The hybrid battery combines the best of two worlds: The advantages of the Li-ion battery and those of the supercapacitor. However, it is currently only suitable for niche applications in the on-highway sector.
Superbattery by Skeleton Technologies
Skeleton Technologies
Hybrid batteries combine the energy storage of a capacitor and a battery in one system or module. The advantage: They release large amounts of energy slowly and continuously while at the same time meeting high peak power requirements. At present, however, the possible applications in the automotive sector appear to be limited.
Generally speaking, when designing battery systems, "a balance between a high energy content and a high power output" must be struck, as Richard Backhaus writes in the article Hybrid Batteries – The Best of Two Worlds from MTZworldwide 9-2024. "For applications with short and extremely high power peaks, this is in most cases very difficult to achieve. One solution is a combination of a battery and a supercapacitor. This concept provides support for the battery during power peaks and makes the energy supply process more dynamic," says Backhaus.
According to Backhaus, there are several options for constructing the hybrid battery. On the one hand, the battery and supercapacitor can be constructed as discrete components and connected together. This would offer the possibility of actively regulating the energy flows. Secondly, the battery and capacitor functions could be combined in a single component. The German-Estonian energy storage specialist Skeleton Technologies "has pioneered this technology and is marketing the combined battery and capacitor cell under the name of Superbattery", explains Backhaus.
Skeleton's Superbattery
With the so-called Superbattery, Skeleton combines "the storage mechanisms of lithium-ion batteries and supercapacitors within the battery cell. Specifically, that means combining the capacitive storage portion of the supercapacitors with the intercalation-based storage of lithium-ion batteries", as Dr. Linus Froböse, Chief Technology Officer and Managing Director at Skeleton Technologies, explains in the interview “We do not see the Superbattery in direct competition with the lithium-ion battery” from MTZworldwide 6-2024.
According to Froböse, it is crucial that both components are brought into close contact with each other so that they function together as a unit. The Superbattery is constructed like a conventional battery cell, but the company's expertise lies in the anode. "It combines materials for capacitive energy storage (Curved Graphene for the supercapacitor function) and intercalation (the battery function)," explains Backhaus.
For Skeleton, superbatteries are a complement to supercapacitors and conventional lithium-ion batteries. One of the main growth areas for ultracapacitors is the hybridization of battery and ultracapacitor to pave the way for smaller, longer-lasting and more powerful battery systems. According to Backhaus, the first generation of Skeleton's Superbattery is set to go into series production at the end of 2024. "It offers a high power density of 4 kW/kg, an energy density of 65 Wh/kg, a lifetime of 50,000 charging cycles and a fast charging time of only 60 s for the battery. Industrial production of the second and third generations of the product is planned for the end of 2027 and the company is promising lower costs as a result of economies of scale, together with double the storage capacity for the battery cell", explains Backhaus.
Applications for the Hybrid Battery
Use cases are applications where a lot of power is available and required for a short period of time. "Examples include actuators for automated driving and electrically heated catalytic converters that have to be brought up to operating temperature quickly during cold starts," says Backhaus. In the field of electric powertrains, there is an opportunity of electrification in niche applications such as mining trucks, machines or municipal supply vehicles. On the other hand, the hybrid battery concept is less suitable as a traction battery for electric and plug-in cars. Some companies, such as FEV, are more critical of hybrid battery technology. The development service provider therefore sees the hybrid battery "in niche applications such as racing cars or special 48 V systems, because of their higher cycling stability and lower temperatures", writes Backhaus. In the mass market segment, the focus is still on energy content.
It can be stated: "The advantages that hybrid batteries have over existing lithium-ion cells primarily relate to their power density and, to a lesser extent, their cycling stability, thermal management and safety. By contrast, the disadvantages include the maturity, energy density and self-discharge rate.," says Backhaus. The current trend towards fast charging of battery systems could have a positive effect on the future development of hybrid batteries. According to FEV, the use of solid electrolytes in lithium-ion capacitors would be a technical challenge.
This is a partly automated translation of this German article.
