The white powder lies like a heap of dust in a bowl in front of Dr. Andreas Roters. He has a twinkle in his eye because he knows that the micro-fi ne ground material will play a major role in an industry that is among the most promising worldwide. “We are developing a glass-ceramic material that will play a key role in tomorrow’s batteries for electro-mobility,” reveals Dr. Roters. The expert in SCHOTT’s central re- search department is in charge of projects aimed at manufacturing solid-state batteries.
This new battery technology is intended to fulfil long-held wishes of the automotive industry: A range of more than 310 miles for electric vehicles, shorter charging times, higher operational reliability and lower costs. Solid-state batteries show up in the roadmaps of almost all well-known car manufacturers. Toyota announced the first cars with solid-state batteries for demonstration purposes at the 2020 Olympic Games in Japan; Volkswagen and BMW are working with battery experts in this field. According to media reports, the first e-buses from the Daimler brand eCitaro will be equipped with the new technology for driving in urban traffic in the next few years.
What makes the novelty so promising? Solid-state batteries work on the basis of lithium cells, as do the currently prevail- ing lithium-ion batteries. However, in contrast to these, they do not use liquid electrolytes but rather solid electrolytes for ion conduction. In short, this enables the use of alternative electrode materials for anodes and cathodes. In this way, the energy density and storage capacity of the cell can be increased – and thus also the range of electric vehicles. Solid electrolytes are also safer than liquid electrolytes, which escape more easily and ignite. The batteries can withstand higher temperatures and age less quickly. They no longer require overly complex cooling and safety encapsulation, which brings advantages in terms of size and weight. In addition, laboratory tests have shown that shorter charging times can be achieved with solid-state batteries than with lithium-ion batteries.
Glass-ceramic powder is now used at a central point in the battery: as an ion-conducting solid electrolyte. SCHOTT’s team of experts has developed materials with high conductivity as well as defined chemical and temperature stability for this purpose and has demonstrated in two research projects lasting several years that these materials are suitable for use in solid-state battery cell systems. These are two of the most promising material classes for high lithium ion conductivity. The production of one of the materials in a proprietary SCHOTT melting process is unique worldwide.
“Our team is in the process of further developing these materials and their production on an industrial scale to achieve the best possible performance,” says Dr. Roters. For decades, SCHOTT has been manufacturing glass-ceramics using the classic melting process with subsequent ceramization. “This combined process, which is followed by pulverization and, depending on the cell concept, sintering, is not only highly scalable and therefore cost-effective, but also opens up additional degrees of freedom in material design,” says Dr. Roters. “For example, we have already been able to reduce interfacial resistances in order to improve performance. And we’re working on turning our materials into a barrier for dendrites,” he adds. These excesses, which are formed on electrodes by the highly reactive lithium, can cause short-circuits, which so far have prevented the use of high-energy lithium metal as an anode.
SCHOTT researchers are developing harmonious material designs for various cell concepts of solid-state batteries: for purely oxidic systems with sintered materials; for polymer hybrid systems in which plastics are combined with glass- ceramic particles; and in North America also for sulfide systems. “We have been working with solid-state batteries since 2011, when hardly anyone in Europe spoke of them. We are now involved in a variety of cooperation and development projects and have built up a global network of partners with contacts to leading automotive manufacturers and suppliers,” says Dr. Roters. Although sampling is now carried out only on a small scale and demand is increasing, the expert remains realistic: “Materials research isn’t over yet. It will be some time before all the wishes of the automotive industry can be fulfilled.” He is convinced however, that when mass production begins – it will be there, the white powder.