Tesla Battery Day: Leading the Charge in Battery Innovation

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IT WAS widely expected that Elon Musk, CEO of electric car company Tesla, would announce the development of a million-mile battery at the recent Tesla Battery Day event on 22 September. While that headline-grabbing announcement didn’t quite materialise, in many ways the innovations across all of battery chemistry, cell design, and manufacturing methods amounted to something even more impressive. The announcements of an overall 54% increase in range was hugely exciting but it was coupled with some amazing innovations in Tesla’s chemistry and manufacturing methods to achieve huge reductions in manufacturing costs and increases in efficiency.

The overwhelming impression from the event was that the company is innovating at every level of the supply, design and manufacture of batteries from mining of the metal ores right through to how the batteries are installed in its vehicles. The Tesla CEO set out some hugely ambitious projects, including new battery architecture, more efficient higher capacity factories, and new ways of incorporating battery packs into vehicles that could be transformative in electric vehicle design, and are clearly aimed at reaching his stated goal of a US$25,000 production vehicle within three years.

Cell chemistry

From a chemistry point of view, the announcements about some of the more basic aspects of cell chemistry were enticing, particularly given their general applicability outside of the EV field in the battery industry as a whole. Prominent among these was Musk’s announcement of new electrode technology both at the anode and cathode parts of the battery.

It had been rumoured that Musk might announce new developments based on the incorporation of silicon nanowire in anode structures and, while he did show up on stage wearing a t-shirt bearing a picture of what seemed to be nanowires, the announcement was in fact more fundamental. If the event is to be believed, it seems that the Tesla engineers might have solved many of the problems surrounding volume expansion when using silicon as an electrode material. The announcement was light on detail but they suggested going right back to silicon powder and forming an elastic protective coating around the particles, followed by embedding those into a robust binder. While this encapsulation approach has been proposed before, when more details emerge it will be interesting to see how far down the path to a commercial battery the Tesla engineers have managed to progress. The claim is that this provides a gateway to an anode material that is alone responsible for a huge 20% increase in the range of Tesla’s electric vehicles.

The second announcement about basic cell chemistry was even more vague in terms of technical detail. In their discussions of new cathode technology that removes the need for cobalt, the Tesla team just referred to “novel coatings and dopants” to achieve this. Despite the longstanding industry desire to reduce or eliminate reliance on cobalt in batteries due to high cost and concerns surrounding the ethics of the mining operations in the Democratic Republic of Congo, many will be waiting for full technical details before ticking that particular problem off the list.

Manufacturing

From an engineering and manufacturing perspective, the two big innovation announcements came in the form of the “tabless” cell technology and solid state electrode coating methods. The former had been predicted from a Tesla patent application earlier this year – the main idea being to remove the standard electrode “tabs” connecting the “swiss roll” electrode sandwich structure to the battery terminals. This significantly reduces the length of the electrical path between the electrode and the terminal, so significantly reducing the resistive heating problems that typically hinder the formation of larger cells. In addition, the manufacturing of the electrode “swiss roll” is much simpler because, as Musk noted, the machinery doesn’t need to keep stopping for the tabs.

Tesla’s purchase of Maxwell Technologies in 2019 was the basis for the announcement of the second innovation in battery manufacture. Although it was clear that some final development work is still needed to reach a production-scale battery, the engineering team have apparently developed the lab-scale dry electrode coating technology up to a pilot-plant scale. The removal of solvents from the electrode coating process massively reduces the complexity of the manufacturing and allows Tesla to reduce both the factory footprint and the energy cost per KWh of battery capacity.

Overall, the improvements in manufacturing methods apparently give Tesla a factor of ten times reduction in both factory footprint and energy requirements for a given battery capacity. The result is a headline-grabbing 75% reduction in capital investment per GWh of battery capacity, a 7x increase in KWh capacity output per production line and a huge 10x reduction in overall factory footprint. This means that where the huge “Gigafactory” in Nevada can produce 150 GWh/y of battery packs, these new developments would enable the slightly smaller factory footprint to site a “Terafactory” producing a predicted 1 TWh/y of battery capacity.

Good news: and not just for Tesla

While the broad brush nature of the Battery Day event naturally highlighted the headline improvements, many of these developments have been proposed in principle before, so the industry will be waiting with interest to see the technical details of how the Tesla team have made inroads into the problems.

It was also notable that given all the talk of increases in battery chemistry and manufacturing capacity, there was little discussion of the control systems that will be needed to charge and discharge these more powerful batteries and to meet the customer demand for shorter charge times. However, given the all-encompassing nature of Tesla’s approach to innovation at every stage of the battery development and deployment, it would be naïve to think that it is not also putting significant resources into that area as well.

While these developments in battery chemistry are clearly good news for Tesla and its drive to squeeze greater range into its vehicles, given its open source philosophy in relation to patents, it could also provide an immediate injection of this valuable technology into other battery markets.