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

That is a likely point of divergence between the key markets for InoBat Auto’s cells for high-performance automotive and aerospace applications, as the former is increasingly adopting liquid cooling – with immersion cooling using dielectric fluids on the horizon – while most electric aircraft developers are keen to avoid it because of the extra weight and complexity involved. Duty cycles Wight argues that a deep understanding of the duty cycle ought to play a central role in making such choices. “If you can achieve the duty cycle with air cooling, you take quite a lot of weight and complexity out of the system, and that has obvious benefits in a lot of areas,” he says. He cites a motorsport application involving very high temperatures and aggressive g-forces as an example. “The solution for that was to allow the thermal mass of the battery to control its temperature through a well-known duty cycle, then use forced air cooling between events,” he says. “It was a great solution for that environment. Reliability was key and, as ever, if you have a very harsh environment, the more parts you put into it, the greater the likelihood you’ll have a failure.” Future developments Beyond generations one through four, InoBat Auto has a roadmap for further an important part of the BMS’ job is balancing the cells. It does so by stopping, slowing or accelerating the charging of individual cells using dedicated resistors, and with active charging moving charge between cells to equalise them. “We can help by making our cells as accurate and repeatable as possible to minimise balancing time,” he says. Cooling advice Thermal management is another pack-level task that is generally the responsibility of the battery integrator or the vehicle OEM, with which InoBat Auto, as the cell supplier, can offer help and advice. “Obviously there is an operating window for the cells and, as you increase power and draw high currents, internal resistance will generate heat, and at some point the battery will have to be actively cooled,” MacAndrew notes. “Our approach is to make sure the cell surface can be accessed so that heat can be extracted and dissipated to a cooling system.” While InoBat Auto provides cells that operate safely over a well- defined temperature range, which is communicated clearly to the vehicle OEM, he says, the OEM is faced with the challenge of managing the weight budget and complexity involved in delivering a stable system, part of which involves choosing between air or liquid for the cooling medium. electrochemical development. “That includes more exotic materials for the cathode,” MacAndrew says. “We are also evaluating how we can further optimise the performance of the anode, and we are ultimately looking at combining the functions of the separator and the electrolyte.” The central aim of these efforts is to maximise the gravimetric and volumetric energy densities, which depends to a large extent on how many lithium ions can be packed onto the electrodes. “There is a theoretical maximum for both electrodes that is not possible to achieve, but which we use when we assess how much energy per gram, per square centimetre, we can get into the designs we are developing,” he says. While pre-lithiation of the anode is one way of increasing the number of ions it can hold, using lithium metal for the anode comes as close to the maximum that can be achieved, he explains. In parallel, the company is working on solid-state cell technology, with a focus on safety in general and optimising the separator in particular. “We are carrying this out independently of other activities at this point to assess the functionality we are trying to achieve,” MacAndrew says. “Ultimately, that will allow us to offer solid-state solutions as well, and they might be paired with our lithium anode.” From r&d to gigafactories All of the above relies on the company’s r&d, prototyping, sampling and volume production capabilities that at the moment rely on partners in the Asia-Pacific region but will transfer to Europe over the next 2 years, with director for strategy execution and programme management Pavol Krokos steering the process. Construction is under way on the first facility in Slovakia, with a second, much larger one nearby at the planning stage. In the meantime, sample batteries are already being delivered, Krokos says. “Working closely with our technology partners and contract manufacturing 0no)at (uto is planning its first gigafactory, Volta , which will be fully automated, ne_t to its Volta r d and semi-automated production centre 28 Summer 2022 | E-Mobility Engineering