Recent advances in material technology have led to the development of new types of energy storage devices that greatly surpass conventional lithium-ion batteries in terms of performance. This September, Skeleton Technologies GmbH announced that it is teaming up with the Karlsruhe Institute of Technology (KIT) to develop a “SuperBattery”. Skeleton is a startup based in Estonia, while KIT is one of Germany’s major research and educational institutions. According to the press release from Skeleton, the SuperBattery is designed to be fully charged in just 15 seconds and has a huge potential in the application field of electric vehicles (EV).
This energy storage system is actually a hybrid of an ultracapacitor (or supercapacitor) and a lithium-ion battery. Furthermore, the ultracapacitor will be made with “Curved Graphene”, which is a patented carbon material developed by Skeleton. The startup claims that the hybrid design is highly beneficial for EVs because the battery and the ultracapacitor complement each other by combining their strengths and mitigating the other’s weaknesses.
Lithium-ion batteries are recognized for having a high energy density, which translates to a large storage capacity. However, they are also recognized for having a low power density, which translates to a slow charging speed. Although carmakers have adopted lithium-ion batteries in the development of their electric models, reducing the charging speed has become a bottleneck in addition to building out the charging network.
Ultracapacitors are completely opposite of batteries. Having a very fast charging speed is the main advantage of ultracapacitors, and it derives from the high power density that characterizes this type of device. Unlike lithium-ion batteries or any other kinds of batteries, ultracapacitors store potential energy in an electrostatic field rather than in a chemical form. They therefore can release energy rapidly and in bursts. At the same time, they can be charged up quickly and will remain structurally stable through tens of thousands of charging/discharging cycles. On the other hand, ultracapacitors have a lower energy density. This means that they are larger and heavier than lithium-ion batteries for the same storage capacity.
Due to having opposite attributes, ultracapacitors and lithium-ion batteries serve different purposes and generally do not overlap in applications. Skeleton and KIT seek to change this by combing them into one solution with all the advantages. The battery part has the high energy density for large-capacity and long-term energy storage, while the capacitor part has the high power density for super-fast charging and can operate across a wide range of temperatures.
Taavi Madiberk, CEO of Skeleton, said that its SuperBattery will be a “game changer for the automotive industry” because it is expected to meet all the functional demands for a powertrain battery (e.g., rapid charging, long service life, and long range). The company has also revealed that it has signed a letter of intent with one of Europe’s leading automotive OEMs to push this innovative technology into the market. The deal is valued around 1 billion euros.
How to put this ideal hybrid design into practice will be a daunting task. After all, there is no lithium-ion battery in existence that can even come close to achieving a 15-second charge. Reports from some news outlets speculate that the capacitor part of the SuperBattery will kick in to provide the power for short-range driving when the battery part runs out of juice. In this scenario, the role of the ultracapacitor is to help EVs get to the next charging station rather than assuming responsibility for a significant portion of the driving range. For now, ultracapacitors still do not appear to be suited for long-distance trips, especially if there are very few charging stations along the routes.
The startup has yet to offer a more detailed explanation on how its technology works, other than mentioning that Curved Graphene is the key in raising the power density and operational lifespan. Proposals for a hybrid energy storage system consisting of an ultracapacitor and a battery have been raised in the recent period as both battery suppliers and carmakers hope to eliminate the shortcomings of conventional lithium-ion batteries. For instance, the leading EV manufacturer Tesla Inc. acquired Maxwell Technologies Inc. last year because the former intends to use the latter’s ultracapacitor technology to support the batteries used in its EVs.
(Photo credit: Skelton Technologies GmbH.)