, he notes. “This has driven some really detailed analysis to assess not only how the cell cost plays out, but also how the cost and efficiency of integration can be optimised for them,” he explains. “We see a trend towards looking at large-format cylindrical cells with both terminals at one end of the cell or with terminals spaced far enough apart to get high power out of them, and the pack assembly process is somewhat simpler.” At the same time, he adds, prismatic form factors have been shown to allow for cell-to-chassis construction, while pouch cells need more mechanical support. “There is a trend towards looking at how the pouch can be supported, how it can be mounted and maintained, and how all of that can be simplified,” he says. “We see large form factor pouch cells being considered to reduce the number of components in an installation, which provides the opportunity to optimise cost. How that thinking will translate into final decisions about the sizes and types of cells to adopt remains to be seen, but we are in discussion with a number of OEMs who are looking at it.” NMC 622 and 811 InoBat Auto selected NMC chemistries for their energy density, service life and power density-focused products: NMC 622 and NMC 811. While the numbers refer to the proportions between the named elements in the cathode mix – six parts nickel to two parts manganese and two parts cobalt, for example – they are not exact, as both NMC 622 and 811 are labels that refer to families of chemistries. “A 622 could be 65% nickel and still be called a 622,” MacAndrew explains. “We talked with most if not all of the materials providers to give us the chance to assess the efficacy of all their elements and to decide how each of them is best applied as part of our combinatorial approach to developing solutions,” he says. “A 622 would have been considered an exotic NMC a few years ago, when 111 would have been the typical cell chemistry implemented initially,” he notes. “Each materials provider is optimising and creating its own families of formulae, 622 being a family that we have been evaluating for cathode use.” He says InoBat Auto has evaluated most of the 622s available at both industrialisation and pre- industrialisation levels, and reports good results. Measured against cells considered the best in class at the time, these chemistries proved to be just as good as the comparison cells in most parameters, such as gravimetric energy density, while improving on them in key target parameters including lower internal resistance and higher volumetric energy density. InoBat Auto has also continued to evaluate 811 chemistries for cathode use, MacAndrew says, in an effort to improve stability, capability and in particular the life of cells with 811-based cathodes. As with 622 chemistries, 811 formulae are not all the same: a formula with 85-86% nickel would still be called an 811 even with just 0.5% by weight each of manganese and cobalt, he adds. Cell energy density can also be greatly improved by preloading (pre- lithiating) the graphite anode with silicon. “We have been screening silicon materials for some time that will go into cells that already contain our graphite elements – we have anodes with 622 graphite and 811 graphite base chemistries,” MacAndrew says. He classes the 622 and 811 cells with graphite-based anodes as InoBat Auto’s first- and second- generation technologies, while those under development with silicon-based anodes as generations three and four. “We have produced experimental cells with increasing levels of silicon on the anode that deliver energy capacities of around 350 Wh/kg, which we see as a break-over point for automotive, and pushing towards 400 Wh/kg, which we think is the 0no)at (uto oɈers pouch cells (below left), some in larger formats (below right), prismatic cells (bottom left) in diɈerent siaes while cylindrical cells (bottom right) are also attracting interest 24 Summer 2022 | E-Mobility Engineering