What is it about miracle batteries
Reach or Castle in the Air?
CATL sodium battery
© press-inform – the press office
Electromobility craves range. New battery types promise a remedy. Together with the battery expert Professor Maximilian Fichtner, we’re examining four of the most important technologies and clarifying how likely it is that they’re ready for series production.
Hardly a week goes by without new Wunder batteries being introduced that promise a range of more than 1,000 kilometers and can be charged at lightning speed. In most cases, it should only take ten minutes for the energy cells to be filled up to 80 percent. These values are conspicuously based on those of a diesel car. The new and revolutionary batteries are often promised to be implemented very quickly, before you often hear nothing more after a while. Anyone remember NanoFlowCell? The decisive breakthrough has not yet been achieved. That just goes to show that the Prussians aren’t shooting that fast when it comes to electrochemistry either. The path from an idea to a small series to series production in automobiles is a lengthy one. The demands on the batteries in a car are significantly higher than on batteries for entertainment electronics. It’s about service life, safety, performance and, of course, costs. If a component is produced several hundred thousand times, the cent amounts increase exponentially. The hottest irons in the range fire are Tesla researcher Jeff Dahn’s two-million-mile battery pack, the SALD batteries, the sodium-ion batteries, and of course the solid-state batteries. “In my view, these are not “miracle batteries” but technical developments that promise technical progress here and there,” explains Maximilian Fichtner, Professor of Solid Chemistry.
If you apply these standards, the field of promising miracle batteries thins out quickly. Tesla battery researcher Jeff Dahn recently gave an interim report on his work at an online conference hosted by battery software analysis company Twaice. The goal is still to design a battery that lasts 1.6 million kilometers without losing any significant performance. The US researcher had already presented a new cell in October 2020 that can handle around 10,000 charging cycles. For an e-car with a range of 350 kilometers, this would correspond to a mileage of more than three million kilometers. Current electric cars manage 1,500 to 2,500 charging cycles and then still have around 70 to 80 percent of their original capacity. Another advantage of these Marathon batteries is that they can easily be used as energy storage and, with intelligent networking, can solve charging and energy problems. Maximilian Fichtner brings light into the American darkness. “Jeff Dahn’s previous developments went in the direction of producing the powder particles of the storage material as perfect crystal particles, which are less susceptible to attack by the electrolyte. This means they last significantly longer. In addition, he is in the process of making small, targeted changes to the material composition to further stabilize it I think that’s quite feasible and Tesla’s previous materials also show that it’s possible in principle.”
The SALD (“Spatial Atomic Layer Deposition”) is a concept that aims to take batteries to a new level. However, this is not a revolutionary type of battery, but an improvement in the components. So this is an evolution of lithium-ion batteries, in which the cells are coated with an ultra-thin atomic coating, which significantly facilitates the flow of ions between the anode and cathode, thus improving safety and longevity significantly faster charging. Maximilian Fichtner is skeptical: “I think this is a technical solution that may make sense for small batteries, since the costs are not so important there. I can’t imagine such batteries in the automotive sector.”
With faster charging times, higher energy density and more power, the solid cell battery offers similar advantages to the SALD process. It is assumed that these batteries will come. Because the charge is no longer transported by a liquid but by a solid electrolyte and by replacing the negative pole, which previously consisted of graphite, with pure, metallic lithium, the batteries could become lighter and, according to Maximilian Fichtner, about 30 to 40 percent more bring range. So far so good. However, with the previous lithium-ion batteries, small metal needles gradually form on the lithium during charging and discharging, which in the worst case can lead to a short circuit in the battery. To prevent this, the solid-state battery replaces the liquid electrolyte between the electrodes with a thin ceramic layer. It is not flammable, but conducts the lithium ions and also forms a mechanical barrier for the metal needles (dendrites) mentioned. “The difficulty is to manufacture it in such a way that the arrangement is stable over a long period of time and the many small contact surfaces of the different solid bodies do not tear off during loading and unloading,” says Maximilian Fichtner, outlining the problem.
BMW, Mercedes and VW are investing billions in this new technology. The Chinese carmaker Nio has also announced a solid-state battery and long ranges for its ET7 electric sedan, which is due to be launched this year. The ADAC even speaks of a “world sensation”, but admits that the top model with the new batteries will not be available at dealers until 2024. With other manufacturers, the solid cells will not appear overnight in the series models. Mercedes has been working on these cells for a long time, but has realized that things are not progressing as quickly as originally thought. There is still a little work to be done, especially with regard to energy density and charging speed. BMW apparently shares this assessment and intends to bring the first production car with solid cell batteries onto the market by the end of the decade. First of all, the solid cell batteries are used in buses.
The Chinese battery cell producer CATL (Contemporary Amperex Technology) announced a sodium-ion battery for the year 2023 last year. The advantages of the rechargeable batteries, which do not require lithium, nickel and cobalt, are not only the costs and sustainability, but also the thermal stability at sub-zero temperatures and the ability to charge quickly. For Maximilian Fichtner, these batteries are one of the “most exciting new developments at the moment. Here you have the perspective of building very powerful batteries on a sustainable material basis. I think the system will have a great future and it can bring great relief to the tense raw material situation in the Li market. A few years ago this was dismissed as a gimmick and something exotic. The cells are now ready for the market.” On the minus side is the comparatively low energy density, but something is already happening in this area. According to Chinese media, CATL filed a patent earlier this year that increases the energy density of sodium-ion batteries by 25 percent to 200 Wh/kg. For comparison: The top cells from the VW Group are currently just under 300 Wh/kg.