Development of X-CAP -

the Next Generation of Energy Storage



This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101011162.

Project Aim

For the further acceleration of transport electrification, the cost of energy storage needs to be reduced while also delivering more range, faster charging times and less weight. These opposing goals cannot be met by batteries alone. We propose an alternative, ultracapacitor-derived solution, which can support and replace batteries throughout a multitude of applications.

The X-Cap is a game changer product for the mobility market bridging the gap between power and energy devices to speed up vehicle electrification as well as support further integration of renewables into the electric grid. X-Cap also has the specifications to replace lead acid batteries in most applications.

Ultracapacitors are energy storage devices with much longer lifetime, higher power density and lower environmental impact than Lithium Ion Batteries, but with reduced energy density. Increasing the energy density of Ultracapacitors significantly widens their field of application, but the potential energy density increase is limited.

Within the presented project, a novel energy storage material is to be applied in ultracapacitor cells in order to create a device capable of delivering high power energy storage with increased storage capability beyond the theoretical limit of classical Ultracapacitors.

Project Team


Skeleton Technologies Group employs one of the largest Ultracapacitor development teams globally, consisting of over 25 chemists and physicists, as well as chemical, electrical, and mechanical engineers, including 7 PhDs.

The team has successfully worked on projects ranging from basic material science to applied cell development, material upscaling, and grid systems development.

The project development effort is led by one of the leading experts on the topic of metal oxide-based ultracapacitors, Dr. Daniel Weingarth, who brings in the experience of leading a large research team and a total of over 10 years of experience in industrial ultracapacitor storage technologies.

The overall project team has very strong competence in novel, ALD metal oxide materials, application of these materials in ultracapacitors and electrode piloting, as well as product development for automotive and industrial applications.

Societal Importance


The Großröhrsdorf facility, where the X-Cap will be developed and produced, is located in a former coal mining region in East Germany, near the Czech boarder. Skeleton has chosen this site due to our commitment to further a just energy transition, not only with our technology, but in an effort to bring clean, safe, and permanent jobs to a region in transition.

Beyond this, the X-Cap has the potential to finally remove lead from passenger vehicles due to its perfect power-to-energy ratio, improving the life and health of the 2 million people in the global south currently involved in lead-acid battery recycling. Lead poisoning costs each of these people an estimated 1-2.25 years of disability adjusted lifetime, so removing lead would have a massive impact.


EIC Accelerator


The EIC Accelerator is part of the European Innovation Council (EIC) pilot that supports top-class innovators, entrepreneurs, small companies and scientists with funding opportunities and acceleration services.

The EIC Accelerator supports high-risk, high-potential small and medium-sized enterprises and innovators to help them develop and bring onto the market new innovative products, services and business models that could drive economic growth.

Selected companies receive funding and optional equity and are offered business coaching and mentoring to scale up their innovation idea. They get extra acceleration services to connect with investors, corporates and likeminded entrepreneurs.