Prof. Dr. Dr. Andreas Hintennach is head of battery cell research at Daimler, and he gave an insight into the Group’s development and research goals at a digital roundtable. Daimler assembles the battery packs for its electric cars and purchases the battery cells contained in the core. Hintennach indicated that all phases from basic research to production maturity were covered. This includes the optimization of existing lithium-ion battery systems, the further development of cells and research on new battery systems.
The focus of Daimler battery cell research is currently on the energy storage of the next generations of electric cars after the SUV EQC launched in 2019. Lithium-ion batteries would continue to set the pace in the coming years, but more could be expected. “We are continuously working on innovations and alternatives that go beyond the possibilities of Li-ion batteries – not least in terms of energy density and charging times, but also with a view to sustainability,” said Hintennach.
In addition to energy capacity, security is a crucial factor for Daimler. “A Mercedes-Benz has to be the benchmark when it comes to safety, and that also applies to its battery pack,” said Hintennach. Another guiding principle in the development is flexibility: At Daimler there are numerous applications for battery packs, from smart to Mercedes-Benz cars and vans to buses and heavy trucks – and finally from 48-volt mild hybrids to plug-in Hybrids and pure electric vehicles.
The solutions used by Daimler should also be sustainable, explained Hintennach. Sustainability has become the guiding principle for all development activities for the Swabians. Since the manufacture of vehicles requires a high amount of materials, one of the main focuses of development is on the lowest possible need for natural resources. In addition, the recyclability is taken into account from the start. Battery production would become part of a circular economy.
Cobalt in particular is criticized for the raw materials used in lithium-ion batteries. The metal is repeatedly associated with human rights violations and environmental damage during mining. On the one hand, Daimler relies on the fact that suppliers meet the sustainability requirements of the car group, explained Hintennach. The cobalt share in Daimler batteries of currently less than 20 percent will also be reduced further in the future. The Daimler manager indicated that cobalt could be completely dispensed with later.
Alternatives to lithium-ion batteries
According to Hintennach, cobalt and other materials such as lithium will be followed by materials that are primarily based on manganese – “an ecologically harmless, easy to process raw material”. Manganese already has “excellent recycling” because it has been used in the form of non-rechargeable alkaline batteries for decades. Research must now make this type of battery rechargeable. Daimler assumes that the technology will be ready for the market in the second half of the 2020s.
Another alternative is the lithium-sulfur battery. “Sulfur is an industrial waste product that costs almost nothing, is very pure, and is easy to recycle. It poses great challenges in terms of energy density, but it also has an unbeatable life cycle assessment. However, it may take years before this technology is available for cars, ”said Hintennach. Lithium is also criticized, but this raw material can be replaced. For example, the magnesium-sulfur battery can do without it. The advantage of magnesium is that it is freely available – for example, the whole Swabian Jura is made of lime. At the moment, however, research is still at laboratory level.
Among other things, the solid-state battery is superior to the lithium-ion battery. Several car manufacturers are working on corresponding energy storage systems, and Daimler plans to use them in the Mercedes-Benz eCitaro city bus for the first time from mid-2020. The technology has a very long lifespan, is very safe and also contains no cobalt, nickel or manganese, said Hintennach. However, it is less energy-tight, therefore relatively large and cannot be charged quickly. It is therefore well suited for commercial vehicles, but not yet for cars.
“Whether cells with solid-state electrolytes, lithium metal anodes or lithium sulfur systems – all technologies differ in their specific material requirements, their applications and not least in their degree of maturity,” says Hintennach. Every technology has its advantages and disadvantages. Not yet just around the corner, but not too far away either, are batteries in which the graphite layer of the anode can be replaced by new materials such as lithium metal foils or silicon powder. Both significantly increase the energy density, the result is a greater range and better quick charging.
“Lithium-air batteries actually only contain lithium. The rest – the oxygen – just comes from the air. From a chemical point of view, it’s a concept similar to what we have in the fuel cell, where we use hydrogen. The energy density would be excellent – but this technology is still a long way off, ”added Hintennach.
With the Vision AVTR, Daimler presented a futuristic research vehicle at the beginning of the year. The battery technology is based on organic cell chemistry based on graphene and thus completely eliminates rare, toxic and expensive materials such as metals, explained Hintennach. This would make electromobility independent of fossil resources. The material also allows 100% recyclability through composting. In addition to an exponentially high energy density, the technology also has “exceptional” quick charging capability. Hintennach: “Organic batteries are currently part of our basic research. It will still take several years before they can be introduced in Mercedes-Benz vehicles – but the potential is there! “
For the time being, Daimler will install lithium-ion batteries in its electric cars as before. However, the company is working intensively on improving them as well as new, more powerful battery types. “Our competencies for the technological evaluation of materials and cells as well as the research and development activities are consistently expanded”, emphasized Hintennach.